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/**
* @file test-usart-dma.cpp
* @author Marti Bolivar <mbolivar@leaflabs.com>
*
* Simple test of DMA used with a USART receiver.
*
* Configures a USART receiver for use with DMA. Received bytes are
* placed into a buffer, with an interrupt firing when the buffer is
* full. At that point, the USART transmitter will print the contents
* of the byte buffer. The buffer is continually filled and refilled
* in this manner.
*
* This example isn't very robust; don't use it in production. In
* particular, since the buffer keeps filling (DMA_CIRC_MODE is set),
* if you keep typing after filling the buffer, you'll overwrite
* earlier bytes; this may happen before those earlier bytes are done
* printing.
*
* This code is released into the public domain.
*/
#include "dma.h"
#include "usart.h"
#include "gpio.h"
#include "wirish.h"
#define BAUD 9600
#define USART USART2
#define USART_HWSER Serial2
#define USART_DMA_DEV DMA1
#define USART_RX_DMA_CHANNEL DMA_CH6
#define USART_TX BOARD_USART2_TX_PIN
#define USART_RX BOARD_USART2_RX_PIN
#define BUF_SIZE 8
uint8 rx_buf[BUF_SIZE];
dma_irq_cause irq_cause;
volatile uint32 irq_fired = 0;
void init_usart(void);
void init_dma_xfer(void);
void rx_dma_irq(void);
void setup(void) {
pinMode(BOARD_LED_PIN, OUTPUT);
init_dma_xfer();
init_usart();
}
void loop(void) {
toggleLED();
delay(100);
dma_channel_reg_map *ch_regs = dma_channel_regs(USART_DMA_DEV,
USART_RX_DMA_CHANNEL);
if (irq_fired) {
USART_HWSER.println("** IRQ **");
irq_fired = 0;
}
USART_HWSER.print("[");
USART_HWSER.print(millis());
USART_HWSER.print("]\tISR bits: 0x");
uint8 isr_bits = dma_get_isr_bits(USART_DMA_DEV, USART_RX_DMA_CHANNEL);
USART_HWSER.print(isr_bits, HEX);
USART_HWSER.print("\tCCR: 0x");
USART_HWSER.print(ch_regs->CCR, HEX);
USART_HWSER.print("\tCNDTR: 0x");
USART_HWSER.print(ch_regs->CNDTR, HEX);
USART_HWSER.print("\tBuffer contents: ");
for (int i = 0; i < BUF_SIZE; i++) {
USART_HWSER.print('\'');
USART_HWSER.print(rx_buf[i]);
USART_HWSER.print('\'');
if (i < BUF_SIZE - 1) USART_HWSER.print(", ");
}
USART_HWSER.println();
if (isr_bits == 0x7) {
USART_HWSER.println("** Clearing ISR bits.");
dma_clear_isr_bits(USART_DMA_DEV, USART_RX_DMA_CHANNEL);
}
}
/* Configure USART receiver for use with DMA */
void init_usart(void) {
USART_HWSER.begin(BAUD);
USART->regs->CR3 = USART_CR3_DMAR;
}
/* Configure DMA transmission */
void init_dma_xfer(void) {
dma_init(USART_DMA_DEV);
dma_setup_transfer(USART_DMA_DEV, USART_RX_DMA_CHANNEL,
&USART->regs->DR, DMA_SIZE_8BITS,
rx_buf, DMA_SIZE_8BITS,
(DMA_MINC_MODE | DMA_CIRC_MODE | DMA_TRNS_CMPLT));
dma_set_num_transfers(USART_DMA_DEV, USART_RX_DMA_CHANNEL, BUF_SIZE);
dma_attach_interrupt(USART_DMA_DEV, USART_RX_DMA_CHANNEL, rx_dma_irq);
dma_enable(USART_DMA_DEV, USART_RX_DMA_CHANNEL);
}
void rx_dma_irq(void) {
irq_fired = true;
}
// Force init to be called *first*, i.e. before static object allocation.
// Otherwise, statically allocated objects that need libmaple may fail.
__attribute__((constructor)) void premain() {
init();
}
int main(void) {
setup();
while (true) {
loop();
}
return 0;
}
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