STM32BusIORegister.cpp

/*
 * STM32BusIORegister.cpp
 *
 *  Created on: Sep 15, 2026
 *      Author: johng
 */
 
#include "STM32BusIORegister.hpp"
 
namespace {
constexpr uint8_t kAddrBit8HighToRead = 0x80;
} // namespace
 
STM32BusIORegister::STM32BusIORegister(STM32SPIDevice *spiDevice, uint32_t regAddr, size_t width, size_t addressWidth)
    : _spiDevice(spiDevice), _regAddr(regAddr), _width(width), _addressWidth(addressWidth) {
}
 
uint32_t STM32BusIORegister::read() {
    uint8_t addrBuffer[4] = {
        static_cast<uint8_t>((_regAddr & 0xFF) | kAddrBit8HighToRead),
        static_cast<uint8_t>((_regAddr >> 8) & 0xFF),
        static_cast<uint8_t>((_regAddr >> 16) & 0xFF),
        static_cast<uint8_t>((_regAddr >> 24) & 0xFF),
    };
 
    uint8_t dataBuffer[4] = {0};
    if (!_spiDevice->writeThenRead(addrBuffer, _addressWidth, dataBuffer, _width)) {
        return 0xFFFFFFFF;
    }
 
    uint32_t value = 0;
    for (size_t i = 0; i < _width; i++) {
        value <<= 8;
        value |= dataBuffer[i];
    }
    return value;
}