mirror of
https://github.com/eddyem/stm32samples.git
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77 lines
2.4 KiB
C
77 lines
2.4 KiB
C
/*
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* This file is part of the usbcangpio project.
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* Copyright 2026 Edward V. Emelianov <edward.emelianoff@gmail.com>.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <stm32f0.h>
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#include "hardware.h"
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#include "spi.h"
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// get best prescaler to fit given frequency
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static uint16_t get_baudrate_prescaler(uint32_t speed_hz){
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uint32_t freq = peripherial_clock;
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uint32_t best_i = 7;
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uint32_t best_err = 0xFFFFFFFF;
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for(int i = 0; i < 8; i++){
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freq >>= 1;
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uint32_t err = (freq > speed_hz) ? (freq - speed_hz) : (speed_hz - freq);
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if(err < best_err){
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best_err = err;
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best_i = i;
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}else if(err > best_err) break;
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}
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return best_i;
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}
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// Master, 8bit, CPOL=0, CPHA=0, MSB first
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void spi_setup(uint32_t speed){ // speed in Hz
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RCC->APB2RSTR |= RCC_APB2RSTR_SPI1RST;
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RCC->APB2RSTR = 0;
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SPI1->CR1 = 0;
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uint16_t br = get_baudrate_prescaler(speed);
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SPI1->CR1 = SPI_CR1_MSTR | (br << 3) | SPI_CR1_SSM | SPI_CR1_SSI;
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SPI1->CR2 = SPI_CR2_SSOE;
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SPI1->CR1 |= SPI_CR1_SPE;
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}
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void spi_stop(){
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SPI1->CR1 &= ~SPI_CR1_SPE;
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}
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// return -1 if SPI isn't run or got error
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int spi_transfer(const uint8_t *tx, uint8_t *rx, int len){
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if(len < 1 || !(SPI1->CR1 & SPI_CR1_SPE)) return -1;
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int i;
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for(i = 0; i < len; ++i){
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uint32_t timeout = 1000000;
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while(!(SPI1->SR & SPI_SR_TXE)){
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if (--timeout == 0) return -1; // error by timeout: TX isn't ready
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}
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uint8_t out = (tx) ? tx[i] : 0;
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*(uint8_t*)&SPI1->DR = out; // ÚÁÐÉÓØ × DR
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timeout = 1000000;
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while(!(SPI1->SR & SPI_SR_RXNE)){
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if(--timeout == 0) return 0;
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}
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uint8_t in = *(uint8_t*)&SPI1->DR; // ÞÔÅÎÉÅ ÉÚ DR
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if(rx) rx[i] = in;
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}
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//while(SPI1->SR & SPI_SR_BSY){ }
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return i;
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}
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