uart.c

/***********************************************************************************
 * @file        uart.c                                                             *
 * @author      Matt Ricci                                                         *
 * @addtogroup  UART                                                               *
 * @brief       Brief description of the file's purpose.                           *
 *                                                                                 *
 * @todo Implement printf                                                          *
 ***********************************************************************************/
 
#include "uart.h"
#include "stddef.h"
#include "config.h"
 
static void _UART_init(UART_t *uart, uint32_t baud, UART_Config *config);
 
/* =============================================================================== */
UART_t UART_init(USART_TypeDef *interface, uint32_t baud, UART_Config *config) {
  // Early return error struct if peripheral is NULL
  if (interface == NULL)
    return (UART_t){.interface = NULL};
 
  // Initialise uart struct with interface
  UART_t uart    = {.interface = interface};
 
  uart.setBaud   = UART_setBaud;
  uart.send      = UART_send;
  uart.sendBytes = UART_sendBytes;
  uart.print     = UART_print;
  uart.println   = UART_println;
  uart.receive   = UART_receive;
  uart.interface = interface;
  uart.baud      = baud;
 
  // Update config and enable peripheral
  UART_updateConfig(&uart, config);
 
  return uart;
}
 
// ALLOW FORMATTING
#ifndef __DOXYGEN__
 
/* =============================================================================== */
static void _UART_init(UART_t *uart, uint32_t baud, UART_Config *config) {
  USART_TypeDef *interface = uart->interface;
 
  // Disable peripheral and update config
  config->UE      = false;                                    // Make sure UE is disabled in config
  interface->CR1 &= *(uint16_t *)config & ~UART_CR1_RESERVED; // Update CR1 with configured values
  interface->CR1 |= *(uint16_t *)config & ~UART_CR1_RESERVED; // Update CR1 with configured values
 
  // Update baud rate
  UART_setBaud(uart, baud);
}
 
#endif
 
/********************************** INTERFACE METHODS ********************************/
 
void UART_setBaud(UART_t *uart, uint32_t baud) {
  USART_TypeDef *interface = uart->interface;
 
  // Wait for interface to be freed
  while ((interface->SR & USART_SR_TXE) == 0 && !(interface->SR & USART_SR_TC));
  interface->CR1 &= ~USART_CR1_UE;
  while ((interface->SR & USART_SR_RXNE) == 1) {
    (void)(interface->DR & 0xFF);
  }
 
  // Calculate relevant APBx clock for peripheral
  uint32_t sysclk = HSE_USED ? SYSCLK_HSE : SYSCLK_HSI;
  uint8_t hpre    = AHBPresc[((RCC->CFGR & RCC_CFGR_HPRE) >> RCC_CFGR_HPRE_Pos)];
 
  uint8_t ppre;
  // Set prescale value according to peripheral bus
  if (interface == USART1 || interface == USART6) {
    ppre = APBPresc[((RCC->CFGR & RCC_CFGR_PPRE2) >> RCC_CFGR_PPRE2_Pos)];
  } else {
    ppre = APBPresc[((RCC->CFGR & RCC_CFGR_PPRE1) >> RCC_CFGR_PPRE1_Pos)];
  }
 
  // Calculate peripheral bus clock from prescalers
  uint32_t pclk     = sysclk / hpre / ppre;
 
  uint16_t usartDiv = ((pclk / baud) * (1 + uart->config.OVER8));
  if (uart->config.OVER8 && (usartDiv & 0x08)) {
    usartDiv &= ~0x0F;
    usartDiv |= 0x07;
  }
  interface->BRR &= 0xFFFF0000; // Clear mantissa and div in baud rate reg
  interface->BRR |= usartDiv;   // Set baud rate
 
  interface->CR1 |= USART_CR1_UE;
}
 
/* =============================================================================== */
void UART_send(UART_t *uart, uint8_t data) {
  USART_TypeDef *interface = uart->interface;
  while ((interface->SR & USART_SR_TXE) == 0);
  interface->DR = data;
  while ((interface->SR & USART_SR_TC) == 0);
}
 
/* =============================================================================== */
void UART_sendBytes(UART_t *uart, uint8_t *data, int length) {
  for (int i = 0; i < length; i++)
    UART_send(uart, data[i]);
}
 
/* =============================================================================== */
 
void UART_print(UART_t *uart, char *data) {
  int i = 0;
  while (data[i] != '\0')
    UART_send(uart, data[i++]);
}
 
/* =============================================================================== */
 
void UART_println(UART_t *uart, char *data) {
  UART_print(uart, data);
  UART_print(uart, "\r\n");
}
 
/* =============================================================================== */
uint8_t UART_receive(UART_t *uart) {
  USART_TypeDef *interface = uart->interface;
  while ((interface->SR & USART_SR_RXNE) == 0);
  return (uint8_t)(interface->DR & 0xFF);
}
 
/* =============================================================================== */
void UART_updateConfig(UART_t *uart, UART_Config *config) {
  // Initialise config with default values if passed NULL.
  if (config == NULL) {
    config = &UART_CONFIG_DEFAULT;
  }
 
  // Update peripheral with new config
  uart->config = *config;
 
  // Initialise SPI registers and enable peripheral
  _UART_init(uart, uart->baud, config);
}