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]

Please check attached Logic Analyzer traces:

2 MHz, 10 M Samples [7].logicdata

RTC_Scope.csv

Please check & reply to a possible solution?

[bjorn-spockeli]

AS far as I can tell the nRF52840 is transmitting the correct data. If the address of the i2C slave is 0x6F (0b01101111), then the 7 byte address + a READ bit will be 0xDF( 0b11011111). The logic analyzer clearly states that there is a NAK after the address is transmitted. Hence, this is slave issue, not an issue with the nRF52840. I would check the connections between the nRF52840 and the MCP7940.

Best regards

Bjørn

[Vishal Aditya]

The connections are correct!
#define SCL NRF_GPIO_PIN_MAP(0,14)
#define SDA NRF_GPIO_PIN_MAP(0,13)

Connected to the same as per code via jumper wires. Please suggest any other possible way of debugging this issue. As MCP7940 works with Arduino(i2c scanner)

[Vishal Aditya]

Please check the traces of the custom board nrf52840 & MCP7940(i2c) with the same code. 

Pull-ups: 4.7kohm in custom board
but in MCP7940 break-out board, it's 10kohm

#define SCL		           				 NRF_GPIO_PIN_MAP(0,14)
#define SDA		           				 NRF_GPIO_PIN_MAP(0,13)  

//    for (address = 1; address <= TWI_ADDRESSES; address++)
//    {
				while(1)
				{
        err_code = nrf_drv_twi_rx(&m_twi, 0x6F, &sample_data, sizeof(sample_data));
        if (err_code == NRF_SUCCESS)
        {
            detected_device = true;
            NRF_LOG_INFO("TWI device detected at address 0x%x.\r\n", address);

        }
        NRF_LOG_FLUSH();
			}

[jagannathan GOPALAKRISHNAN]

Mr. bjorn, 

Kindly respond to the codes posted and suggest solutions.