pbio/drv/adc: Use microseconds for settling time delay.

A full ADC roundtrip is now close to 80 us, so we don't need to wait 2ms. This also avoids rounding errors where you might sometimes wait a whole millisecond longer.

Also use pbio_os_timer_extend in the ADC loop for more constant loop time.

Combined with previous runloop improvements, this makes the RGB light on the NXT Color Sensor blink without visual stutters. See pybricks/support#2301

Author: laurensvalk

lib/pbio/drv/adc/adc_stm32_hal.c

@@ -47,8 +47,8 @@ static uint32_t pbdrv_adc_last_error;
 
 PROCESS(pbdrv_adc_process, "ADC");
 
-pbio_error_t pbdrv_adc_await_new_samples(pbio_os_state_t *state, pbio_os_timer_t *timer, uint32_t future) {
-    return PBIO_ERROR_NOT_SUPPORTED;
+pbio_error_t pbdrv_adc_await_new_samples(pbio_os_state_t *state, uint32_t *start_time_us, uint32_t future_us) {
+    return PBIO_ERROR_NOT_IMPLEMENTED;
 }
 
 pbio_error_t pbdrv_adc_get_ch(uint8_t ch, uint16_t *value) {

lib/pbio/drv/adc/adc_stm32f0.c

@@ -66,8 +66,8 @@ void pbdrv_adc_init(void) {
     process_start(&pbdrv_adc_process);
 }
 
-pbio_error_t pbdrv_adc_await_new_samples(pbio_os_state_t *state, pbio_os_timer_t *timer, uint32_t future) {
-    return PBIO_ERROR_NOT_SUPPORTED;
+pbio_error_t pbdrv_adc_await_new_samples(pbio_os_state_t *state, uint32_t *start_time_us, uint32_t future_us) {
+    return PBIO_ERROR_NOT_IMPLEMENTED;
 }
 
 // does a single conversion for the specified channel

lib/pbio/drv/block_device/block_device_ev3.c

@@ -116,7 +116,7 @@ static struct {
     uint8_t rx_dummy_byte;
 } spi_dev_bufs PBDRV_DMA_BUF;
 
-static uint32_t last_spi_dma_complete_time;
+static uint32_t last_spi_dma_complete_time_us;
 
 static void spi_dma_complete(void) {
     // Only complete once RX and TX complete.
@@ -129,7 +129,7 @@ static void spi_dma_complete(void) {
     if (spi_dev.rx_user_buf_addr && spi_dev.rx_user_buf_sz) {
         pbdrv_cache_prepare_after_dma((void *)spi_dev.rx_user_buf_addr, spi_dev.rx_user_buf_sz);
     }
-    last_spi_dma_complete_time = pbdrv_clock_get_ms();
+    last_spi_dma_complete_time_us = pbdrv_clock_get_us();
 }
 
 /**
@@ -764,10 +764,10 @@ pbio_error_t pbdrv_adc_get_ch(uint8_t ch, uint16_t *value) {
     return PBIO_SUCCESS;
 }
 
-pbio_error_t pbdrv_adc_await_new_samples(pbio_os_state_t *state, pbio_os_timer_t *timer, uint32_t future) {
+pbio_error_t pbdrv_adc_await_new_samples(pbio_os_state_t *state, uint32_t *start_time_us, uint32_t future_us) {
     PBIO_OS_ASYNC_BEGIN(state);
-    pbio_os_timer_set(timer, 0);
-    PBIO_OS_AWAIT_UNTIL(state, pbio_util_time_has_passed(last_spi_dma_complete_time, timer->start + future));
+    *start_time_us = pbdrv_clock_get_us();
+    PBIO_OS_AWAIT_UNTIL(state, pbio_util_time_has_passed(last_spi_dma_complete_time_us, *start_time_us + future_us));
     PBIO_OS_ASYNC_END(PBIO_SUCCESS);
 }
 
@@ -916,6 +916,8 @@ pbio_error_t ev3_spi_process_thread(pbio_os_state_t *state, void *context) {
     pbdrv_block_device_load_err = err;
     pbio_busy_count_down();
 
+    pbio_os_timer_set(&timer, ADC_SAMPLE_PERIOD);
+
     // Poll ADC continuously until cancellation is requested.
     while (!(ev3_spi_process.request & PBIO_OS_PROCESS_REQUEST_TYPE_CANCEL)) {
 
@@ -928,8 +930,8 @@ pbio_error_t ev3_spi_process_thread(pbio_os_state_t *state, void *context) {
         // Await for transfer to complete.
         PBIO_OS_AWAIT_WHILE(state, (spi_dev.status & SPI_STATUS_WAIT_ANY));
 
-        pbio_os_timer_set(&timer, ADC_SAMPLE_PERIOD);
-        PBIO_OS_AWAIT_UNTIL(state, ev3_spi_process.request || pbio_os_timer_is_expired(&timer));
+        PBIO_OS_AWAIT_UNTIL(state, pbio_os_timer_is_expired(&timer));
+        pbio_os_timer_extend(&timer);
     }
 
     // Now that the ADC loop has ended, we can use the SPI bus to save user

lib/pbio/include/pbdrv/adc.h

@@ -34,11 +34,11 @@ pbio_error_t pbdrv_adc_get_ch(uint8_t ch, uint16_t *value);
  *
  * Not implemented on all platforms.
  *
- * @param [in] state    Protothread state.
- * @param [in] timer    Parent process timer, used to store time of calling this.
- * @param [in] future   How far into the future the sample should be (ms).
+ * @param [in]  state          Protothread state.
+ * @param [out] start_time_us  Persistent value used by this function to store the start time (µs).
+ * @param [in]  future_us      How far into the future the sample should be (µs).
  */
-pbio_error_t pbdrv_adc_await_new_samples(pbio_os_state_t *state, pbio_os_timer_t *timer, uint32_t future);
+pbio_error_t pbdrv_adc_await_new_samples(pbio_os_state_t *state, uint32_t *start_time_us, uint32_t future_us);
 
 #else
 
@@ -47,7 +47,7 @@ static inline pbio_error_t pbdrv_adc_get_ch(uint8_t ch, uint16_t *value) {
     return PBIO_ERROR_NOT_SUPPORTED;
 }
 
-static inline pbio_error_t pbdrv_adc_await_new_samples(pbio_os_state_t *state, pbio_os_timer_t *timer, uint32_t future) {
+static inline pbio_error_t pbdrv_adc_await_new_samples(pbio_os_state_t *state, uint32_t *start_time_us, uint32_t future_us) {
     return PBIO_ERROR_NOT_SUPPORTED;
 }
 

lib/pbio/src/port_dcm_ev3.c

@@ -374,12 +374,12 @@ pbio_error_t pbio_port_dcm_thread(pbio_os_state_t *state, pbio_os_timer_t *timer
             while (!pbdrv_gpio_input(&pins->p2)) {
                 // Reflected intensity.
                 pbdrv_gpio_out_high(&pins->p5);
-                PBIO_OS_AWAIT(state, &dcm->child, pbdrv_adc_await_new_samples(&dcm->child, timer, 2));
+                PBIO_OS_AWAIT(state, &dcm->child, pbdrv_adc_await_new_samples(&dcm->child, &timer->start, 200));
                 dcm->nxt_rgba.r = pbio_port_dcm_get_mv(pins, 1);
 
                 // Ambient intensity.
                 pbdrv_gpio_out_low(&pins->p5);
-                PBIO_OS_AWAIT(state, &dcm->child, pbdrv_adc_await_new_samples(&dcm->child, timer, 2));
+                PBIO_OS_AWAIT(state, &dcm->child, pbdrv_adc_await_new_samples(&dcm->child, &timer->start, 200));
                 dcm->nxt_rgba.a = pbio_port_dcm_get_mv(pins, 1);
             }
             continue;
@@ -410,19 +410,19 @@ pbio_error_t pbio_port_dcm_thread(pbio_os_state_t *state, pbio_os_timer_t *timer
             while (!pbdrv_gpio_input(&pins->p2)) {
 
                 pbdrv_gpio_out_low(&pins->p5);
-                PBIO_OS_AWAIT(state, &dcm->child, pbdrv_adc_await_new_samples(&dcm->child, timer, 2));
+                PBIO_OS_AWAIT(state, &dcm->child, pbdrv_adc_await_new_samples(&dcm->child, &timer->start, 200));
                 dcm->nxt_rgba.a = pbio_port_dcm_get_mv(pins, 6);
 
                 pbdrv_gpio_out_high(&pins->p5);
-                PBIO_OS_AWAIT(state, &dcm->child, pbdrv_adc_await_new_samples(&dcm->child, timer, 2));
+                PBIO_OS_AWAIT(state, &dcm->child, pbdrv_adc_await_new_samples(&dcm->child, &timer->start, 200));
                 dcm->nxt_rgba.r = pbio_port_dcm_get_mv(pins, 6);
 
                 pbdrv_gpio_out_low(&pins->p5);
-                PBIO_OS_AWAIT(state, &dcm->child, pbdrv_adc_await_new_samples(&dcm->child, timer, 2));
+                PBIO_OS_AWAIT(state, &dcm->child, pbdrv_adc_await_new_samples(&dcm->child, &timer->start, 2000));
                 dcm->nxt_rgba.g = pbio_port_dcm_get_mv(pins, 6);
 
                 pbdrv_gpio_out_high(&pins->p5);
-                PBIO_OS_AWAIT(state, &dcm->child, pbdrv_adc_await_new_samples(&dcm->child, timer, 2));
+                PBIO_OS_AWAIT(state, &dcm->child, pbdrv_adc_await_new_samples(&dcm->child, &timer->start, 200));
                 dcm->nxt_rgba.b = pbio_port_dcm_get_mv(pins, 6);
             }
             pbdrv_gpio_out_low(&pins->p5);