diff options
| -rw-r--r-- | examples/test-usart-dma.cpp | 33 |
1 files changed, 17 insertions, 16 deletions
diff --git a/examples/test-usart-dma.cpp b/examples/test-usart-dma.cpp index b3c766e..4a63044 100644 --- a/examples/test-usart-dma.cpp +++ b/examples/test-usart-dma.cpp @@ -29,8 +29,8 @@ * Configuration and state */ -// USART and DMA configuration. You can change these to suit your -// purposes. +// Serial port and DMA configuration. You can change these to suit +// your purposes. HardwareSerial *serial = &Serial2; #define USART_DMA_DEV DMA1 #define USART_RX_DMA_CHANNEL DMA_CH6 @@ -42,8 +42,9 @@ char rx_buf[BUF_SIZE]; // The interrupt handler, rx_dma_irq(), sets this to 1. volatile uint32 irq_fired = 0; -// Used to store the ISR bits inside rx_dma_irq(). This helps explain -// what's going on inside loop(); see comments below. +// Used to store DMA interrupt status register (ISR) bits inside +// rx_dma_irq(). This helps explain what's going on inside loop(); see +// comments below. volatile uint32 isr = 0; /* @@ -59,14 +60,14 @@ void rx_dma_irq(void) { // Configure the USART receiver for use with DMA: // 1. Turn it on. // 2. Set the "DMA request on RX" bit in USART_CR3 (USART_CR3_DMAR). -void init_usart(void) { +void setup_usart(void) { serial->begin(BAUD); usart_dev *serial_dev = serial->c_dev(); serial_dev->regs->CR3 = USART_CR3_DMAR; } // Configure the DMA controller to serve DMA requests from the USART. -void init_dma_xfer(void) { +void setup_dma_xfer(void) { dma_init(USART_DMA_DEV); dma_setup_transfer(USART_DMA_DEV, USART_RX_DMA_CHANNEL, &serial->c_dev()->regs->DR, DMA_SIZE_8BITS, @@ -84,9 +85,8 @@ void init_dma_xfer(void) { void setup(void) { pinMode(BOARD_LED_PIN, OUTPUT); - rx_buf[BUF_SIZE - 1] = '\0'; // null-terminate rx_buf so we can print it - init_dma_xfer(); - init_usart(); + setup_dma_xfer(); + setup_usart(); } void loop(void) { @@ -97,18 +97,19 @@ void loop(void) { // checked. if (irq_fired) { serial->println("** IRQ **"); - // Notice how the ISR bits show transfer complete _and_ - // half-complete here, but the ISR bits we print next will be - // zero. That's because the variable "isr" gets set _inside_ - // rx_dma_irq(). After it exits, libmaple cleans up by - // clearing the ISR bits. (If it didn't, and we forgot to, the - // interrupt would repeatedly fire forever.) + // Notice how the interrupt status register (ISR) bits show + // transfer complete _and_ half-complete here, but the ISR + // bits we print next will be zero. That's because the + // variable "isr" gets set _inside_ rx_dma_irq(). After it + // exits, libmaple cleans up by clearing the tube's ISR + // bits. (If it didn't, and we forgot to, the interrupt would + // repeatedly fire forever.) serial->print("ISR bits: 0x"); serial->println(isr, HEX); irq_fired = 0; } - // Print the ISR (interrupt status register) bits. + // Print the ISR bits. // // Notice that the "transfer half-complete" ISR flag gets set when // we reach the rx_buf half-way point. This is true even though we |