sy7t609-uart-protocol.cpp

#include "sy7t609-uart-protocol.h"

#include <Arduino.h>

#include "sy7t609.h"

#define SSI_HEADER (0xAA)
#define SSI_DEFAULT_FRAME_SIZE (3)
#define SSI_MAX_PAYLOAD_SIZE (7)
#define SSI_READ_PAYLOAD_SIZE (4)
#define SSI_REPLY_PAYLOAD_SIZE (3)
#define SSI_WRITE_PAYLOAD_SIZE (7)

#define CMD_CLEAR_ADDRESS (0xA0)
#define CMD_SELECT_REGISTER_ADDRESS (0xA3)
#define CMD_READ_REGITSTER_3BYTES (0xE3)
#define CMD_WRITE_RETISTER_3BYTES (0xD3)

enum sy7t609_reply_code {
  REPLY_ACK_WITH_DATA = 0xAA,
  REPLY_AUTO_REPORTING_HEADER = 0xAE,
  REPLY_ACK_WITHOUT_DATA = 0xAD,
  REPLY_NEGATIVE_ACK = 0xB0,
  REPLY_COMMAND_NOT_IMPLEMENTED = 0xBC,
  REPLY_CHECKSUM_FAILED = 0xBD,
  REPLY_BUFFER_OVERFLOW = 0xBF
};

typedef struct ssi_command_packet_frame {
  uint8_t header;
  uint8_t byte_count;
  uint8_t payload[SSI_MAX_PAYLOAD_SIZE];
  uint8_t checksum;
} ssi_command_packet_frame_t;

typedef struct ssi_reply_packet_frame {
  uint8_t reply_code;
  uint8_t byte_count;
  uint8_t payload[SSI_REPLY_PAYLOAD_SIZE];
  uint8_t checksum;
} ssi_reply_packet_frame_t;

static uint8_t getChecksumForCommand(ssi_command_packet_frame_t packet);

static uint8_t getChecksumForCommand(ssi_command_packet_frame_t packet) {
  uint8_t data;
  uint8_t checksum = 0;

  data = packet.header;
  checksum += data;

  data = packet.byte_count;
  checksum += data;

  uint8_t i;
  uint8_t len = packet.byte_count - SSI_DEFAULT_FRAME_SIZE;
  for (i = 0; i < len; i++) {
    data = packet.payload[i];
    checksum += data;
  }

  checksum = ~checksum + 1;

  return checksum;
}

static uint8_t getChecksumForReply(ssi_reply_packet_frame_t packet) {
  uint8_t data;
  uint8_t checksum = 0;

  data = packet.reply_code;
  checksum += data;

  data = packet.byte_count;
  checksum += data;

  uint8_t i;
  uint8_t len = SSI_REPLY_PAYLOAD_SIZE;
  for (i = 0; i < len; i++) {
    data = packet.payload[i];
    checksum += data;
  }

  checksum = ~checksum + 1;

  return checksum;
}

bool readRegister(uint16_t addr, uint32_t* out_value) {
  ssi_command_packet_frame_t packet;

  packet.header = SSI_HEADER;

  packet.byte_count = SSI_DEFAULT_FRAME_SIZE + SSI_READ_PAYLOAD_SIZE;

  packet.payload[0] = CMD_SELECT_REGISTER_ADDRESS;
  packet.payload[1] = addr & 0xFF;
  packet.payload[2] = (addr >> 8) & 0xFF;
  packet.payload[3] = CMD_READ_REGITSTER_3BYTES;

  packet.checksum = getChecksumForCommand(packet);

  Serial.flush();

  Serial.write(packet.header);
  Serial.write(packet.byte_count);

  uint8_t i;
  for (i = 0; i < SSI_READ_PAYLOAD_SIZE; i++) {
    Serial.write(packet.payload[i]);
  }

  Serial.write(packet.checksum);

  size_t reply_len = 0;
  uint8_t reply_buffer[6];
  reply_len = Serial.readBytes(reply_buffer, 6);

  if (reply_len != 6) {
    // Serial Error
    reportErr("readRegister/Serial Error", 0);
    return false;
  }

  if (reply_buffer[0] != REPLY_ACK_WITH_DATA) {
    // SSI Error
    reportErr("readRegister/SSI Error", reply_buffer[0]);
    return false;
  }

  ssi_reply_packet_frame_t reply_packet;
  memcpy(&reply_packet, reply_buffer, sizeof(reply_packet));

  uint8_t checksum = getChecksumForReply(reply_packet);

  if (reply_packet.checksum != checksum) {
    // Checksum Error
    reportErr("readRegister/Checksum Error", 0);
    return false;
  }

  *out_value = ((uint32_t)reply_packet.payload[2] << 16) |
               ((uint32_t)reply_packet.payload[1] << 8) |
               (uint32_t)reply_packet.payload[0];

  return true;
}

bool writeRegister(uint16_t addr, uint32_t value) {
  ssi_command_packet_frame_t packet;

  packet.header = SSI_HEADER;

  packet.byte_count = SSI_DEFAULT_FRAME_SIZE + SSI_WRITE_PAYLOAD_SIZE;

  packet.payload[0] = CMD_SELECT_REGISTER_ADDRESS;
  packet.payload[1] = addr & 0xFF;
  packet.payload[2] = (addr >> 8) & 0xFF;
  packet.payload[3] = CMD_WRITE_RETISTER_3BYTES;
  packet.payload[4] = value & 0xFF;
  packet.payload[5] = (value >> 8) & 0xFF;
  packet.payload[6] = (value >> 16) & 0xFF;

  packet.checksum = getChecksumForCommand(packet);

  Serial.flush();

  Serial.write(packet.header);
  Serial.write(packet.byte_count);

  uint8_t i;
  for (i = 0; i < SSI_WRITE_PAYLOAD_SIZE; i++) {
    Serial.write(packet.payload[i]);
  }

  Serial.write(packet.checksum);

  size_t reply_len = 0;
  uint8_t reply = 0;
  reply_len = Serial.readBytes(&reply, 1);

  if (reply_len != 1) {
    // Serial Error
    reportErr("writeRegister/Serial Error", 0);
    return false;
  }

  if (reply != REPLY_ACK_WITHOUT_DATA) {
    // SSI Error
    reportErr("writeRegister/SSI Error", reply);
    return false;
  }

  return true;
}