SpiBus.cpp

// Copyright (c) 2016-2017 Formula Slug. All Rights Reserved.

#include "SpiBus.h"

#include <cmath>
#include <cstdio>

/* Hard coded to baudrate=140.625kHz, CPHA=0, CPOL=0, MSb first
 * MCP3008's baud maxes out around 3-4MHz
 */
constexpr SPIConfig MakeConfig(SpiBusBaudRate baud, uint8_t ssPin) {
  uint16_t cr1 = 0, cr2 = 0;

  switch (baud) {
    case SpiBusBaudRate::k140k:
      cr1 = SPI_CR1_BR_2 | SPI_CR1_BR_1;
      cr2 = SPI_CR2_DS_2 | SPI_CR2_DS_1 | SPI_CR2_DS_0;
      break;
    default:
      break;
  }

  // slave selects hard-coded to port A
  return {NULL, GPIOA, ssPin, cr1, cr2};
}

SpiBus::SpiBus(SpiBusBaudRate baud, const uint8_t* slavePins,
               const uint8_t numSlaves) {
  // init private vars from params
  m_numSlaves = numSlaves;

  // init SPI pins
  // SCK
  palSetPadMode(GPIOA, 5, PAL_MODE_ALTERNATE(5) | PAL_STM32_OSPEED_HIGHEST);
  // MISO
  palSetPadMode(GPIOA, 6, PAL_MODE_ALTERNATE(5) | PAL_STM32_OSPEED_HIGHEST);
  // MOSI
  palSetPadMode(GPIOA, 7, PAL_MODE_ALTERNATE(5) | PAL_STM32_OSPEED_HIGHEST);
  // SS pins
  palSetPadMode(GPIOA, slavePins[0],
                PAL_MODE_OUTPUT_PUSHPULL | PAL_STM32_OSPEED_HIGHEST);
  palSetPadMode(GPIOA, slavePins[1],
                PAL_MODE_OUTPUT_PUSHPULL | PAL_STM32_OSPEED_HIGHEST);
  palSetPadMode(GPIOA, slavePins[2],
                PAL_MODE_OUTPUT_PUSHPULL | PAL_STM32_OSPEED_HIGHEST);
  palSetPadMode(GPIOA, slavePins[3],
                PAL_MODE_OUTPUT_PUSHPULL | PAL_STM32_OSPEED_HIGHEST);

  // create all config structs for each slave
  for (uint8_t slaveIndex = 0; slaveIndex < m_numSlaves; ++slaveIndex) {
    m_slaveConfigs[slaveIndex] = MakeConfig(baud, slavePins[slaveIndex]);
  }
}

SpiBus::~SpiBus() {
  spiUnselect(&SPID1);    // de-assert chip select
  spiReleaseBus(&SPID1);  // release ownership of bus as master
}

/*
 * @desc Reads `length` bytes from txbuf and sends over SPI bus
 */
void SpiBus::send(uint8_t length, const void* txbuf) {
  spiSend(&SPID1, length, txbuf);  // transmit
}

/*
 * @desc Writes `length` bytes into rxbuf from SPI bus
 */
void SpiBus::recv(uint8_t length, void* rxbuf) {
  spiReceive(&SPID1, length, rxbuf);  // receive
}

/*
 * @desc Acquire bus for the passed slave slave pin index
 */
void SpiBus::acquireSlave(uint8_t ssPinIndex) {
  spiAcquireBus(&SPID1);  // acquire ownership of the bus.
  spiStart(&SPID1,
           &(m_slaveConfigs[ssPinIndex]));  // setup transfer parameters.
  spiSelect(&SPID1);                        // slave Select assertion.
}

/*
 * @desc Release bus
 */
void SpiBus::releaseSlave() {
  spiUnselect(&SPID1);    // de-assert chip select
  spiReleaseBus(&SPID1);  // release ownership of bus as master
}