Configure the DMA channels in circular mode so that we don't have to deal with the case where DMA stops but the master is still talking.

Use AF as well as STOPF to decide when transfer has ended. We don't seem to get STOPF when we are transmitting.

apps/px4io/i2c.c

@@ -69,8 +69,8 @@ static void		i2c_dump(void);
 
 static void		i2c_rx_setup(void);
 static void		i2c_tx_setup(void);
-static void		i2c_rx_complete(DMA_HANDLE handle, uint8_t status, void *arg);
-static void		i2c_tx_complete(DMA_HANDLE handle, uint8_t status, void *arg);
+static void		i2c_rx_complete(void);
+static void		i2c_tx_complete(void);
 
 static DMA_HANDLE	rx_dma;
 static DMA_HANDLE	tx_dma;
@@ -111,7 +111,7 @@ i2c_init(void)
 	rCR1 = 0;
 
 	/* set for DMA operation */
-	rCR2 |= I2C_CR2_ITEVFEN | I2C_CR2_DMAEN;
+	rCR2 |= I2C_CR2_ITEVFEN |I2C_CR2_ITERREN | I2C_CR2_DMAEN;
 
 	/* set the frequency value in CR2 */
 	rCR2 &= ~I2C_CR2_FREQ_MASK;
@@ -131,7 +131,9 @@ i2c_init(void)
 
 	/* enable event interrupts */
 	irq_attach(STM32_IRQ_I2C1EV, i2c_interrupt);
+	irq_attach(STM32_IRQ_I2C1ER, i2c_interrupt);
 	up_enable_irq(STM32_IRQ_I2C1EV);
+	up_enable_irq(STM32_IRQ_I2C1ER);
 
 	/* and enable the I2C port */
 	rCR1 |= I2C_CR1_ACK | I2C_CR1_PE;
@@ -154,30 +156,31 @@ i2c_interrupt(int irq, FAR void *context)
 			/* we are the transmitter */
 
 			direction = DIR_TX;
-			stm32_dmastart(tx_dma, i2c_tx_complete, NULL, false);
+			stm32_dmastart(tx_dma, NULL, NULL, false);
 
 		} else {
 			/* we are the receiver */
 
 			direction = DIR_RX;
-			stm32_dmastart(rx_dma, i2c_rx_complete, NULL, false);			
+			stm32_dmastart(rx_dma, NULL, NULL, false);			
 		}
 	}
 
-	if (sr1 & I2C_SR1_STOPF) {
-		/* write to CR1 to clear STOPF */
-		(void)rSR1;		/* as recommended, re-read SR1 */
-		rCR1 |= I2C_CR1_PE;
+	if (sr1 & (I2C_SR1_STOPF | I2C_SR1_AF)) {
+
+		if (sr1 & I2C_SR1_STOPF) {
+			/* write to CR1 to clear STOPF */
+			(void)rSR1;		/* as recommended, re-read SR1 */
+			rCR1 |= I2C_CR1_PE;
+		}
 
 		/* it's likely that the DMA hasn't stopped, so we have to do it here */
 		switch (direction) {
 		case DIR_TX:
-			stm32_dmastop(tx_dma);
-			i2c_tx_complete(tx_dma, 0, NULL);
+			i2c_tx_complete();
 			break;
 		case DIR_RX:
-			stm32_dmastop(rx_dma);
-			i2c_rx_complete(rx_dma, 0, NULL);
+			i2c_rx_complete();
 			break;
 		default:
 			/* spurious stop, ignore */
@@ -186,7 +189,7 @@ i2c_interrupt(int irq, FAR void *context)
 		direction = DIR_NONE;
 	}
 
-	/* clear any errors that might need it */
+	/* clear any errors that might need it (this handles AF as well */
 	if (sr1 & I2C_SR1_ERRORMASK)
 		rSR1 = 0;
 
@@ -196,8 +199,14 @@ i2c_interrupt(int irq, FAR void *context)
 static void
 i2c_rx_setup(void)
 {
+	/*
+	 * Note that we configure DMA in circular mode; this means that a too-long
+	 * transfer will overwrite the buffer, but that avoids us having to deal with
+	 * bailing out of a transaction while the master is still babbling at us.
+	 */
 	rx_len = 0;
 	stm32_dmasetup(rx_dma, (uintptr_t)&rDR, (uintptr_t)&rx_buf[0], sizeof(rx_buf),
+		DMA_CCR_CIRC |
 		DMA_CCR_MINC |
 		DMA_CCR_PSIZE_32BITS |
 		DMA_CCR_MSIZE_8BITS |
@@ -205,22 +214,33 @@ i2c_rx_setup(void)
 }
 
 static void
-i2c_rx_complete(DMA_HANDLE handle, uint8_t status, void *arg)
+i2c_rx_complete(void)
 {
 	rx_len = sizeof(rx_buf) - stm32_dmaresidual(rx_dma);
+	stm32_dmastop(rx_dma);
 
-	for (unsigned i = 0; i < rx_len; i++)
+	/* XXX handle reception */
+	for (unsigned i = 0; i < rx_len; i++) {
 		tx_buf[i] = rx_buf[i] + 1;
+		rx_buf[i] = 0;
+	}
 
-	/* XXX handle reception */
+	/* prepare for the next transaction */
 	i2c_rx_setup();
 }
 
 static void
 i2c_tx_setup(void)
 {
+	/*
+	 * Note that we configure DMA in circular mode; this means that a too-long
+	 * transfer will copy the buffer more than once, but that avoids us having
+	 * to deal with bailing out of a transaction while the master is still 
+	 * babbling at us.
+	 */
 	stm32_dmasetup(tx_dma, (uintptr_t)&rDR, (uintptr_t)&tx_buf[0], sizeof(tx_buf),
 		DMA_CCR_DIR |
+		DMA_CCR_CIRC |
 		DMA_CCR_MINC |
 		DMA_CCR_PSIZE_8BITS |
 		DMA_CCR_MSIZE_8BITS |
@@ -228,9 +248,14 @@ i2c_tx_setup(void)
 }
 
 static void
-i2c_tx_complete(DMA_HANDLE handle, uint8_t status, void *arg)
+i2c_tx_complete(void)
 {
+	stm32_dmastop(tx_dma);
+
 	/* XXX handle transmit-done */
+
+	/* prepare for the next transaction */
+	memset(tx_buf, 0, sizeof(tx_buf));
 	i2c_tx_setup();
 }