mirror of https://github.com/Desuuuu/klipper.git
514 lines
17 KiB
C
514 lines
17 KiB
C
// Stepper pulse schedule compression
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//
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// Copyright (C) 2016 Kevin O'Connor <kevin@koconnor.net>
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//
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// This file may be distributed under the terms of the GNU GPLv3 license.
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//
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// The goal of this code is to take a series of scheduled stepper
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// pulse times and compress them into a handful of commands that can
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// be efficiently transmitted and executed on a microcontroller (mcu).
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// The mcu accepts step pulse commands that take interval, count, and
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// add parameters such that 'count' pulses occur, with each step event
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// calculating the next step event time using:
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// next_wake_time = last_wake_time + interval; interval += add
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// This code is writtin in C (instead of python) for processing
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// efficiency - the repetitive integer math is vastly faster in C.
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#include <math.h> // sqrt
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#include <stddef.h> // offsetof
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#include <stdint.h> // uint32_t
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#include <stdio.h> // fprintf
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#include <stdlib.h> // malloc
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#include <string.h> // memset
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#include "serialqueue.h" // struct queue_message
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#define CHECK_LINES 1
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#define QUEUE_START_SIZE 1024
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struct stepcompress {
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// Buffer management
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uint32_t *queue, *queue_end, *queue_pos, *queue_next;
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// Internal tracking
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uint32_t relclock, max_error;
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// Error checking
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uint32_t errors;
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// Message generation
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uint64_t last_step_clock;
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struct list_head msg_queue;
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uint32_t queue_step_msgid, oid;
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};
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/****************************************************************
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* Queue management
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****************************************************************/
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// Shuffle the internal queue to avoid having to allocate more ram
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static void
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clean_queue(struct stepcompress *sc)
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{
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uint32_t *src = sc->queue_pos, *dest = sc->queue;
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while (src < sc->queue_next)
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*dest++ = *src++ - sc->relclock;
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sc->queue_pos = sc->queue;
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sc->queue_next = dest;
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sc->relclock = 0;
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}
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// Expand the internal queue of step times
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static void
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expand_queue(struct stepcompress *sc, int count)
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{
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int alloc = sc->queue_end - sc->queue;
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if (count + sc->queue_next - sc->queue_pos <= alloc) {
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clean_queue(sc);
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return;
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}
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int pos = sc->queue_pos - sc->queue;
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int next = sc->queue_next - sc->queue;
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if (!alloc)
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alloc = QUEUE_START_SIZE;
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while (next + count > alloc)
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alloc *= 2;
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sc->queue = realloc(sc->queue, alloc * sizeof(*sc->queue));
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sc->queue_end = sc->queue + alloc;
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sc->queue_pos = sc->queue + pos;
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sc->queue_next = sc->queue + next;
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}
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// Check if the internal queue needs to be expanded, and expand if so
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static inline void
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check_expand(struct stepcompress *sc, int count)
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{
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if (sc->queue_next + count > sc->queue_end)
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expand_queue(sc, count);
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}
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/****************************************************************
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* Step compression
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****************************************************************/
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#define DIV_UP(n,d) (((n) + (d) - 1) / (d))
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static inline int32_t
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idiv_up(int32_t n, int32_t d)
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{
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return (n>=0) ? DIV_UP(n,d) : (n/d);
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}
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static inline int32_t
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idiv_down(int32_t n, int32_t d)
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{
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return (n>=0) ? (n/d) : (n - d + 1) / d;
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}
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struct points {
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int32_t minp, maxp;
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};
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// Given a requested step time, return the minimum and maximum
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// acceptable times
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static struct points
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minmax_point(struct stepcompress *sc, uint32_t *pos)
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{
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uint32_t prevpoint = pos > sc->queue_pos ? *(pos-1) - sc->relclock : 0;
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uint32_t point = *pos - sc->relclock;
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uint32_t max_error = (point - prevpoint) / 2;
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if (max_error > sc->max_error)
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max_error = sc->max_error;
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return (struct points){ point - max_error, point };
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}
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// The maximum add delta between two valid quadratic sequences of the
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// form "add*count*(count-1)/2 + interval*count" is "(6 + 4*sqrt(2)) *
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// maxerror / (count*count)". The "6 + 4*sqrt(2)" is 11.65685, but
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// using 11 and rounding up when dividing works well in practice.
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#define QUADRATIC_DEV 11
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struct step_move {
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uint32_t interval;
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uint16_t count;
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int16_t add;
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};
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// Find a 'step_move' that covers a series of step times
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static struct step_move
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compress_bisect_add(struct stepcompress *sc)
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{
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uint32_t *last = sc->queue_next;
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if (last > sc->queue_pos + 65535)
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last = sc->queue_pos + 65535;
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struct points point = minmax_point(sc, sc->queue_pos);
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int32_t origmininterval = point.minp, origmaxinterval = point.maxp;
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int32_t add = 0, minadd=-0x8001, maxadd=0x8000;
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int32_t bestadd=0, bestcount=0, bestinterval=0;
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for (;;) {
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// Find longest valid sequence with the given 'add'
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int32_t mininterval = origmininterval, maxinterval = origmaxinterval;
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int32_t count = 1, addfactor = 0;
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for (;;) {
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if (sc->queue_pos + count >= last)
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return (struct step_move){ maxinterval, count, add };
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point = minmax_point(sc, sc->queue_pos + count);
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addfactor += count;
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int32_t c = add*addfactor;
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int32_t nextmininterval = mininterval;
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if (c + nextmininterval*(count+1) < point.minp)
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nextmininterval = DIV_UP(point.minp - c, count+1);
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int32_t nextmaxinterval = maxinterval;
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if (c + nextmaxinterval*(count+1) > point.maxp)
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nextmaxinterval = (point.maxp - c) / (count+1);
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if (nextmininterval > nextmaxinterval)
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break;
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count += 1;
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mininterval = nextmininterval;
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maxinterval = nextmaxinterval;
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}
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if (count > bestcount || (count == bestcount && add > bestadd)) {
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bestcount = count;
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bestadd = add;
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bestinterval = maxinterval;
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}
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// Check if a greater or lesser add could extend the sequence
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int32_t maxreach = add*addfactor + maxinterval*(count+1);
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if (maxreach < point.minp) {
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minadd = add;
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origmaxinterval = maxinterval;
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} else {
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maxadd = add;
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origmininterval = mininterval;
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}
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// See if next point would further limit the add range
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if ((minadd+1)*addfactor + origmaxinterval*(count+1) < point.minp)
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minadd = idiv_up(point.minp - origmaxinterval*(count+1)
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, addfactor) - 1;
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if ((maxadd-1)*addfactor + origmininterval*(count+1) > point.maxp)
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maxadd = idiv_down(point.maxp - origmininterval*(count+1)
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, addfactor) + 1;
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// The maximum valid deviation between two quadratic sequences
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// can be calculated and used to further limit the add range.
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if (count > 1) {
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int32_t errdelta = DIV_UP(sc->max_error*QUADRATIC_DEV, count*count);
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if (minadd < add - errdelta)
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minadd = add - errdelta;
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if (maxadd > add + errdelta)
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maxadd = add + errdelta;
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}
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// Bisect valid add range and try again with new 'add'
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add = (maxadd + minadd) / 2;
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if (add <= minadd || add >= maxadd)
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break;
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}
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if (bestcount < 2)
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bestadd = 0;
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return (struct step_move){ bestinterval, bestcount, bestadd };
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}
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/****************************************************************
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* Step compress checking
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****************************************************************/
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// Verify that a given 'step_move' matches the actual step times
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static void
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check_line(struct stepcompress *sc, struct step_move move)
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{
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if (!CHECK_LINES)
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return;
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int err = 0;
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if (!move.count || !move.interval || move.interval >= 0x80000000) {
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fprintf(stderr, "ERROR: Point out of range: %d %d %d\n"
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, move.interval, move.count, move.add);
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err++;
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}
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uint32_t interval = move.interval, p = interval;
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uint16_t i;
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for (i=0; i<move.count; i++) {
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struct points point = minmax_point(sc, sc->queue_pos + i);
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if (p < point.minp || p > point.maxp) {
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fprintf(stderr, "ERROR: Point %d of %d: %d not in %d:%d\n"
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, i+1, move.count, p, point.minp, point.maxp);
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err++;
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}
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interval += move.add;
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p += interval;
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}
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sc->errors += err;
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}
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/****************************************************************
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* Step compress interface
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****************************************************************/
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// Allocate a new 'stepcompress' object
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struct stepcompress *
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stepcompress_alloc(uint32_t max_error, uint32_t queue_step_msgid, uint32_t oid)
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{
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struct stepcompress *sc = malloc(sizeof(*sc));
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memset(sc, 0, sizeof(*sc));
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sc->max_error = max_error;
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list_init(&sc->msg_queue);
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sc->queue_step_msgid = queue_step_msgid;
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sc->oid = oid;
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return sc;
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}
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// Schedule a step event at the specified step_clock time
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void
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stepcompress_push(struct stepcompress *sc, double step_clock)
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{
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check_expand(sc, 1);
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step_clock += 0.5 + sc->relclock - sc->last_step_clock;
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*sc->queue_next++ = step_clock;
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}
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// Schedule 'steps' number of steps with a constant time between steps
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// using the formula: step_clock = clock_offset + step_num*factor
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double
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stepcompress_push_factor(struct stepcompress *sc
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, double steps, double step_offset
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, double clock_offset, double factor)
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{
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// Calculate number of steps to take
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double ceil_steps = ceil(steps - step_offset);
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double next_step_offset = ceil_steps - (steps - step_offset);
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int count = ceil_steps;
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if (count < 0 || count > 1000000) {
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fprintf(stderr, "ERROR: push_factor invalid count %d %f %f %f %f\n"
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, sc->oid, steps, step_offset, clock_offset, factor);
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return next_step_offset;
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}
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check_expand(sc, count);
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// Calculate each step time
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uint32_t *qn = sc->queue_next, *end = &qn[count];
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clock_offset += 0.5 + sc->relclock - sc->last_step_clock;
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double pos = step_offset;
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while (qn < end) {
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*qn++ = clock_offset + pos*factor;
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pos += 1.0;
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}
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sc->queue_next = qn;
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return next_step_offset;
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}
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// Schedule 'steps' number of steps using the formula:
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// step_clock = clock_offset + sqrt(step_num*factor + sqrt_offset)
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double
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stepcompress_push_sqrt(struct stepcompress *sc, double steps, double step_offset
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, double clock_offset, double sqrt_offset, double factor)
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{
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// Calculate number of steps to take
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double ceil_steps = ceil(steps - step_offset);
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double next_step_offset = ceil_steps - (steps - step_offset);
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int count = ceil_steps;
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if (count < 0 || count > 1000000) {
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fprintf(stderr, "ERROR: push_sqrt invalid count %d %f %f %f %f %f\n"
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, sc->oid, steps, step_offset, clock_offset, sqrt_offset
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, factor);
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return next_step_offset;
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}
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check_expand(sc, count);
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// Calculate each step time
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uint32_t *qn = sc->queue_next, *end = &qn[count];
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clock_offset += 0.5 + sc->relclock - sc->last_step_clock;
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double pos = step_offset + sqrt_offset/factor;
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if (factor >= 0.0)
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while (qn < end) {
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*qn++ = clock_offset + sqrt(pos*factor);
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pos += 1.0;
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}
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else
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while (qn < end) {
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*qn++ = clock_offset - sqrt(pos*factor);
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pos += 1.0;
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}
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sc->queue_next = qn;
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return next_step_offset;
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}
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// Convert previously scheduled steps into commands for the mcu
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static void
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stepcompress_flush(struct stepcompress *sc, uint64_t move_clock)
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{
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if (sc->queue_pos >= sc->queue_next)
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return;
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while (move_clock > sc->last_step_clock) {
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struct step_move move = compress_bisect_add(sc);
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check_line(sc, move);
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uint32_t msg[5] = {
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sc->queue_step_msgid, sc->oid, move.interval, move.count, move.add
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};
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struct queue_message *qm = message_alloc_and_encode(msg, 5);
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qm->req_clock = sc->last_step_clock;
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list_add_tail(&qm->node, &sc->msg_queue);
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uint32_t addfactor = move.count*(move.count-1)/2;
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uint32_t ticks = move.add*addfactor + move.interval*move.count;
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sc->last_step_clock += ticks;
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if (sc->queue_pos + move.count >= sc->queue_next) {
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sc->queue_pos = sc->queue_next = sc->queue;
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sc->relclock = 0;
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break;
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}
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sc->queue_pos += move.count;
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sc->relclock += ticks;
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}
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}
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// Reset the internal state of the stepcompress object
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void
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stepcompress_reset(struct stepcompress *sc, uint64_t last_step_clock)
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{
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stepcompress_flush(sc, UINT64_MAX);
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sc->last_step_clock = last_step_clock;
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}
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// Queue an mcu command to go out in order with stepper commands
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void
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stepcompress_queue_msg(struct stepcompress *sc, uint32_t *data, int len)
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{
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stepcompress_flush(sc, UINT64_MAX);
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struct queue_message *qm = message_alloc_and_encode(data, len);
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qm->min_clock = -1;
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qm->req_clock = sc->last_step_clock;
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list_add_tail(&qm->node, &sc->msg_queue);
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}
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// Return the count of internal errors found
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uint32_t
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stepcompress_get_errors(struct stepcompress *sc)
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{
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return sc->errors;
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}
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/****************************************************************
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* Step compress synchronization
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****************************************************************/
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// The steppersync object is used to synchronize the output of mcu
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// step commands. The mcu can only queue a limited number of step
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// commands - this code tracks when items on the mcu step queue become
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// free so that new commands can be transmitted. It also ensures the
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// mcu step queue is ordered between steppers so that no stepper
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// starves the other steppers of space in the mcu step queue.
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struct steppersync {
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// Serial port
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struct serialqueue *sq;
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struct command_queue *cq;
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// Storage for associated stepcompress objects
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struct stepcompress **sc_list;
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int sc_num;
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// Storage for list of pending move clocks
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uint64_t *move_clocks;
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int num_move_clocks;
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};
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// Allocate a new 'steppersync' object
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struct steppersync *
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steppersync_alloc(struct serialqueue *sq, struct stepcompress **sc_list
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, int sc_num, int move_num)
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{
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struct steppersync *ss = malloc(sizeof(*ss));
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memset(ss, 0, sizeof(*ss));
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ss->sq = sq;
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ss->cq = serialqueue_alloc_commandqueue();
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ss->sc_list = malloc(sizeof(*sc_list)*sc_num);
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memcpy(ss->sc_list, sc_list, sizeof(*sc_list)*sc_num);
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ss->sc_num = sc_num;
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ss->move_clocks = malloc(sizeof(*ss->move_clocks)*move_num);
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memset(ss->move_clocks, 0, sizeof(*ss->move_clocks)*move_num);
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ss->num_move_clocks = move_num;
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return ss;
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}
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// Implement a binary heap algorithm to track when the next available
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// 'struct move' in the mcu will be available
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static void
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heap_replace(struct steppersync *ss, uint64_t req_clock)
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{
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uint64_t *mc = ss->move_clocks;
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int nmc = ss->num_move_clocks, pos = 0;
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for (;;) {
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int child1_pos = 2*pos+1, child2_pos = 2*pos+2;
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uint64_t child2_clock = child2_pos < nmc ? mc[child2_pos] : UINT64_MAX;
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uint64_t child1_clock = child1_pos < nmc ? mc[child1_pos] : UINT64_MAX;
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if (req_clock <= child1_clock && req_clock <= child2_clock) {
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mc[pos] = req_clock;
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break;
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}
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if (child1_clock < child2_clock) {
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mc[pos] = child1_clock;
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pos = child1_pos;
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} else {
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mc[pos] = child2_clock;
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pos = child2_pos;
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}
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}
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}
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// Find and transmit any scheduled steps prior to the given 'move_clock'
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void
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steppersync_flush(struct steppersync *ss, uint64_t move_clock)
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{
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// Flush each stepcompress to the specified move_clock
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int i;
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for (i=0; i<ss->sc_num; i++)
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stepcompress_flush(ss->sc_list[i], move_clock);
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// Order commands by the reqclock of each pending command
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struct list_head msgs;
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list_init(&msgs);
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uint64_t min_clock = ss->move_clocks[0];
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for (;;) {
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// Find message with lowest reqclock
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uint64_t req_clock = MAX_CLOCK;
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struct queue_message *qm = NULL;
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for (i=0; i<ss->sc_num; i++) {
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struct stepcompress *sc = ss->sc_list[i];
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if (!list_empty(&sc->msg_queue)) {
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struct queue_message *m = list_first_entry(
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&sc->msg_queue, struct queue_message, node);
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if (m->req_clock < req_clock) {
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qm = m;
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req_clock = m->req_clock;
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}
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}
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}
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if (!qm || (!qm->min_clock && req_clock > move_clock))
|
|
break;
|
|
|
|
// Set the min_clock for this command
|
|
if (!qm->min_clock) {
|
|
qm->min_clock = min_clock;
|
|
heap_replace(ss, req_clock);
|
|
min_clock = ss->move_clocks[0];
|
|
} else {
|
|
qm->min_clock = min_clock;
|
|
}
|
|
|
|
// Batch this command
|
|
list_del(&qm->node);
|
|
list_add_tail(&qm->node, &msgs);
|
|
}
|
|
|
|
// Transmit commands
|
|
if (!list_empty(&msgs))
|
|
serialqueue_send_batch(ss->sq, ss->cq, &msgs);
|
|
}
|