NRF52840 I2C ADDRESS.

RE: NRF52840 I2C ADDRESS.

Kenneth — Mon, 14 Feb 2022 16:47:16 GMT

Please get a logic analyzer so you can observe the data.

Kenneth

RE: NRF52840 I2C ADDRESS.

sne_333 — Mon, 14 Feb 2022 13:03:16 GMT

Hi Kenneth,

I tried doing that also but no luck. The strange part is when I try to initialize it using the function below, I get a SUCCESS message, but when I try to send data to samd20 nothing is being received on samd20.

SAMD20_ADDR = 0X54;

bool samd20_i2c_init(void)
{
ret_code_t err_code;
// uint8_t address = 0x54;
uint8_t sample_data = 0x00;

err_code = nrf_drv_twi_rx(&m_twi,SAMD20_ADDR,&sample_data,sizeof(sample_data));
if(err_code == NRF_SUCCESS)
{
NRF_LOG_INFO("SUCCESS 999");
//flag_led = 1;
return true;
}
else
{
NRF_LOG_INFO("FAILED");
return false;
}

}

I don't understand why I am not receiving anything on SAMD20.I am really stuck here badly and not understanding how to proceed.

Thanks & Regards,

Snehal.

RE: NRF52840 I2C ADDRESS.

Kenneth — Mon, 14 Feb 2022 12:52:34 GMT

Looking at the api for nrf_drv_twi_tx() there is nothing preventing you from just set the first byte of p_data to your value instead of register_adress.

/**
 * @brief Function for sending data to a TWI slave.
 *
 * The transmission will be stopped when an error occurs. If a transfer is ongoing,
 * the function returns the error code @ref NRF_ERROR_BUSY.
 *
 * @param[in] p_instance Pointer to the driver instance structure.
 * @param[in] address    Address of a specific slave device (only 7 LSB).
 * @param[in] p_data     Pointer to a transmit buffer.
 * @param[in] length     Number of bytes to send.
 * @param[in] no_stop    If set, the stop condition is not generated on the bus
 *                       after the transfer has completed successfully (allowing
 *                       for a repeated start in the next transfer).
 *
 * @retval NRF_SUCCESS                  If the procedure was successful.
 * @retval NRF_ERROR_BUSY               If the driver is not ready for a new transfer.
 * @retval NRF_ERROR_INTERNAL           If an error was detected by hardware.
 * @retval NRF_ERROR_INVALID_ADDR       If the EasyDMA is used and memory adress in not in RAM.
 * @retval NRF_ERROR_DRV_TWI_ERR_ANACK  If NACK received after sending the address in polling mode.
 * @retval NRF_ERROR_DRV_TWI_ERR_DNACK  If NACK received after sending a data byte in polling mode.
 */
__STATIC_INLINE
ret_code_t nrf_drv_twi_tx(nrf_drv_twi_t const * p_instance,
                          uint8_t               address,
                          uint8_t const *       p_data,
                          uint8_t               length,
                          bool                  no_stop);

Best regards,
Kenneth

RE: NRF52840 I2C ADDRESS.

sne_333 — Mon, 14 Feb 2022 10:33:06 GMT

Hi Kenneth,

I am not having logic analyzer. I am not confusing between 2 addresses. I understand that slave address is used as an identifier by the master and register address is internal addresses of the slave device. But in my case, I dont have any registers in my slave device. So how to send data?? What to put in place of register address?

Thanks & Regards,

Snehal.

RE: NRF52840 I2C ADDRESS.

Kenneth — Mon, 14 Feb 2022 10:30:26 GMT

I believe you are mixing a bit the Device (slave) address with the Register address(es). There are two typical sequences in 2-wire (I2C) transactions, to illustrate the write and read operations you can look at the below Figures:

I suggest that you add a logic analyzer to the 2-wire (I2C) pins to see the actual data.

Kenneth

RE: NRF52840 I2C ADDRESS.

sne_333 — Mon, 14 Feb 2022 09:22:00 GMT

Hi Kenneth,

I had one question. I have a I2c slave device SAMD20, I am able to initiate a connection with samd20. Now I want to send sample data "0xaa" through I2c. SAMD20 has no registers. It is directly configured as a slave device with slave id 0x54. How can i send data through i2c??

I am trying to use this code:-

bool samd20_register_write(uint8_t register_address, uint8_t value)
{
ret_code_t err_code;
uint8_t tx_buf[SAMD20_ADDRESS_LEN+1];

//Write the register address and data into transmit buffer
tx_buf[0] = register_address;
tx_buf[1] = value;

//Set the flag to false to show the transmission is not yet completed
m_xfer_done = false;

//Transmit the data over TWI Bus
err_code = nrf_drv_twi_tx(&m_twi, SAMD20_ADDRESS, tx_buf, SAMD20_ADDRESS_LEN+1, false);

//Wait until the transmission of the data is finished
while (m_xfer_done == false)
{
}

// if there is no error then return true else return false
if (NRF_SUCCESS != err_code)
{
return false;
}

return true;
}

But I am confused what should I pass as register address?? I have only slave address configured in the slave which is 0x54. SAMD20_ADDRESS =0x54. How do I send data ??

samd20_register_write(register_address, 0xaa);

Please help me on this.

RE: NRF52840 I2C ADDRESS.

Kenneth — Mon, 24 Jan 2022 08:28:41 GMT

Hi,

Good to hear you have solved it. There should be nothing in specific needed to handle 3 slaves, you only need to update the address for each slave, and also I suggest wait for the previous transaction to complete before starting the next.

Kenneth

RE: NRF52840 I2C ADDRESS.

sne_333 — Mon, 24 Jan 2022 07:21:50 GMT

Hi Kenneth,

Thanks for your reply. I solved that issue. Now my question is I have 3 slaves connected to NRF52840 on the same I2C lines SCL pin as P1.09 and SDA pin as P0.11. I am able to connect to slave 1. Now for adding slave 2 and slave 3 do I need to add something extra or I can read all 3 slaves from the same instance??

Warm Regards,

Snehal.

RE: NRF52840 I2C ADDRESS.

Kenneth — Tue, 18 Jan 2022 12:26:12 GMT

You can use the following macro from nrf_gpio.h:

/** @brief Macro for mapping port and pin numbers to values understandable for nrf_gpio functions. */
#define NRF_GPIO_PIN_MAP(port, pin) (((port) << 5) | ((pin) & 0x1F))

e.g. scl = NRF_GPIO_PIN_MAP(1,9);

RE: NRF52840 I2C ADDRESS.

sne_333 — Tue, 18 Jan 2022 11:25:00 GMT

Thanks, I got it. I had one question. I tested my code with SDA and SCL lines as p026 and p027. Now if I want to use SCL pin as P1.09 and SDA pin as P0.11 how do I configure port 1 and port 0 seperately?

RE: NRF52840 I2C ADDRESS.

Kenneth — Mon, 17 Jan 2022 21:08:12 GMT

I think I read somewhere that the ATSAMD20 can support multiple (e.g. 2) i2c slave addresses?

Kenneth

RE: NRF52840 I2C ADDRESS.

sne_333 — Mon, 17 Jan 2022 12:24:07 GMT

Thanks for your reply Kenneth. Something weird is happening at my side. I agree with your left bit shifting. I tried to test the code again. Now NRF52840 is scanning 2 addresses.

my code is as follows:-

int main(void){

ret_code_t err_code;
uint8_t address = (0x54U);
uint8_t data;
bool detected_device = false;
bool result = false;

APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
NRF_LOG_DEFAULT_BACKENDS_INIT();

NRF_LOG_INFO("TWI scanner started.");
NRF_LOG_FLUSH();
twi_init();
nrf_delay_ms(1000); // give some delay

for (address = 1; address <= TWI_ADDRESSES; address++)
{
err_code = nrf_drv_twi_rx(&m_twi, address, &data, sizeof(data));
if (err_code == NRF_SUCCESS)
{
detected_device = true;
NRF_LOG_INFO("TWI device detected at address 0x%x...0x%x", address,data);
NRF_LOG_FLUSH();
send_data();
}
NRF_LOG_FLUSH();
}

void send_data(void)
{
ret_code_t err_code;
uint8_t address = (0x54U);
uint8_t sample_data=0xaa;
uint8_t sample_data1;

err_code = nrf_drv_twi_tx(&m_twi, address, &sample_data, sizeof(sample_data), true);
//Wait for the transmission to get completed
//while (m_xfer_done == false){}
nrf_delay_ms(1000); // give some delay

// If transmission was not successful, exit the function with false as return value
if (NRF_SUCCESS != err_code)
{
NRF_LOG_INFO("FAILED 1.");
NRF_LOG_FLUSH();
}
else
{
NRF_LOG_INFO("SUCCESS 1.");
NRF_LOG_FLUSH();
}

}

This is my log on nrf module :-

<info> app: TWI scanner started.
<info> app: TWI device detected at address 0x28...0x0
<info> app: SUCCESS 1.
<info> app: TWI device detected at address 0x54...0xAA
<info> app: SUCCESS 1.

0XAA is the data which I had sent to the slave. Now why is it scanning 2 addresses when I have attached only one slave with address 0x54??

RE: NRF52840 I2C ADDRESS.

Kenneth — Mon, 17 Jan 2022 11:41:00 GMT

Typically i2c is 7-bit address followed by an 8th-bit that indicate read or write. Making up a total of 8-bit i2c transaction. When there is mismatch between i2c address set and the actual i2c address that the scanner finds, then it typically due to a bit shifting that occured when creating the 7-bit address on the slave (typically done by shifting the address one bit to the left, there one bit can be masked out). It is likely this is the case here, but you may need to try several adresses or use a logic analyzer to more easily understand this.

0x54: 01010100 (shifting 1bit to the left and masking out the MSB: 0101000).
0x28: 00101000

At least that is what I expect.

Best regards,
Kenneth