drivers/dma.c

@@ -133,6 +133,20 @@ void dma_disable(enum DmaPeriph dma, enum DmaChannel channel)
 	}
 }
 
+uint16_t dma_get_remaining(enum DmaPeriph dma, enum DmaChannel channel)
+{
+	switch (dma) {
+		case DMA_PERIPH_1:
+			return dma1->CHANNELS[channel].CNDTR.NDT;
+			break;
+		case DMA_PERIPH_2:
+			return dma2->CHANNELS[channel].CNDTR.NDT;
+			break;
+		default:
+			return 0;
+			break;
+	}
+}
 
 //--local functions-------------------------------------------------------------
 

drivers/dma.h

@@ -94,6 +94,8 @@ void dma_enable(enum DmaPeriph dma, enum DmaChannel channel);
 
 void dma_disable(enum DmaPeriph dma, enum DmaChannel channel);
 
+uint16_t dma_get_remaining(enum DmaPeriph dma, enum DmaChannel channe);
+
 
 #endif //_DMA_H_
 

drivers/usart.c

@@ -19,9 +19,12 @@
 
 //--local definitions-----------------------------------------------------------
 
-static volatile struct USART* const usart1 = (struct USART*)USART1_BASE_ADDRESS;
+struct CircularBuffer {
-static volatile struct USART* const usart2 = (struct USART*)USART2_BASE_ADDRESS;
+	volatile uint8_t* buffer;
-static volatile struct USART* const usart3 = (struct USART*)USART3_BASE_ADDRESS;
+	uint16_t size;
+	uint16_t begin;
+	bool dmaLooped;
+};
 
 static void configure_usart(volatile struct USART* regs,
 		enum UsartConfig config);
@@ -29,7 +32,7 @@ static void configure_baudrate(volatile struct USART* regs, uint32_t clock,
 		uint32_t baudrate);
 static uint32_t periph_regs(enum UsartPeriph periph,
 		volatile struct USART** regs);
-static uint32_t read_from_buffer(volatile uint8_t* buffer,
+static uint32_t read_from_buffer(struct CircularBuffer* buffer,
 		enum DmaChannel channel, uint8_t* byte);
 
 static void usart1_rx_callback(enum DmaIRQSource src);
@@ -37,7 +40,11 @@ static void usart1_rx_callback(enum DmaIRQSource src);
 
 //--local variables-------------------------------------------------------------
 
-static volatile uint8_t* usart1_rx_buffer;
+static volatile struct USART* const usart1 = (struct USART*)USART1_BASE_ADDRESS;
+static volatile struct USART* const usart2 = (struct USART*)USART2_BASE_ADDRESS;
+static volatile struct USART* const usart3 = (struct USART*)USART3_BASE_ADDRESS;
+
+static struct CircularBuffer usart1_rx_buffer;
 
 
 //--public functions------------------------------------------------------------
@@ -87,13 +94,13 @@ uint32_t usart_write_byte(enum UsartPeriph periph, uint8_t byte)
 uint32_t usart_read_byte(enum UsartPeriph periph, uint8_t* byte)
 {
 	volatile struct USART* regs;
-	volatile uint8_t* buffer;
+	struct CircularBuffer* buffer;
 	enum DmaChannel dma_channel;
 
 	switch (periph) {
 		case USART_PERIPH_1:
 			regs = usart1;
-			buffer = usart1_rx_buffer;
+			buffer = &usart1_rx_buffer;
 			dma_channel = DMA_CHANNEL_5;
 			break;
 		case USART_PERIPH_2:
@@ -103,7 +110,7 @@ uint32_t usart_read_byte(enum UsartPeriph periph, uint8_t* byte)
 			break;
 	}
 
-	if (buffer) {
+	if (buffer->buffer) {
 		return read_from_buffer(buffer, dma_channel, byte);
 	} else {
 		if (regs->SR.RXNE) {
@@ -126,7 +133,10 @@ void usart_set_rx_buffer(enum UsartPeriph periph, uint8_t* buffer,
 					| DMA_CONFIG_PSIZE_8BITS | DMA_CONFIG_MSIZE_8BITS
 					| DMA_CONFIG_PRIO_LOW, (void*)&usart1->DR, buffer,
 					size, usart1_rx_callback);
-			usart1_rx_buffer = buffer;
+			usart1_rx_buffer.buffer = buffer;
+			usart1_rx_buffer.size = size;
+			usart1_rx_buffer.begin = 0;
+			usart1_rx_buffer.dmaLooped = false;
 			reg_set(usart1->CR3, USART_CR3_DMAR);
 			break;
 		case USART_PERIPH_2:
@@ -140,6 +150,7 @@ void usart_set_rx_buffer(enum UsartPeriph periph, uint8_t* buffer,
 
 static void configure_usart(volatile struct USART* regs, enum UsartConfig config)
 {
+	usart1_rx_buffer.buffer = NULL;
 	//configure parity
 	switch (config)
 	{
@@ -247,16 +258,34 @@ static uint32_t periph_regs(enum UsartPeriph periph, volatile struct USART** reg
 	return 0;
 }
 
-static uint32_t read_from_buffer(volatile uint8_t* buffer,
+static uint32_t read_from_buffer(struct CircularBuffer* buffer,
 		enum DmaChannel channel, uint8_t* byte)
 {
+	uint16_t end = buffer->size - dma_get_remaining(DMA_PERIPH_1, channel);
 
+	if ((end > buffer->begin) && buffer->dmaLooped) {
+		//TODO overflow
+		buffer->begin = end;
+	} else if ((buffer->begin == end) && !buffer->dmaLooped) {
+		//TODO no data
+		return 1;
+	}
+
+	*byte = buffer->buffer[buffer->begin];
+	++buffer->begin;
+	if (buffer->begin >= buffer->size) {
+		buffer->begin = 0;
+		buffer->dmaLooped = false;
+	}
+
+	return 0;
 }
 
 //--callbacks-------------------------------------------------------------------
 
 static void usart1_rx_callback(enum DmaIRQSource src)
 {
-
+	(void)src; //only transfer complete expected
+	usart1_rx_buffer.dmaLooped = true;
 }