ardupilot/libraries/AP_BattMonitor/AP_BattMonitor_SMBus.cpp

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#include "AP_BattMonitor_SMBus.h"
#define AP_BATTMONITOR_SMBUS_PEC_POLYNOME 0x07 // Polynome for CRC generation
AP_BattMonitor_SMBus::AP_BattMonitor_SMBus(AP_BattMonitor &mon,
AP_BattMonitor::BattMonitor_State &mon_state,
AP_BattMonitor_Params &params,
AP_HAL::OwnPtr<AP_HAL::I2CDevice> dev)
: AP_BattMonitor_Backend(mon, mon_state, params),
_dev(std::move(dev))
{
_params._serial_number = AP_BATT_SERIAL_NUMBER_DEFAULT;
_params._pack_capacity = 0;
}
void AP_BattMonitor_SMBus::init(void) {
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if (_dev) {
_dev->register_periodic_callback(100000, FUNCTOR_BIND_MEMBER(&AP_BattMonitor_SMBus::timer, void));
}
}
/// read the battery_voltage and current, should be called at 10hz
void AP_BattMonitor_SMBus::read(void)
{
// nothing to be done here for actually interacting with the battery
// however we can use this to set any parameters that need to be set
if (_serial_number != _params._serial_number) {
_params._serial_number.set_and_notify(_serial_number);
}
if (_full_charge_capacity != _params._pack_capacity) {
_params._pack_capacity.set_and_notify(_full_charge_capacity);
}
}
// reads the pack full charge capacity
// returns true if the read was successful, or if we already knew the pack capacity
bool AP_BattMonitor_SMBus::read_full_charge_capacity(void)
{
uint16_t data;
if (_full_charge_capacity != 0) {
return true;
} else if (read_word(BATTMONITOR_SMBUS_FULL_CHARGE_CAPACITY, data)) {
_full_charge_capacity = data;
return true;
}
return false;
}
// reads the remaining capacity
// returns true if the read was succesful, which is only considered to be the
// we know the full charge capacity
bool AP_BattMonitor_SMBus::read_remaining_capacity(void)
{
int32_t capacity = _params._pack_capacity;
if (capacity > 0) {
uint16_t data;
if (read_word(BATTMONITOR_SMBUS_REMAINING_CAPACITY, data)) {
_state.current_total_mah = MAX(0, capacity - data);
return true;
}
}
return false;
}
// reads the temperature word from the battery
// returns true if the read was successful
bool AP_BattMonitor_SMBus::read_temp(void)
{
uint16_t data;
if (read_word(BATTMONITOR_SMBUS_TEMP, data)) {
_state.temperature_time = AP_HAL::millis();
_state.temperature = ((float)(data - 2731)) * 0.1f;
return true;
}
return false;
}
// reads the serial number if it's not already known
// returns true if the read was successful or the number was already known
bool AP_BattMonitor_SMBus::read_serial_number(void) {
uint16_t data;
// don't recheck the serial number if we already have it
if (_serial_number != -1) {
return true;
} else if (read_word(BATTMONITOR_SMBUS_SERIAL, data)) {
_serial_number = data;
return true;
}
return false;
}
// read word from register
// returns true if read was successful, false if failed
bool AP_BattMonitor_SMBus::read_word(uint8_t reg, uint16_t& data) const
{
// buffer to hold results (1 extra byte returned holding PEC)
const uint8_t read_size = 2 + (_pec_supported ? 1 : 0);
uint8_t buff[read_size]; // buffer to hold results
// read the appropriate register from the device
if (!_dev->read_registers(reg, buff, sizeof(buff))) {
return false;
}
// check PEC
if (_pec_supported) {
const uint8_t pec = get_PEC(AP_BATTMONITOR_SMBUS_I2C_ADDR, reg, true, buff, 2);
if (pec != buff[2]) {
return false;
}
}
// convert buffer to word
data = (uint16_t)buff[1]<<8 | (uint16_t)buff[0];
// return success
return true;
}
/// get_PEC - calculate packet error correction code of buffer
uint8_t AP_BattMonitor_SMBus::get_PEC(const uint8_t i2c_addr, uint8_t cmd, bool reading, const uint8_t buff[], uint8_t len) const
{
// exit immediately if no data
if (len == 0) {
return 0;
}
// prepare temp buffer for calcing crc
uint8_t tmp_buff[len+3];
tmp_buff[0] = i2c_addr << 1;
tmp_buff[1] = cmd;
tmp_buff[2] = tmp_buff[0] | (uint8_t)reading;
memcpy(&tmp_buff[3],buff,len);
// initialise crc to zero
uint8_t crc = 0;
uint8_t shift_reg = 0;
bool do_invert;
// for each byte in the stream
for (uint8_t i=0; i<sizeof(tmp_buff); i++) {
// load next data byte into the shift register
shift_reg = tmp_buff[i];
// for each bit in the current byte
for (uint8_t j=0; j<8; j++) {
do_invert = (crc ^ shift_reg) & 0x80;
crc <<= 1;
shift_reg <<= 1;
if(do_invert) {
crc ^= AP_BATTMONITOR_SMBUS_PEC_POLYNOME;
}
}
}
// return result
return crc;
}