MCP7940 drivers for nrf52840

RE: MCP7940 drivers for nrf52840

bjorn-spockeli — Thu, 05 Mar 2020 10:20:45 GMT

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.

RE: MCP7940 drivers for nrf52840

Vishal Aditya — Thu, 05 Mar 2020 09:00:31 GMT

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
  }

devzone.nordicsemi.com/.../MCP7940.h

devzone.nordicsemi.com/.../MCP7940.cpp

RE: MCP7940 drivers for nrf52840

bjorn-spockeli — Thu, 05 Mar 2020 07:44:18 GMT

Ok, if the nrf_drv_twi_rx call does not return a non-zero error code, then things are working as they should. Could you try to run the following code and see if the rx_data[0] is 0x80. If it is then the code is working as intended.

// Initizalize buffers 	
uint8_t tx_data[] = {REG_RTCSEC, 0x80 }; // Set TX buffer - Write 0x80 ( Enable Osc) to REG_RTCSEC register
uint8_t rx_data[] = {}; // Empty RX buffer

// Write Tx data to MCP7940
err_code = nrf_drv_twi_tx(&m_twi,MCP7940_I2C,tx_data , sizeof(tx_data),false);
APP_ERROR_CHECK(err_code);

// Select REG_RTCSEC register and use repeated start (only send 1 byte of tx buffer)
err_code = nrf_drv_twi_tx(&m_twi,MCP7940_I2C,tx_data , 1 ,true);
APP_ERROR_CHECK(err_code);

// Read REG_RTCSEC register 
err_code = nrf_drv_twi_rx(&m_twi,MCP7940_I2C,rx_data,1);
APP_ERROR_CHECK(err_code);

Best regards

Bjørn

RE: MCP7940 drivers for nrf52840

Vishal Aditya — Thu, 05 Mar 2020 06:06:59 GMT

err_code = 0

RE: MCP7940 drivers for nrf52840

bjorn-spockeli — Wed, 04 Mar 2020 12:21:47 GMT

Yes, but you are reading back the value of the register, i.e. 0x07. Wasnt that what you wrote to the register previously? What is the return code of nrf_drv_twi_rx()? Is it NRF_ERROR_DRV_TWI_ERR_DNACK or NRF_ERROR_DRV_TWI_ERR_ANACK?

RE: MCP7940 drivers for nrf52840

Vishal Aditya — Wed, 04 Mar 2020 10:50:51 GMT

Please check still NAK

RE: MCP7940 drivers for nrf52840

bjorn-spockeli — Wed, 04 Mar 2020 08:56:47 GMT

If you want to start the oscillator, then you need to set bit 7 in REG_RTCSEC to 1, i.e. you need to write 0x80 not 0x07.

The read operation is Not Acknowledged so it could be that you have to select the register you want to read from before

// Read REG_RTCSEC register

uint8_t tx_data[] = {REG_RTCSEC };
uint8_t rx_data[] = {0};

// Select REG_RTCSEC register and use repeated start
err_code = nrf_drv_twi_tx(&m_twi,MCP7940_I2C,tx_data , sizeof(tx_data),true);
APP_ERROR_CHECK(err_code);

// Read REG_RTCSEC register
err_code = nrf_drv_twi_rx(&m_twi,MCP7940_I2C,rx_data,1);
APP_ERROR_CHECK(err_code);

RE: MCP7940 drivers for nrf52840

Vishal Aditya — Wed, 04 Mar 2020 07:44:57 GMT

Pls check

const uint8_t  MCP7940_ST                =         7; ///< MCP7940 register bits. RTCSEC reg
//REST variables remains same as above
	while(1)
	{
	uint8_t tx_data[] = {REG_RTCSEC, MCP7940_ST };
	uint8_t rx_data[] = REG_RTCSEC;

	//trying to start oscillator
		err_code = nrf_drv_twi_tx(&m_twi,MCP7940_I2C,tx_data , sizeof(tx_data),false);
		APP_ERROR_CHECK(err_code);
	  err_code = nrf_drv_twi_rx(&m_twi,MCP7940_I2C,rx_data,1);
		nrf_delay_ms(1);
    }

RE: MCP7940 drivers for nrf52840

bjorn-spockeli — Mon, 02 Mar 2020 14:47:48 GMT

Yes, now you are writing to register with address 0x02 of the device with address 0xDE, but you are not providing the value you want to write to register 0x02.

uint8_t tx_data[] = {REG_RTCHOUR, <value to write to REG_RTCHOUR register> };

err_code = nrf_drv_twi_tx(&m_twi,MCP7940_I2C,tx_data , sizeof(tx_data));

APP_ERROR_CHECK(err_code)

RE: MCP7940 drivers for nrf52840

Vishal Aditya — Mon, 02 Mar 2020 09:58:12 GMT

Pls check the trace of REG_RTCHOUR,

const uint8_t MCP7940_RTCHOUR = 0x02; ///< Timekeeping, RTCHOUR Register address

RE: MCP7940 drivers for nrf52840

Vishal Aditya — Sat, 29 Feb 2020 07:02:23 GMT

Custom defined which works as below:

https://www.arduino.cc/reference/en/language/functions/bits-and-bytes/bitclear/

https://www.arduino.cc/reference/en/language/functions/bits-and-bytes/bitset/

Will update the traces & API call as per this soon!

[quote userid="7571" url="~/f/nordic-q-a/54222/mcp7940-drivers-for-nrf52840/237133"][/quote]

uint8_t tx_data = REG_RTCHOUR;

err_code = nrf_drv_twi_tx(&m_twi,MCP7940_I2C,&tx_data , sizeof(tx_data));

APP_ERROR_CHECK(err_code)

RE: MCP7940 drivers for nrf52840

bjorn-spockeli — Fri, 28 Feb 2020 13:02:20 GMT

The trace clearly show that its only the MCP7940_I2C address that is transmitted. The nrf_drv_twi_tx documentation states that the data passed to it should be a uint8_t pointer, so try passing it like this

uint8_t tx_data = REG_RTCHOUR;

err_code = nrf_drv_twi_tx(&m_twi,MCP7940_I2C,&tx_data , sizeof(tx_data));

APP_ERROR_CHECK(err_code)

Furthermore what does the bitClear (registerValue, 6) and bitSet (registerValue, 6) functions do? You are passing they're return value as the length parameter to nrf_drv_twi_tx and nrf_drv_twi_rx.

void init_MCP7940() {

    char registerValue = 0x00; // Holds the received register value
    char twelveHour = 0x00; // 0 = 24 Hour Clock Mode / 1 = 12 Hour Clock Mode
    char startClock = 0x01; // 0 = Start Oscillator / 1 = Stop Oscillator
    
    // Turn on/off: 12 hour vs. 24 hour clock
    err_code = nrf_drv_twi_tx(&m_twi,MCP7940_I2C, REG_RTCHOUR, 1);
    err_code = nrf_drv_twi_rx(&m_twi, MCP7940_I2C, registerValue, sizeof(MCP7940_I2C));
    
    if (twelveHour == 0x00) err_code = nrf_drv_twi_tx(&m_twi,MCP7940_I2C, REG_RTCHOUR, bitClear (registerValue, 6));
    if (twelveHour == 0x01) err_code = nrf_drv_twi_tx(&m_twi,MCP7940_I2C, REG_RTCHOUR, bitSet (registerValue, 6));
    
    // Turn on/off: Oscillator (starts the clock)
    err_code = nrf_drv_twi_rx(&m_twi, MCP7940_I2C, registerValue, 1);
    
    if (startClock == 0x00) err_code = nrf_drv_twi_tx(&m_twi,MCP7940_I2C, REG_RTCSEC, bitClear (registerValue, 7));
    if (startClock == 0x01) err_code = nrf_drv_twi_tx(&m_twi,MCP7940_I2C, REG_RTCSEC, bitSet (registerValue, 7));

}

RE: MCP7940 drivers for nrf52840

Vishal Aditya — Fri, 28 Feb 2020 11:49:18 GMT

Yes calling init_MCP7940()

Below register maps:

const uint8_t MCP7940_I2C = 0xDE;
const uint8_t MCP7940_RTCSEC = 0x00; ///< Timekeeping, RTCSEC Register address
const uint8_t MCP7940_RTCMIN = 0x01; ///< Timekeeping, RTCMIN Register address
const uint8_t MCP7940_RTCHOUR = 0x02; ///< Timekeeping, RTCHOUR Register address
const uint8_t MCP7940_RTCWKDAY = 0x03; ///< Timekeeping, RTCWKDAY Register address
const uint8_t MCP7940_RTCDATE = 0x04; ///< Timekeeping, RTCDATE Register address
const uint8_t MCP7940_RTCMTH = 0x05; ///< Timekeeping, RTCMTH Register address
const uint8_t MCP7940_RTCYEAR = 0x06; ///< Timekeeping, RTCYEAR Register address
const uint8_t MCP7940_CONTROL = 0x07; ///< Timekeeping, RTCCONTROL Register address
const uint8_t MCP7940_OSCTRIM = 0x08; ///< Timekeeping, RTCOSCTRIM Register address
const uint8_t MCP7940_ALM0SEC = 0x0A; ///< Alarm 0, ALM0SEC Register address
const uint8_t MCP7940_ALM0MIN = 0x0B; ///< Alarm 0, ALM0MIN Register address
const uint8_t MCP7940_ALM0HOUR = 0x0C; ///< Alarm 0, ALM0HOUR Register address
const uint8_t MCP7940_ALM0WKDAY = 0x0D; ///< Alarm 0, ALM0WKDAY Register address
const uint8_t MCP7940_ALM0DATE = 0x0E; ///< Alarm 0, ALM0DATE Register address
const uint8_t MCP7940_ALM0MTH = 0x0F; ///< Alarm 0, ALM0MTH Register address
const uint8_t MCP7940_ALM1SEC = 0x11; ///< Alarm 1, ALM1SEC Register address
const uint8_t MCP7940_ALM1MIN = 0x12; ///< Alarm 1, ALM1MIN Register address
const uint8_t MCP7940_ALM1HOUR = 0x13; ///< Alarm 1, ALM1HOUR Register address
const uint8_t MCP7940_ALM1WKDAY = 0x14; ///< Alarm 1, ALM1WKDAY Register address
const uint8_t MCP7940_ALM1DATE = 0x15; ///< Alarm 1, ALM1DATE Register address
const uint8_t MCP7940_ALM1MTH = 0x16; ///< Alarm 1, ALM1MONTH Register address
const uint8_t MCP7940_PWRDNMIN = 0x18; ///< Power-Fail, PWRDNMIN Register address
const uint8_t MCP7940_PWRDNHOUR = 0x19; ///< Power-Fail, PWRDNHOUR Register address
const uint8_t MCP7940_PWRDNDATE = 0x1A; ///< Power-Fail, PWDNDATE Register address
const uint8_t MCP7940_PWRDNMTH = 0x1B; ///< Power-Fail, PWRDNMTH Register address
const uint8_t MCP7940_PWRUPMIN = 0x1C; ///< Power-Fail, PWRUPMIN Register address
const uint8_t MCP7940_PWRUPHOUR = 0x1D; ///< Power-Fail, PWRUPHOUR Register address
const uint8_t MCP7940_PWRUPDATE = 0x1E; ///< Power-Fail, PWRUPDATE Register address
const uint8_t MCP7940_PWRUPMTH = 0x1F; ///< Power-Fail, PWRUPMTH Register address
const uint8_t MCP7940_RAM_ADDRESS = 0x20; ///< NVRAM - Start address for SRAM
const uint8_t MCP7940_ST = 7; ///< MCP7940 register bits. RTCSEC reg
const uint8_t MCP7940_12_24 = 6; ///< RTCHOUR, PWRDNHOUR & PWRUPHOUR
const uint8_t MCP7940_AM_PM = 5; ///< RTCHOUR, PWRDNHOUR & PWRUPHOUR
const uint8_t MCP7940_OSCRUN = 5; ///< RTCWKDAY register
const uint8_t MCP7940_PWRFAIL = 4; ///< RTCWKDAY register
const uint8_t MCP7940_VBATEN = 3; ///< RTCWKDAY register
const uint8_t MCP7940_LPYR = 5; ///< RTCMTH register
const uint8_t MCP7940_OUT = 7; ///< CONTROL register
const uint8_t MCP7940_SQWEN = 6; ///< CONTROL register
const uint8_t MCP7940_ALM1EN = 5; ///< CONTROL register
const uint8_t MCP7940_ALM0EN = 4; ///< CONTROL register
const uint8_t MCP7940_EXTOSC = 3; ///< CONTROL register
const uint8_t MCP7940_CRSTRIM = 2; ///< CONTROL register
const uint8_t MCP7940_SQWFS1 = 1; ///< CONTROL register
const uint8_t MCP7940_SQWFS0 = 0; ///< CONTROL register
const uint8_t MCP7940_SIGN = 7; ///< OSCTRIM register
const uint8_t MCP7940_ALMPOL = 7; ///< ALM0WKDAY register
const uint8_t MCP7940_ALM0IF = 3; ///< ALM0WKDAY register
const uint8_t MCP7940_ALM1IF = 3; ///< ALM1WKDAY register
const uint32_t SECONDS_PER_DAY = 86400; ///< 60 secs * 60 mins * 24 hours
const uint32_t SECONDS_FROM_1970_TO_2000 = 946684800; ///< Seconds between year 1970 and 2000

Please let me know if any traces required at any line with break-point? Also, I can send the drivers again with a private link to your INBOX it is required?

RE: MCP7940 drivers for nrf52840

bjorn-spockeli — Wed, 26 Feb 2020 12:56:30 GMT

Are you calling the init_MCP7940() function at all? You seem to be writting to the same register (0xDE) over and over again. Does 0xDE correspond with REG_RTCHOUR or REG_RTCSEC?

RE: MCP7940 drivers for nrf52840

Vishal Aditya — Wed, 26 Feb 2020 11:59:39 GMT

pls guide or let me know further which transactions traces required will update it

RE: MCP7940 drivers for nrf52840

bjorn-spockeli — Wed, 26 Feb 2020 10:53:33 GMT

Please attach a logic trace of the I2C lines when you run the init_MCP7940() function.

RE: MCP7940 drivers for nrf52840

Vishal Aditya — Wed, 26 Feb 2020 10:47:53 GMT

Hi,
I am trying to do init sequence but not able to START Clock Oscillator of MCP7940

void init_MCP7940() {

char registerValue = 0x00; // Holds the received register value
char twelveHour = 0x00; // 0 = 24 Hour Clock Mode / 1 = 12 Hour Clock Mode
char startClock = 0x01; // 0 = Start Oscillator / 1 = Stop Oscillator

// Turn on/off: 12 hour vs. 24 hour clock
err_code = nrf_drv_twi_tx(&m_twi,MCP7940_I2C, REG_RTCHOUR, 1);
err_code = nrf_drv_twi_rx(&m_twi, MCP7940_I2C, registerValue, sizeof(MCP7940_I2C));

if (twelveHour == 0x00) err_code = nrf_drv_twi_tx(&m_twi,MCP7940_I2C, REG_RTCHOUR, bitClear (registerValue, 6));
if (twelveHour == 0x01) err_code = nrf_drv_twi_tx(&m_twi,MCP7940_I2C, REG_RTCHOUR, bitSet (registerValue, 6));

// Turn on/off: Oscillator (starts the clock)
err_code = nrf_drv_twi_rx(&m_twi, MCP7940_I2C, registerValue, 1);

if (startClock == 0x00) err_code = nrf_drv_twi_tx(&m_twi,MCP7940_I2C, REG_RTCSEC, bitClear (registerValue, 7));
if (startClock == 0x01) err_code = nrf_drv_twi_tx(&m_twi,MCP7940_I2C, REG_RTCSEC, bitSet (registerValue, 7));

}

RE: MCP7940 drivers for nrf52840

bjorn-spockeli — Mon, 06 Jan 2020 15:01:54 GMT

All write transactions are now followed by an ACK, which means that the MCP7940 is responding correctly. You could now try to send the I2C transaction that returns the time from the MCP7940.

RE: MCP7940 drivers for nrf52840

Vishal Aditya — Mon, 06 Jan 2020 10:32:49 GMT

Please check the traces after code updates:

    twi_init();

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

        }
        NRF_LOG_FLUSH();
			}
    

    if (!detected_device)
    {
        NRF_LOG_INFO("No device was found.\r\n");
        NRF_LOG_FLUSH();
    }

RE: MCP7940 drivers for nrf52840

bjorn-spockeli — Fri, 03 Jan 2020 14:07:56 GMT

With the Arduino you are writting to a device with address 0x6F, not reading from it. So if you want to do exactly the same with the nRF52840, then you need to replace nrf_drv_twi_rx with nrf_drv_twi_tx.

RE: MCP7940 drivers for nrf52840

Vishal Aditya — Fri, 03 Jan 2020 09:56:30 GMT

Sampling for 5secs:

Please check the traces of MCP_Breakout with Arduino:

With Arduino, MCP Works properly able to do i2c, SET & GET DATETIME

Arduino Code:

#include <Wire.h>
 
 
void setup()
{
  Wire.begin();
 
  Serial.begin(115200);
  while (!Serial);             // Leonardo: wait for serial monitor
  Serial.println("\nI2C Scanner");
}
 
 
void loop()
{
  byte error, address;
  int nDevices;
 
  Serial.println("Scanning...");
 
  nDevices = 0;
  //for(address = 1; address < 127; address++ )
  while(1)
  {
//SENDING 0x6F in decimal as per arduino Wire library
    Wire.beginTransmission(111);
    error = Wire.endTransmission();
 
    if (error == 0)
    {
      Serial.print("I2C device found at address 0x");
      if (address<16)
        Serial.print("0");
      Serial.print(address,HEX);
      Serial.println("  !");
 
      nDevices++;
    }
    else if (error==4)
    {
      Serial.print("Unknown error at address 0x");
      if (address<16)
        Serial.print("0");
      Serial.println(address,HEX);
    }    
  }
  if (nDevices == 0)
    Serial.println("No I2C devices found\n");
  else
    Serial.println("done\n");
 
  //delay(5000);           // wait 5 seconds for next scan
}

Please reply for a possible way of the solution!

RE: MCP7940 drivers for nrf52840

bjorn-spockeli — Thu, 02 Jan 2020 15:09:02 GMT

The traces still show that the slave, i.e. MCP7940 is not ACKing the read. Can you enable the analog sampling in addition to the digital sampling of the salea? That way we can see if the MCP7940 is attempting to pull eh the SDA line high or not. Also how large is sample_data?

What does the trace from the Arduino look like? Does it try to read the same address as the one in the trace below? Have you compared the traces?

RE: MCP7940 drivers for nrf52840

jagannathan GOPALAKRISHNAN — Tue, 24 Dec 2019 08:19:00 GMT

Mr. bjorn,

Kindly respond to the codes posted and suggest solutions.

RE: MCP7940 drivers for nrf52840

Vishal Aditya — Fri, 20 Dec 2019 10:11:19 GMT

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();
			}

RE: MCP7940 drivers for nrf52840

Vishal Aditya — Fri, 20 Dec 2019 06:46:11 GMT

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)