lcd_hd44780: Add micro-controller code for the HD44780 LCD chip

Add support for passing messages to an HD44780 chip via a 4-bit
bit-banging interface.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor 2018-02-20 20:48:26 -05:00
parent 9140f36d99
commit afc9bcf27b
2 changed files with 133 additions and 1 deletions

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@ -5,4 +5,4 @@ src-$(CONFIG_HAVE_GPIO) += gpiocmds.c stepper.c endstop.c
src-$(CONFIG_HAVE_GPIO_ADC) += adccmds.c
src-$(CONFIG_HAVE_GPIO_SPI) += spicmds.c
src-$(CONFIG_HAVE_GPIO_HARD_PWM) += pwmcmds.c
src-$(CONFIG_HAVE_USER_INTERFACE) += lcd_st7920.c
src-$(CONFIG_HAVE_USER_INTERFACE) += lcd_st7920.c lcd_hd44780.c

132
src/lcd_hd44780.c Normal file
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@ -0,0 +1,132 @@
// Commands for sending messages to a 4-bit hd44780 lcd driver
//
// Copyright (C) 2018 Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include "basecmd.h" // oid_alloc
#include "board/gpio.h" // gpio_out_write
#include "board/irq.h" // irq_disable
#include "board/misc.h" // timer_from_us
#include "command.h" // DECL_COMMAND
#include "sched.h" // DECL_SHUTDOWN
struct hd44780 {
uint32_t last_cmd_time, cmd_wait_ticks;
uint8_t last;
struct gpio_out rs, e, d4, d5, d6, d7;
};
/****************************************************************
* Transmit functions
****************************************************************/
// Write 4 bits to the hd44780 using the 4bit parallel interface
static __always_inline void
hd44780_xmit_bits(uint8_t toggle, struct gpio_out e, struct gpio_out d4
, struct gpio_out d5, struct gpio_out d6, struct gpio_out d7)
{
gpio_out_toggle(e);
if (toggle & 0x10)
gpio_out_toggle(d4);
if (toggle & 0x20)
gpio_out_toggle(d5);
if (toggle & 0x40)
gpio_out_toggle(d6);
if (toggle & 0x80)
gpio_out_toggle(d7);
gpio_out_toggle(e);
}
// Transmit 8 bits to the chip
static void
hd44780_xmit_byte(struct hd44780 *h, uint8_t data)
{
struct gpio_out e = h->e, d4 = h->d4, d5 = h->d5, d6 = h->d6, d7 = h->d7;
hd44780_xmit_bits(h->last ^ data, e, d4, d5, d6, d7);
h->last = data << 4;
hd44780_xmit_bits(data ^ h->last, e, d4, d5, d6, d7);
}
// Transmit a series of bytes to the chip
static void
hd44780_xmit(struct hd44780 *h, uint8_t len, uint8_t *data)
{
uint32_t last_cmd_time=h->last_cmd_time, cmd_wait_ticks=h->cmd_wait_ticks;
while (len--) {
uint8_t b = *data++;
while (timer_read_time() - last_cmd_time < cmd_wait_ticks)
irq_poll();
hd44780_xmit_byte(h, b);
last_cmd_time = timer_read_time();
}
h->last_cmd_time = last_cmd_time;
}
/****************************************************************
* Interface
****************************************************************/
void
command_config_hd44780(uint32_t *args)
{
struct hd44780 *h = oid_alloc(args[0], command_config_hd44780, sizeof(*h));
h->rs = gpio_out_setup(args[1], 0);
h->e = gpio_out_setup(args[2], 0);
h->d4 = gpio_out_setup(args[3], 0);
h->d5 = gpio_out_setup(args[4], 0);
h->d6 = gpio_out_setup(args[5], 0);
h->d7 = gpio_out_setup(args[6], 0);
// Calibrate cmd_wait_ticks
irq_disable();
uint32_t start = timer_read_time();
hd44780_xmit_byte(h, 0);
uint32_t end = timer_read_time();
irq_enable();
uint32_t diff = end - start, delay_ticks = args[7];
if (delay_ticks > diff)
h->cmd_wait_ticks = delay_ticks - diff;
}
DECL_COMMAND(command_config_hd44780,
"config_hd44780 oid=%c rs_pin=%u e_pin=%u"
" d4_pin=%u d5_pin=%u d6_pin=%u d7_pin=%u delay_ticks=%u");
void
command_hd44780_send_cmds(uint32_t *args)
{
struct hd44780 *h = oid_lookup(args[0], command_config_hd44780);
gpio_out_write(h->rs, 0);
uint8_t len = args[1], *cmds = (void*)(size_t)args[2];
hd44780_xmit(h, len, cmds);
}
DECL_COMMAND(command_hd44780_send_cmds, "hd44780_send_cmds oid=%c cmds=%*s");
void
command_hd44780_send_data(uint32_t *args)
{
struct hd44780 *h = oid_lookup(args[0], command_config_hd44780);
gpio_out_write(h->rs, 1);
uint8_t len = args[1], *data = (void*)(size_t)args[2];
hd44780_xmit(h, len, data);
}
DECL_COMMAND(command_hd44780_send_data, "hd44780_send_data oid=%c data=%*s");
void
hd44780_shutdown(void)
{
uint8_t i;
struct hd44780 *h;
foreach_oid(i, h, command_config_hd44780) {
gpio_out_write(h->rs, 0);
gpio_out_write(h->e, 0);
gpio_out_write(h->d4, 0);
gpio_out_write(h->d5, 0);
gpio_out_write(h->d6, 0);
gpio_out_write(h->d7, 0);
h->last = 0;
}
}
DECL_SHUTDOWN(hd44780_shutdown);