MCP7940 drivers for nrf52840

[Vishal Aditya]

We are working on external RTC MCP7940(i2c) interfaced with nrf52840. Please check if drivers of the same for nrf52/51 are available or any implementation of CLOCK using MCP7940 with NRF?

Regards

Vishal Aditya

Embedded Software Engineer

[Vishal Aditya]

Yes getting 0x80

Below is the attached Arduino init sequence:

  Wire.begin();                               // Start I2C as master device
  Wire.setClock(i2cSpeed);                    // Set the I2C bus speed
  Wire.beginTransmission(MCP7940_ADDRESS);    // Address the MCP7940M
  uint8_t errorCode = Wire.endTransmission(); // See if there's a device present
  if (errorCode == 0)                         // If we have a MCP7940M
  {
    clearRegisterBit(MCP7940_RTCHOUR, MCP7940_12_24);                      // Use 24 hour clock
    setRegisterBit(MCP7940_CONTROL, MCP7940_ALMPOL);                       // assert alarm low, default high
    _CrystalStatus = readRegisterBit(MCP7940_RTCSEC, MCP7940_ST);          // Status bit from register
    _OscillatorStatus = readRegisterBit(MCP7940_RTCWKDAY, MCP7940_OSCRUN); // Oscillator state from register
  }

MCP7940.h

MCP7940.cpp

[bjorn-spockeli]

Great, then you are good to go. You should be able to reuse the snippet I provided to configure the MCP7940.  My suggestion would be to capture a trace of the Arduino Init sequence to see which values that are written to which register and then just copy paste the code snippet I provided and change the REG_RTCSEC register value and the 0x80 to match what you're seeing in the trace.