From 7c8addc5c5f811eefbed901fcd182a3012e2e75b Mon Sep 17 00:00:00 2001
From: Kevin O'Connor <kevin@koconnor.net>
Date: Wed, 2 Nov 2016 17:30:34 -0400
Subject: [PATCH] gpio: Merge gpio_adc_sample_time() into gpio_adc_sample()

Return the number of clock ticks to wait directly from
gpio_adc_sample().  This simplifies the ADC interface.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
---
 src/adccmds.c        |  9 +++++----
 src/avr/gpio.c       | 34 +++++++++++++++++-----------------
 src/avr/gpio.h       |  6 ++----
 src/generic/gpio.h   |  5 ++---
 src/simulator/gpio.c |  9 +++------
 5 files changed, 29 insertions(+), 34 deletions(-)

diff --git a/src/adccmds.c b/src/adccmds.c
index 9c70ab88..907e05d4 100644
--- a/src/adccmds.c
+++ b/src/adccmds.c
@@ -22,8 +22,9 @@ static uint8_t
 analog_in_event(struct timer *timer)
 {
     struct analog_in *a = container_of(timer, struct analog_in, timer);
-    if (gpio_adc_sample(a->pin)) {
-        a->timer.waketime += gpio_adc_sample_time();
+    uint32_t sample_delay = gpio_adc_sample(a->pin);
+    if (sample_delay) {
+        a->timer.waketime += sample_delay;
         return SF_RESCHEDULE;
     }
     uint16_t value = gpio_adc_read(a->pin);
@@ -62,7 +63,7 @@ command_query_analog_in(uint32_t *args)
 {
     struct analog_in *a = lookup_oid(args[0], command_config_analog_in);
     sched_del_timer(&a->timer);
-    gpio_adc_clear_sample(a->pin);
+    gpio_adc_cancel_sample(a->pin);
     a->next_begin_time = args[1];
     a->timer.waketime = a->next_begin_time;
     a->sample_time = args[2];
@@ -111,7 +112,7 @@ analog_in_shutdown(void)
     uint8_t i;
     struct analog_in *a;
     foreach_oid(i, a, command_config_analog_in) {
-        gpio_adc_clear_sample(a->pin);
+        gpio_adc_cancel_sample(a->pin);
     }
 }
 DECL_SHUTDOWN(analog_in_shutdown);
diff --git a/src/avr/gpio.c b/src/avr/gpio.c
index 9919cdd1..3df6e9e8 100644
--- a/src/avr/gpio.c
+++ b/src/avr/gpio.c
@@ -282,27 +282,24 @@ gpio_adc_setup(uint8_t pin)
     shutdown("Not a valid ADC pin");
 }
 
-uint32_t
-gpio_adc_sample_time(void)
-{
-    return (13 + 1) * 128 + 200;
-}
-
 enum { ADC_DUMMY=0xff };
 static uint8_t last_analog_read = ADC_DUMMY;
 
-uint8_t
+// Try to sample a value. Returns zero if sample ready, otherwise
+// returns the number of clock ticks the caller should wait before
+// retrying this function.
+uint32_t
 gpio_adc_sample(struct gpio_adc g)
 {
     if (ADCSRA & (1<<ADSC))
         // Busy
-        return 1;
+        goto need_delay;
     if (last_analog_read == g.chan)
         // Sample now ready
         return 0;
     if (last_analog_read != ADC_DUMMY)
         // Sample on another channel in progress
-        return 1;
+        goto need_delay;
     last_analog_read = g.chan;
 
 #if defined(ADCSRB) && defined(MUX5)
@@ -315,16 +312,11 @@ gpio_adc_sample(struct gpio_adc g)
 
     // start the conversion
     ADCSRA |= 1<<ADSC;
-    return 1;
-}
-
-void
-gpio_adc_clear_sample(struct gpio_adc g)
-{
-    if (last_analog_read == g.chan)
-        last_analog_read = ADC_DUMMY;
+need_delay:
+    return (13 + 1) * 128 + 200;
 }
 
+// Read a value; use only after gpio_adc_sample() returns zero
 uint16_t
 gpio_adc_read(struct gpio_adc g)
 {
@@ -332,6 +324,14 @@ gpio_adc_read(struct gpio_adc g)
     return ADC;
 }
 
+// Cancel a sample that may have been started with gpio_adc_sample()
+void
+gpio_adc_cancel_sample(struct gpio_adc g)
+{
+    if (last_analog_read == g.chan)
+        last_analog_read = ADC_DUMMY;
+}
+
 
 void
 spi_config(void)
diff --git a/src/avr/gpio.h b/src/avr/gpio.h
index e6cbbd32..4eb37204 100644
--- a/src/avr/gpio.h
+++ b/src/avr/gpio.h
@@ -2,7 +2,6 @@
 #define __AVR_GPIO_H
 
 #include <stdint.h>
-#include "compiler.h" // __always_inline
 
 struct gpio_out {
     struct gpio_digital_regs *regs;
@@ -31,10 +30,9 @@ struct gpio_adc {
     uint8_t chan;
 };
 struct gpio_adc gpio_adc_setup(uint8_t pin);
-uint32_t gpio_adc_sample_time(void);
-uint8_t gpio_adc_sample(struct gpio_adc g);
-void gpio_adc_clear_sample(struct gpio_adc g);
+uint32_t gpio_adc_sample(struct gpio_adc g);
 uint16_t gpio_adc_read(struct gpio_adc g);
+void gpio_adc_cancel_sample(struct gpio_adc g);
 
 void spi_config(void);
 void spi_transfer(char *data, uint8_t len);
diff --git a/src/generic/gpio.h b/src/generic/gpio.h
index 07307b9e..4b5dc812 100644
--- a/src/generic/gpio.h
+++ b/src/generic/gpio.h
@@ -26,10 +26,9 @@ struct gpio_adc {
     uint8_t pin;
 };
 struct gpio_adc gpio_adc_setup(uint8_t pin);
-uint32_t gpio_adc_sample_time(void);
-uint8_t gpio_adc_sample(struct gpio_adc g);
-void gpio_adc_clear_sample(struct gpio_adc g);
+uint32_t gpio_adc_sample(struct gpio_adc g);
 uint16_t gpio_adc_read(struct gpio_adc g);
+void gpio_adc_cancel_sample(struct gpio_adc g);
 
 void spi_config(void);
 void spi_transfer(char *data, uint8_t len);
diff --git a/src/simulator/gpio.c b/src/simulator/gpio.c
index 6e89f946..569f4b78 100644
--- a/src/simulator/gpio.c
+++ b/src/simulator/gpio.c
@@ -27,17 +27,14 @@ void gpio_pwm_write(struct gpio_pwm g, uint8_t val) {
 struct gpio_adc gpio_adc_setup(uint8_t pin) {
     return (struct gpio_adc){.pin=pin};
 }
-uint32_t gpio_adc_sample_time(void) {
+uint32_t gpio_adc_sample(struct gpio_adc g) {
     return 0;
 }
-uint8_t gpio_adc_sample(struct gpio_adc g) {
-    return 0;
-}
-void gpio_adc_clear_sample(struct gpio_adc g) {
-}
 uint16_t gpio_adc_read(struct gpio_adc g) {
     return 0;
 }
+void gpio_adc_cancel_sample(struct gpio_adc g) {
+}
 
 void spi_config(void) {
 }