/*
 * This file is part of the as3935 project.
 * Copyright 2026 Edward V. Emelianov <edward.emelianoff@gmail.com>.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */


#include "spi.h"
#include "hardware.h"
#include "commproto.h"

// CR1 register default values
// Fpclk/64
static const uint32_t SPI_CR1 = SPI_CR1_MSTR | SPI_CR1_BR_2 | SPI_CR1_BR_0 | SPI_CR1_SSM | SPI_CR1_SSI | SPI_CR1_CPHA /* | SPI_CR1_CPOL*/;

spiStatus SPI_status = SPI_NOTREADY;
uint8_t as3935_channel = 0;

void spi_setup(){
    // master, no slave select, BR=F/16, CPOL/CPHA - polarity.
    SPI1->CR1 = SPI_CR1;
    SPI_status = SPI_READY;
    SPI1->CR1 |= SPI_CR1_SPE; // enable SPI
}

volatile uint32_t wctr;
#define WAITX(x)  do{wctr = 0; while((x) && (++wctr < 360000)) IWDG->KR = IWDG_REFRESH; if(wctr==360000) return -1;}while(0)

/**
 * @brief SPI_transmit - transmit data and receive new one
 * @param buf - data to transmit/receive
 * @param len - its length
 * @return amount of transmitted data or -1 if error
 */
uint8_t SPI_transmit(uint8_t *buf, uint8_t len){
    if(!buf || !len) return 0; // bad data format
    if(SPI_status != SPI_READY) return 0; // spi not ready to transmit data
    CS(as3935_channel);
    for(uint8_t x = 0; x < len; ++x){
        WAITX(!(SPI1->SR & SPI_SR_TXE));
        SPI1->DR = buf[x];
        WAITX(!(SPI1->SR & SPI_SR_BSY));
        WAITX(!(SPI1->SR & SPI_SR_RXNE));
        buf[x] = SPI1->DR;
    }
    CS_OFF();
    return len;
}