altos/stmf0: Re-implement fast ADC code for stmf0

This creates a ring buffer for ADC data so that ADC fetching can run
in parallel with other activities.

Signed-off-by: Keith Packard <keithp@keithp.com>

4 files changed, 91 insertions, 24 deletions

diff --git a/src/kernel/ao.h b/src/kernel/ao.h
index 16d600aa..59a469ae 100644
--- a/src/kernel/ao.h
+++ b/src/kernel/ao.h
@@ -72,6 +72,7 @@ typedef AO_PORT_TYPE ao_port_t;
 #define AO_PANIC_BUFIO		15	/* Mis-using bufio API */
 #define AO_PANIC_EXTI		16	/* Mis-using exti API */
 #define AO_PANIC_FAST_TIMER	17	/* Mis-using fast timer API */
+#define AO_PANIC_ADC		18	/* Mis-using ADC interface */
 #define AO_PANIC_SELF_TEST_CC1120	0x40 | 1	/* Self test failure */
 #define AO_PANIC_SELF_TEST_HMC5883	0x40 | 2	/* Self test failure */
 #define AO_PANIC_SELF_TEST_MPU6000	0x40 | 3	/* Self test failure */
diff --git a/src/stmf0/ao_adc_fast.c b/src/stmf0/ao_adc_fast.c
index 5885ae4f..be9b5986 100644
--- a/src/stmf0/ao_adc_fast.c
+++ b/src/stmf0/ao_adc_fast.c
@@ -18,7 +18,10 @@
 #include <ao.h>
 #include <ao_adc_fast.h>
 
-static uint8_t			ao_adc_done;
+uint16_t ao_adc_ring[AO_ADC_RING_SIZE];
+
+uint16_t ao_adc_ring_head, ao_adc_ring_tail;
+uint8_t ao_adc_running;
 
 /*
  * Callback from DMA ISR
@@ -28,22 +31,30 @@ static uint8_t			ao_adc_done;
 static void ao_adc_dma_done(int index)
 {
 	(void) index;
-	ao_adc_done = 1;
-	ao_wakeup(&ao_adc_done);
+	ao_adc_ring_head += AO_ADC_RING_CHUNK;
+	if (ao_adc_ring_head == AO_ADC_RING_SIZE)
+		ao_adc_ring_head = 0;
+	ao_adc_running = 0;
+	ao_wakeup(&ao_adc_ring_head);
+	ao_dma_done_transfer(STM_DMA_INDEX(STM_DMA_CHANNEL_ADC_1));
 }
 
-/*
- * Start the ADC sequence using the DMA engine
- */
 void
-ao_adc_read(uint16_t *dest, int len)
+_ao_adc_start(void)
 {
-	ao_adc_done = 0;
+	uint16_t	*buf;
+
+	if (ao_adc_running)
+		return;
+	if (_ao_adc_space() < AO_ADC_RING_CHUNK)
+		return;
+	ao_adc_running = 1;
+	buf = ao_adc_ring + ao_adc_ring_head;
 	stm_adc.isr = 0;
 	ao_dma_set_transfer(STM_DMA_INDEX(STM_DMA_CHANNEL_ADC_1),
 			    &stm_adc.dr,
-			    dest,
-			    len,
+			    buf,
+			    AO_ADC_RING_CHUNK,
 			    (0 << STM_DMA_CCR_MEM2MEM) |
 			    (STM_DMA_CCR_PL_HIGH << STM_DMA_CCR_PL) |
 			    (STM_DMA_CCR_MSIZE_16 << STM_DMA_CCR_MSIZE) |
@@ -56,16 +67,6 @@ ao_adc_read(uint16_t *dest, int len)
 	ao_dma_start(STM_DMA_INDEX(STM_DMA_CHANNEL_ADC_1));
 
 	stm_adc.cr |= (1 << STM_ADC_CR_ADSTART);
-	ao_arch_block_interrupts();
-	while (!ao_adc_done)
-		ao_sleep(&ao_adc_done);
-	ao_arch_release_interrupts();
-
-	ao_dma_done_transfer(STM_DMA_INDEX(STM_DMA_CHANNEL_ADC_1));
-
-	stm_adc.cr |= (1 << STM_ADC_CR_ADSTP);
-	while ((stm_adc.cr & (1 << STM_ADC_CR_ADSTP)) != 0)
-		;
 }
 
 void
@@ -185,4 +186,5 @@ ao_adc_init(void)
 	stm_syscfg.cfgr1 &= ~(1 << STM_SYSCFG_CFGR1_ADC_DMA_RMP);
 
 	ao_dma_alloc(STM_DMA_INDEX(STM_DMA_CHANNEL_ADC_1));
+	ao_dma_set_isr(STM_DMA_INDEX(STM_DMA_CHANNEL_ADC_1), ao_adc_dma_done);
 }
diff --git a/src/stmf0/ao_adc_fast.h b/src/stmf0/ao_adc_fast.h
index a2408d14..eec45505 100644
--- a/src/stmf0/ao_adc_fast.h
+++ b/src/stmf0/ao_adc_fast.h
@@ -24,4 +24,66 @@ ao_adc_read(uint16_t *dest, int len);
 void
 ao_adc_init(void);
 
+/* Total ring size in samples */
+#define AO_ADC_RING_SIZE	256
+/* Number of samples fetched per ao_adc_start call */
+#define AO_ADC_RING_CHUNK	(AO_ADC_RING_SIZE >> 1)
+
+extern uint16_t	ao_adc_ring[AO_ADC_RING_SIZE];
+
+#define ao_adc_ring_step(pos,inc)	(((pos) + (inc)) & (AO_ADC_RING_SIZE - 1))
+
+extern uint16_t	ao_adc_ring_head, ao_adc_ring_tail;
+extern uint8_t	ao_adc_running;
+
+void
+_ao_adc_start(void);
+
+static inline uint16_t
+_ao_adc_remain(void)
+{
+	if (ao_adc_ring_tail > ao_adc_ring_head)
+		return AO_ADC_RING_SIZE - ao_adc_ring_tail;
+	return ao_adc_ring_head - ao_adc_ring_tail;
+}
+
+static inline uint16_t
+_ao_adc_space(void)
+{
+	if (ao_adc_ring_head == ao_adc_ring_tail)
+		return AO_ADC_RING_SIZE;
+	if (ao_adc_ring_head > ao_adc_ring_tail)
+		return AO_ADC_RING_SIZE - ao_adc_ring_head;
+	return ao_adc_ring_tail - ao_adc_ring_head;
+}
+
+static inline uint16_t *
+ao_adc_get(uint16_t n)
+{
+	if (ao_adc_ring_tail + n > AO_ADC_RING_SIZE)
+		ao_panic(AO_PANIC_ADC);
+	ao_arch_block_interrupts();
+	while (_ao_adc_remain() < n) {
+		if (!ao_adc_running)
+			_ao_adc_start();
+		ao_sleep(&ao_adc_ring_head);
+	}
+	ao_arch_release_interrupts();
+	return &ao_adc_ring[ao_adc_ring_tail];
+}
+
+static inline void
+ao_adc_ack(uint16_t n)
+{
+	if (ao_adc_ring_tail + n > AO_ADC_RING_SIZE)
+		ao_panic(AO_PANIC_ADC);
+	ao_arch_block_interrupts();
+	ao_adc_ring_tail += n;
+	if (ao_adc_ring_tail == AO_ADC_RING_SIZE)
+		ao_adc_ring_tail = 0;
+	if (!ao_adc_running && _ao_adc_space() >= AO_ADC_RING_CHUNK)
+		_ao_adc_start();
+	ao_arch_release_interrupts();
+}
+
 #endif /* _AO_ADC_FAST_H_ */
diff --git a/src/usbtrng-v2.0/ao_usbtrng.c b/src/usbtrng-v2.0/ao_usbtrng.c
index 26cfbac9..e1f43cdd 100644
--- a/src/usbtrng-v2.0/ao_usbtrng.c
+++ b/src/usbtrng-v2.0/ao_usbtrng.c
@@ -23,7 +23,6 @@ static void
 ao_trng_fetch(void)
 {
 	static uint16_t	*buffer[2];
-	static uint32_t	adc_in[AO_USB_IN_SIZE/2];	/* twice as many as we need */
 	uint32_t	kbytes = 1;
 	uint32_t	count;
 	int		usb_buf_id;
@@ -50,18 +49,21 @@ ao_trng_fetch(void)
 
 	ao_led_on(AO_LED_GREEN);
 	while (count--) {
-		ao_adc_read((uint16_t *) adc_in, AO_USB_IN_SIZE);
-		rnd = adc_in;
 		buf = buffer[usb_buf_id];
+//		printf ("before get: head %3d tail %3d running %d\n", ao_adc_ring_head, ao_adc_ring_tail, ao_adc_running); flush();
+		rnd = (uint32_t *) ao_adc_get(AO_USB_IN_SIZE);	/* one 16-bit value per output byte */
+//		printf ("after get: head %3d tail %3d running %d\n", ao_adc_ring_head, ao_adc_ring_tail, ao_adc_running); flush();
 		for (i = 0; i < 32; i++)
 			*buf++ = ao_crc_in_32_out_16(*rnd++);
+		ao_adc_ack(AO_USB_IN_SIZE);
+//		printf ("after ack: head %3d tail %3d running %d\n", ao_adc_ring_head, ao_adc_ring_tail, ao_adc_running); flush();
 		ao_led_toggle(AO_LED_GREEN|AO_LED_RED);
 		ao_usb_write(buffer[usb_buf_id], AO_USB_IN_SIZE);
 		ao_led_toggle(AO_LED_GREEN|AO_LED_RED);
 		usb_buf_id = 1-usb_buf_id;
 	}
 	ao_led_off(AO_LED_GREEN|AO_LED_RED);
-	ao_usb_flush();
+	flush();
 }
 
 static const struct ao_cmds usbtrng_cmds[] = {