136 lines
4.5 KiB
C
136 lines
4.5 KiB
C
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/** \file
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\brief Serial subsystem, ARM specific part.
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To be included from serial.c, for more details see there.
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Other than AVRs, ARMs feature a serial buffer in hardware, so we can get
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away without a software buffer and also without(!) interrupts.
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Code here is heavily inspired by serial_api.c of MBED
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*/
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#if defined TEACUP_C_INCLUDE && defined __ARM_STM32F411__
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#include "arduino.h"
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#ifdef XONXOFF
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#error XON/XOFF protocol not yet implemented for ARM. \
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See serial-avr.c for inspiration.
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#endif
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USART_TypeDef *port = USART2;
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void serial_init()
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{
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// Enable TX/RX clock (GPIOA)
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RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN;
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// Enable USART2 clock
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RCC->APB1ENR |= RCC_APB1ENR_USART2EN;
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// Configure the UART pins
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// AF 4bits per channel
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// Alternate functions from DM00115249.pdf datasheet (page 47; table 9)
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TXD_PORT->AFR[0] |= (((uint8_t)0x07) << ((TXD_PIN) << 2));
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RXD_PORT->AFR[0] |= (((uint8_t)0x07) << ((RXD_PIN) << 2));
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// MODER 2bits per channel
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TXD_PORT->MODER |= (GPIO_MODE_AF_PP << ((TXD_PIN) << 1)); // set bit2: alternate function
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RXD_PORT->MODER |= (GPIO_MODE_AF_PP << ((RXD_PIN) << 1));
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TXD_PORT->OSPEEDR |= GPIO_SPEED_HIGH << ((TXD_PIN) << 1);
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RXD_PORT->OSPEEDR |= GPIO_SPEED_HIGH << ((RXD_PIN) << 1);
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TXD_PORT->PUPDR |= (GPIO_PULLUP << ((TXD_PIN) << 1)); //Pullup
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RXD_PORT->PUPDR |= (GPIO_PULLUP << ((RXD_PIN) << 1)); //Pullup? LPC has No Pull-up or Pull-down activation
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/* Disable the peripheral */
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port->CR1 &= ~USART_CR1_UE;
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/* Set the UART Communication parameters */
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/*-------------------------- USART CR2 Configuration -----------------------*/
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/* Clear STOP[13:12] bits */
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port->CR2 &= ~(USART_CR2_STOP);
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/* Configure the UART Stop Bits: Set STOP[13:12] bits according to huart->Init.StopBits value */
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port->CR2 |= UART_STOPBITS_1;
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/*-------------------------- USART CR1 Configuration -----------------------*/
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/* Clear M, PCE, PS, TE and RE bits */
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port->CR1 &= ~(USART_CR1_M | USART_CR1_PCE | USART_CR1_PS | USART_CR1_TE | \
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USART_CR1_RE | USART_CR1_OVER8);
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/* Configure the UART Word Length, Parity and mode:
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Set the M bits according to huart->Init.WordLength value
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Set PCE and PS bits according to huart->Init.Parity value
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Set TE and RE bits according to huart->Init.Mode value
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Set OVER8 bit according to huart->Init.OverSampling value */
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port->CR1 |= UART_WORDLENGTH_8B | UART_PARITY_NONE | UART_MODE_TX_RX | UART_OVERSAMPLING_16;
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/*-------------------------- USART CR3 Configuration -----------------------*/
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/* Clear CTSE and RTSE bits */
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port->CR3 &= ~(USART_CR3_RTSE | USART_CR3_CTSE);
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/* Configure the UART HFC: Set CTSE and RTSE bits according to huart->Init.HwFlowCtl value */
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port->CR3 |= UART_HWCONTROL_NONE;
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/* 19.3.4 Fractional baud rate generation => reference manual for STM32F411
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Set BRR for 115,200 Hz
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div = 48MHz/(16*BAUD)
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Mantisse = int(div) << 8
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Divisor = int((div - int(div))*16)
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BRR = Mantisse + Divisor
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*/
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#define BAUD 115200
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#define SERIAL_APBCLK (__SYSTEM_CLOCK/2)
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#define INT_DIVIDER ((25 * SERIAL_APBCLK) / (4 * BAUD))
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#define BAUD_H ((INT_DIVIDER / 100) << 4)
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#define FRACT_DIVIDER (INT_DIVIDER - (100 * (BAUD_H >> 4)))
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#define BAUD_L (((((FRACT_DIVIDER * 16) + 50) / 100)) & 0X0F)
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port->BRR = BAUD_H | BAUD_L;
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/* In asynchronous mode, the following bits must be kept cleared:
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- LINEN and CLKEN bits in the USART_CR2 register,
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- SCEN, HDSEL and IREN bits in the USART_CR3 register.*/
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port->CR2 &= ~(USART_CR2_LINEN | USART_CR2_CLKEN);
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port->CR3 &= ~(USART_CR3_SCEN | USART_CR3_HDSEL | USART_CR3_IREN);
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/* Enable the peripheral */
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port->CR1 |= USART_CR1_UE;
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}
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/** Check wether characters can be read.
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Other than the AVR implementation this returns not the number of characters
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in the line, but only wether there is at least one or not.
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*/
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uint8_t serial_rxchars(void) {
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return port->SR & UART_FLAG_RXNE;
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}
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/** Read one character.
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*/
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uint8_t serial_popchar(void) {
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uint8_t c = 0;
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if (serial_rxchars())
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c = (uint8_t)(port->DR & 0x1FF);
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return c;
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}
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/** Check wether characters can be written
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*/
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uint8_t serial_txchars(void) {
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return port->SR &UART_FLAG_TXE;
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}
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/** Send one character.
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*/
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void serial_writechar(uint8_t data) {
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while (!serial_txchars());
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port->DR = (uint32_t)(data & 0x1FF);
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}
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#endif /* defined TEACUP_C_INCLUDE && defined __ARM_STM32F411__ */ |