I2c on NRF52833 with MCP4561

RE: I2c on NRF52833 with MCP4561

sne_333 — Thu, 24 Aug 2023 05:03:55 GMT

Hi Vidar,

I am using nrf52840. I have a variable uin16_t size , and a buffer uint8_t Buf[250];. I want to write this data via I2C. How to create an I2c function for this? I tried to do the following way, but it is giving wrong results:-

bool Oled_Graphicdata(uint16_t size, uint8_t *Buff)
{

    ret_code_t err_code;

    uint8_t tx_buf[2];
	
    //Write the register address and data into transmit buffer
    tx_data[0] = ((size >> 8)& 0xFF );
    tx_data[1] = size & 0xFF;
	
    //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, 0x37, Buff, size, false);
    NRF_LOG_INFO("oled graph");
       //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)
    {
        NRF_LOG_INFO("oled graph FAILED");
        return false;
    }

    return true;	
}

I guess we need to add the Buff into tx_data. How can we do this?

Thanks & Regards,
Snehal.

RE: I2c on NRF52833 with MCP4561

Vidar Berg — Thu, 23 Jun 2022 15:24:11 GMT

Hi,

If you didn't already, please place a breakpoint inside the "NRF_DRV_TWI_EVT_DONE" event transaction and let this breakpoint get hit before you read out the twim_rx_buf buffer. This event is raised when the TX RX transfer is complete.

RE: I2c on NRF52833 with MCP4561

sne_333 — Wed, 22 Jun 2022 06:03:33 GMT

Hi Vidar,

I am reading the buffers twim_rx_buf. . Are we passing the values correctly??

I want to read register 0x00 .

RE: I2c on NRF52833 with MCP4561

Vidar Berg — Tue, 21 Jun 2022 11:33:01 GMT

Hi,

Can you please show where and how you read the RX buffer? I'm not familiar with the sensor you use, but I assume it is not supposed to echo back the command you send.

RE: I2c on NRF52833 with MCP4561

sne_333 — Tue, 21 Jun 2022 05:56:31 GMT

I guess there is something wrong going on... For reading register I did the testing with the code you provided..

#define SHT3x_ADDRESS (0x2EU)
#define SHT3x_MEAS_CMD_H {0x00, 0x0C}
static uint8_t twim_rx_buf[2];

void read_sensor_data()
{
uint32_t err_code;
static uint8_t twim_tx_buf[] = SHT3x_MEAS_CMD_H;

nrf_drv_twi_xfer_desc_t xfer_desc = NRF_DRV_TWI_XFER_DESC_TXRX(
SHT3x_ADDRESS, twim_tx_buf, sizeof(twim_tx_buf), twim_rx_buf, sizeof(twim_rx_buf));

err_code = nrf_drv_twi_xfer(&m_twi, &xfer_desc, NRF_DRV_TWI_FLAG_TX_NO_STOP);
if (err_code == NRF_ERROR_BUSY)
{
NRF_LOG_INFO("TWIM driver is busy");
}
else
{
APP_ERROR_CHECK(err_code);
}
}

Now when I read the buffer twim_rx_buf i can see values as 0x00,0x0C.

If I change the #define SHT3x_MEAS_CMD_H as {0x00, 0x0D} and again try to read then in the twim_rx_buf i can read 0x00,0x0D. why is this happening? Why is the command byte being read instead of the register value here??

RE: I2c on NRF52833 with MCP4561

sne_333 — Tue, 21 Jun 2022 05:30:00 GMT

Hi Vidar,

Yes i checked for NACK. But it was not raised. Is my code for writing correct?

Regards,

Snehal Bundele.

RE: I2c on NRF52833 with MCP4561

Vidar Berg — Mon, 20 Jun 2022 15:16:55 GMT

Hi Snehal,

You can use nrf_drv_twi_tx() to set up a write only transaction, but you should find out first if the addressed is ACKed or not. Did you check if the NRF_DRV_TWI_EVT_DATA_NACK event was raised?

Best regards,

Vidar

RE: I2c on NRF52833 with MCP4561

sne_333 — Mon, 20 Jun 2022 12:55:54 GMT

Hi Vidar,

Please reply.

Thanks & Regards,

Snehal Bundele.

RE: I2c on NRF52833 with MCP4561

sne_333 — Fri, 17 Jun 2022 12:38:51 GMT

Hi Vidar,

Thanks for sharing the code. Can you also help me with write mechanism?? How to write data along with command??

The start bit -> slave address -> command -> data -> stop bit

It will be really helpful to me.

Thanks & Regards,
Snehal.

RE: I2c on NRF52833 with MCP4561

Vidar Berg — Fri, 17 Jun 2022 12:29:49 GMT

Hi Snehal,

Please check if you are getting address "NACKs" in your TWI callback when you write to your sensor like I'm doing in the code snippet below.

/**
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 * 2. Redistributions in binary form, except as embedded into a Nordic
 *    Semiconductor ASA integrated circuit in a product or a software update for
 *    such product, must reproduce the above copyright notice, this list of
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 *    materials provided with the distribution.
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 * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * 4. This software, with or without modification, must only be used with a
 *    Nordic Semiconductor ASA integrated circuit.
 *
 * 5. Any software provided in binary form under this license must not be reverse
 *    engineered, decompiled, modified and/or disassembled.
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 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */
/** @file
 * @defgroup tw_sensor_example main.c
 * @{
 * @ingroup nrf_twi_example
 * @brief TWI Sensor Example main file.
 *
 * This file contains the source code for a sample application using TWI.
 *
 */

#include <stdio.h>
#include "boards.h"
#include "app_util_platform.h"
#include "app_error.h"
#include "nrf_drv_twi.h"
#include "nrf_delay.h"


#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"

/* TWI instance ID. */
#define TWI_INSTANCE_ID     0

/* Common addresses definition for temperature sensor. */
#define SHT3x_ADDRESS                   (0x45U)
#define SHT3x_MEAS_CMD_H                {0x2c, 0x06}                       /**<Start high repeatability measurement with clock stretching*/

/* TWI instance. */
static const nrf_drv_twi_t m_twi = NRF_DRV_TWI_INSTANCE(TWI_INSTANCE_ID);


/**
 * @brief Function for handling data from temperature sensor.
 *
 * @param[in] temp          Temperature in Celsius degrees read from sensor.
 */
__STATIC_INLINE void data_handler(nrf_drv_twi_evt_t const * p_event)
{
    uint16_t      raw_value;
    float         temperature;
    uint16_t      humidity;
    
    /* Raw data conversion. We are ignoring the checksum value here */ 
    raw_value = uint16_big_decode(&p_event->xfer_desc.p_secondary_buf[0]); /* Swap byte order to little endian */
    
    temperature = 175 * (uint16_t)raw_value / 65535.0f -45.0f;

    raw_value = uint16_big_decode(&p_event->xfer_desc.p_secondary_buf[3]);
    humidity = 100.0f * raw_value / 65535.0f;
    
    NRF_LOG_INFO("Temperature: "NRF_LOG_FLOAT_MARKER" Celsius degrees.", NRF_LOG_FLOAT(temperature));
    NRF_LOG_INFO("Humidity: %d%%", humidity);
}

/**
 * @brief TWI events handler.
 */
void twi_handler(nrf_drv_twi_evt_t const * p_event, void * p_context)
{
    switch (p_event->type)
    {
        case NRF_DRV_TWI_EVT_DONE:
            if (p_event->xfer_desc.type == NRF_DRV_TWI_XFER_TXRX)
            {
                data_handler(p_event);
            }
            break;
        case NRF_DRV_TWI_EVT_ADDRESS_NACK:
            NRF_LOG_WARNING("Received NRF_DRV_TWI_EVT_ADDRESS_NACK event");
            break;
        case NRF_DRV_TWI_EVT_DATA_NACK:
            NRF_LOG_WARNING("Received NRF_DRV_TWI_EVT_DATA_NACK event");
            break;
        default:
            break;
    }
}

/**
 * @brief UART initialization.
 */
void twi_init (void)
{
    ret_code_t err_code;

    const nrf_drv_twi_config_t twi_sht3x_config = {
       .scl                = ARDUINO_SCL_PIN,
       .sda                = ARDUINO_SDA_PIN,
       .frequency          = NRF_DRV_TWI_FREQ_100K,
       .interrupt_priority = APP_IRQ_PRIORITY_HIGH,
       .clear_bus_init     = false
    };

    err_code = nrf_drv_twi_init(&m_twi, &twi_sht3x_config, twi_handler, NULL);
    APP_ERROR_CHECK(err_code);

    nrf_drv_twi_enable(&m_twi);
}

/**
 * @brief Function for reading data from temperature sensor.
 */
static void read_sensor_data()
{  
    uint32_t err_code;
    static uint8_t twim_rx_buf[6];
    static uint8_t twim_tx_buf[] = SHT3x_MEAS_CMD_H;

    nrf_drv_twi_xfer_desc_t xfer_desc = NRF_DRV_TWI_XFER_DESC_TXRX(
        SHT3x_ADDRESS, twim_tx_buf, sizeof(twim_tx_buf), twim_rx_buf, sizeof(twim_rx_buf));

    err_code = nrf_drv_twi_xfer(&m_twi, &xfer_desc, NRF_DRV_TWI_FLAG_TX_NO_STOP);
    if (err_code == NRF_ERROR_BUSY)
    {
        NRF_LOG_INFO("TWIM driver is busy");
    }
    else
    {
        APP_ERROR_CHECK(err_code);
    }
}

/**
 * @brief Function for main application entry.
 */
int main(void)
{
    APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
    NRF_LOG_DEFAULT_BACKENDS_INIT();

    NRF_LOG_INFO("\r\nTWI SHT3x example started.");
    NRF_LOG_FLUSH();
    twi_init();

    while (true)
    {
        nrf_delay_ms(500);
        read_sensor_data();
        NRF_LOG_FLUSH();
    }
}

/** @} */

You can also use the xfer API that I used in read_sensor_data() to set up a read write transaction as shown in the datasheet figure you posted.

Driver documentation for reference: TWI master

Best regards,

Vidar

RE: I2c on NRF52833 with MCP4561

sne_333 — Fri, 17 Jun 2022 06:04:09 GMT

The reading mechanism in the datasheet is mentioned as follows:-