diff options
Diffstat (limited to 'examples/test-usart-dma.cpp')
| -rw-r--r-- | examples/test-usart-dma.cpp | 211 |
1 files changed, 0 insertions, 211 deletions
diff --git a/examples/test-usart-dma.cpp b/examples/test-usart-dma.cpp deleted file mode 100644 index d10dc68..0000000 --- a/examples/test-usart-dma.cpp +++ /dev/null @@ -1,211 +0,0 @@ -/** - * @file examples/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 sending characters after filling the buffer, you'll - * overwrite earlier bytes; this may happen before those earlier bytes - * are done printing. (Typing quickly and seeing how it affects the - * output is a fun way to make sense of how the interrupts and the - * main thread of execution interleave.) - * - * This code is released into the public domain. - */ - -#include <libmaple/dma.h> -#include <libmaple/usart.h> -#include <libmaple/gpio.h> - -#include <wirish/wirish.h> - -/* - * Configuration and state - */ - -// Serial port and DMA configuration. You can change these to suit -// your purposes. -HardwareSerial *serial = &Serial2; -#define USART_DMA_DEV DMA1 -#if STM32_MCU_SERIES == STM32_SERIES_F1 -// On STM32F1 microcontrollers (like what's on Maple and Maple Mini), -// dma tubes are channels. -#define USART_RX_DMA_TUBE DMA_CH6 -#elif (STM32_MCU_SERIES == STM32_SERIES_F2 || \ - STM32_MCU_SERIES == STM32_SERIES_F4) -// On STM32F2 and STM32F4 microcontrollers (Maple 2 will have an F4), -// dma tubes are streams. -#define USART_RX_DMA_TUBE DMA_S5 -#else -#error "unsupported stm32 series" -#endif -// The serial port will make a DMA request each time it receives data. -// This is the dma_request_src we use to tell the DMA tube to handle -// that DMA request. -#define USART_DMA_REQ_SRC DMA_REQ_SRC_USART2_RX -#define BAUD 9600 - -// This will store the DMA configuration for USART RX. -dma_tube_config tube_config; - -// This will store received USART characters. -#define BUF_SIZE 20 -char rx_buf[BUF_SIZE]; - -// The interrupt handler, rx_dma_irq(), sets this to 1. -volatile uint32 irq_fired = 0; -// 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; - -/* - * Helper functions - */ - -// This is our DMA interrupt handler. -void rx_dma_irq(void) { - irq_fired = 1; - isr = dma_get_isr_bits(USART_DMA_DEV, USART_RX_DMA_TUBE); -} - -// 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 setup_usart(void) { - serial->begin(BAUD); - usart_dev *serial_dev = serial->c_dev(); - serial_dev->regs->CR3 = USART_CR3_DMAR; -} - -// Set up our dma_tube_config structure. (We could have done this -// above, when we declared tube_config, but having this function makes -// it easier to explain what's going on). -void setup_tube_config(void) { - // We're receiving from the USART data register. serial->c_dev() - // returns a pointer to the libmaple usart_dev for that serial - // port, so this is a pointer to its data register. - tube_config.tube_src = &serial->c_dev()->regs->DR; - // We're only interested in the bottom 8 bits of that data register. - tube_config.tube_src_size = DMA_SIZE_8BITS; - // We're storing to rx_buf. - tube_config.tube_dst = rx_buf; - // rx_buf is a char array, and a "char" takes up 8 bits on STM32. - tube_config.tube_dst_size = DMA_SIZE_8BITS; - // Only fill BUF_SIZE - 1 characters, to leave a null byte at the end. - tube_config.tube_nr_xfers = BUF_SIZE - 1; - // Flags: - // - DMA_CFG_DST_INC so we start at the beginning of rx_buf and - // fill towards the end. - // - DMA_CFG_CIRC so we go back to the beginning and start over when - // rx_buf fills up. - // - DMA_CFG_CMPLT_IE to turn on interrupts on transfer completion. - tube_config.tube_flags = DMA_CFG_DST_INC | DMA_CFG_CIRC | DMA_CFG_CMPLT_IE; - // Target data: none. It's important to set this to NULL if you - // don't have any special (microcontroller-specific) configuration - // in mind, which we don't. - tube_config.target_data = NULL; - // DMA request source. - tube_config.tube_req_src = USART_DMA_REQ_SRC; -} - -// Configure the DMA controller to serve DMA requests from the USART. -void setup_dma_xfer(void) { - // First, turn it on. - dma_init(USART_DMA_DEV); - // Next, configure it by calling dma_tube_cfg(), and check to make - // sure it succeeded. DMA tubes have many restrictions on their - // configuration, and there are configurations which work on some - // types of STM32 but not others. libmaple tries hard to make - // things just work, but checking the return status is important! - int status = dma_tube_cfg(USART_DMA_DEV, USART_RX_DMA_TUBE, &tube_config); - ASSERT(status == DMA_TUBE_CFG_SUCCESS); - // Now we'll perform any other configuration we want. For this - // example, we attach an interrupt handler. - dma_attach_interrupt(USART_DMA_DEV, USART_RX_DMA_TUBE, rx_dma_irq); - // Turn on the DMA tube. It will now begin serving requests. - dma_enable(USART_DMA_DEV, USART_RX_DMA_TUBE); -} - -/* - * setup() and loop() - */ - -void setup(void) { - pinMode(BOARD_LED_PIN, OUTPUT); - setup_tube_config(); - setup_dma_xfer(); - setup_usart(); -} - -void loop(void) { - toggleLED(); - delay(100); - - // See if the interrupt handler got called since the last time we - // checked. - if (irq_fired) { - serial->println("** IRQ **"); - // 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 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 - // don't tell the DMA controller to interrupt us on a - // half-complete transfer. That is, the ISR bits get set at the - // right times no matter what; we just don't get interrupted - // unless we asked. (If an error or other problem occurs, the - // relevant ISR bits will get set in the same way). - serial->print("["); - serial->print(millis()); - serial->print("]\tISR bits: 0x"); - uint8 isr_bits = dma_get_isr_bits(USART_DMA_DEV, USART_RX_DMA_TUBE); - serial->print(isr_bits, HEX); - - // Print the contents of rx_buf. If you keep typing after it fills - // up, the new characters will overwrite the old ones, thanks to - // DMA_CIRC_MODE. - serial->print("\tCharacter buffer contents: '"); - serial->print(rx_buf); - serial->println("'"); - if (isr_bits == 0x7) { - serial->println("** Clearing ISR bits."); - dma_clear_isr_bits(USART_DMA_DEV, USART_RX_DMA_TUBE); - } -} - -// ------- init() and main() -------------------------------------------------- - -// 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; -} |