altos/stmf0: Fix fast ADC interface

This was configuring the hardware wrong, and wasn't keeping the output
ring full.

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

2 files changed, 23 insertions, 18 deletions

diff --git a/src/stmf0/ao_adc_fast.c b/src/stmf0/ao_adc_fast.c
index be9b5986..7d2a4fd7 100644
--- a/src/stmf0/ao_adc_fast.c
+++ b/src/stmf0/ao_adc_fast.c
@@ -18,43 +18,52 @@
 #include <ao.h>
 #include <ao_adc_fast.h>
 
-uint16_t ao_adc_ring[AO_ADC_RING_SIZE];
+uint16_t ao_adc_ring[AO_ADC_RING_SIZE] __attribute__((aligned(4)));
+
+/* Maximum number of samples fetched per _ao_adc_start call */
+#define AO_ADC_RING_CHUNK	(AO_ADC_RING_SIZE >> 1)
 
 uint16_t ao_adc_ring_head, ao_adc_ring_tail;
-uint8_t ao_adc_running;
+uint16_t ao_adc_running;
 
 /*
  * Callback from DMA ISR
  *
- * Mark time in ring, shut down DMA engine
+ * Wakeup any waiting processes, mark the DMA as done, start the ADC
+ * if there's still lots of space in the ring
  */
 static void ao_adc_dma_done(int index)
 {
 	(void) index;
-	ao_adc_ring_head += AO_ADC_RING_CHUNK;
+	ao_adc_ring_head += ao_adc_running;
 	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));
+	_ao_adc_start();
 }
 
 void
 _ao_adc_start(void)
 {
 	uint16_t	*buf;
+	uint16_t	count;
 
 	if (ao_adc_running)
 		return;
-	if (_ao_adc_space() < AO_ADC_RING_CHUNK)
+	count = _ao_adc_space();
+	if (count == 0)
 		return;
-	ao_adc_running = 1;
+	if (count > AO_ADC_RING_CHUNK)
+		count = AO_ADC_RING_CHUNK;
+	ao_adc_running = count;
 	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,
 			    buf,
-			    AO_ADC_RING_CHUNK,
+			    count,
 			    (0 << STM_DMA_CCR_MEM2MEM) |
 			    (STM_DMA_CCR_PL_HIGH << STM_DMA_CCR_PL) |
 			    (STM_DMA_CCR_MSIZE_16 << STM_DMA_CCR_MSIZE) |
@@ -140,7 +149,6 @@ ao_adc_init(void)
 #if AO_NUM_ADC > 8
 #error Need more ADC defines
 #endif
-	stm_adc.chselr = chselr;
 
 	/* Set the clock */
 	stm_adc.cfgr2 = STM_ADC_CFGR2_CKMODE_PCLK_2 << STM_ADC_CFGR2_CKMODE;
@@ -160,14 +168,16 @@ ao_adc_init(void)
 	while ((stm_adc.isr & (1 << STM_ADC_ISR_ADRDY)) == 0)
 		;
 
+	stm_adc.chselr = chselr;
+
 	stm_adc.cfgr1 = ((0 << STM_ADC_CFGR1_AWDCH) |
 			 (0 << STM_ADC_CFGR1_AWDEN) |
 			 (0 << STM_ADC_CFGR1_AWDSGL) |
 			 (0 << STM_ADC_CFGR1_DISCEN) |
 			 (0 << STM_ADC_CFGR1_AUTOOFF) |
-			 (1 << STM_ADC_CFGR1_WAIT) |
+			 (0 << STM_ADC_CFGR1_WAIT) |
 			 (1 << STM_ADC_CFGR1_CONT) |
-			 (0 << STM_ADC_CFGR1_OVRMOD) |
+			 (1 << STM_ADC_CFGR1_OVRMOD) |
 			 (STM_ADC_CFGR1_EXTEN_DISABLE << STM_ADC_CFGR1_EXTEN) |
 			 (0 << STM_ADC_CFGR1_ALIGN) |
 			 (STM_ADC_CFGR1_RES_12 << STM_ADC_CFGR1_RES) |
@@ -186,5 +196,4 @@ 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 eec45505..ca5f7fb9 100644
--- a/src/stmf0/ao_adc_fast.h
+++ b/src/stmf0/ao_adc_fast.h
@@ -26,15 +26,13 @@ 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;
+extern uint16_t	ao_adc_running;
 
 void
 _ao_adc_start(void);
@@ -50,9 +48,7 @@ _ao_adc_remain(void)
 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)
+	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;
 }
@@ -81,7 +77,7 @@ ao_adc_ack(uint16_t n)
 	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)
+	if (!ao_adc_running)
 		_ao_adc_start();
 	ao_arch_release_interrupts();
 }