RE: twi can't read data from sensor

haakonsh — Mon, 23 Mar 2020 13:21:15 GMT

Can you share a scope of the SDA and SCL lines?

[quote user="lisi"]that you need to retry at a later point. [/quote]

It means that the driver is busy with the last transaction and that you need to wait until the last transaction has completed until you can issue another one.

RE: twi can't read data from sensor

lisi — Fri, 20 Mar 2020 13:31:36 GMT

I used an oscilloscope to grab the waveform of the SCL line, and there was no waveform change after the application reported an NRF_ERROR_BUSY error. I debug found that the applocation is stop at while (m_xfer_done == false);

[quote userid="13562" url="~/f/nordic-q-a/59271/twi-can-t-read-data-from-sensor/240850"] that you need to retry at a later point. [/quote]

Sorry, I didn't understand what that meant

RE: twi can't read data from sensor

haakonsh — Fri, 20 Mar 2020 12:05:31 GMT

NRF_ERROR_BUSY means that the TWI peripheral is still in a transaction and that you need to retry at a later point.

[quote user="lisi"]I use oscilloscope, at first there is level conversion, then there is no.[/quote]

I do not know what that means, can you share a scope of the TWI lines?

RE: twi can't read data from sensor

lisi — Fri, 20 Mar 2020 10:27:41 GMT

Hi,

I use oscilloscope, at first there is level conversion, then there is no.

I used analog I2c could add the delay function after sent/written the read address by the master.

Below is the main.c file

/** @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        HTU21D_SlaveAddress   (0x80U>>1)          //¶¨ÒåHTU21DÔÚI2C×ÜÏßÉÏµÄ´ÓµØÖ·

/* Mode for LM75B. */
#define NORMAL_MODE 0U

/* Indicates if operation on TWI has ended. */
static volatile bool m_xfer_done = false;

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

/* Buffer for samples read from temperature sensor. */
static uint8_t m_sample;

/**
 * @brief Function for handling data from temperature sensor.
 *
 * @param[in] temp          Temperature in Celsius degrees read from sensor.
 */
__STATIC_INLINE void data_handler(uint8_t temp)
{
    NRF_LOG_INFO("Value: 0x%x .", temp);
}

/**
 * @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_RX)
            {
                data_handler(m_sample);
            }
            m_xfer_done = true;
            break;
        default:
            break;
    }
}

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

    const nrf_drv_twi_config_t twi_lm75b_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_lm75b_config, twi_handler, NULL);
    APP_ERROR_CHECK(err_code);

    nrf_drv_twi_enable(&m_twi);
}

void HTU21D_sensor_init()
{
		//reset sensor
		ret_code_t err_code;
		m_xfer_done=false;
    uint8_t reg[1] = {0xfe};
    err_code = nrf_drv_twi_tx(&m_twi, HTU21D_SlaveAddress, reg, sizeof(reg), false);
    APP_ERROR_CHECK(err_code);
    while (m_xfer_done == false);
}

void read_data_reg(uint8_t regAddr)
{
		ret_code_t err_code;
		uint8_t reg[1] = {regAddr};
    m_xfer_done = false;
    err_code = nrf_drv_twi_tx(&m_twi, HTU21D_SlaveAddress, reg, 1, false);
    APP_ERROR_CHECK(err_code);
    while (m_xfer_done == false);
		
		m_xfer_done = false;
    /* Read 1 byte from the specified address - skip 3 bits dedicated for fractional part of temperature. */
    err_code = nrf_drv_twi_rx(&m_twi, HTU21D_SlaveAddress, &m_sample, sizeof(m_sample));
    APP_ERROR_CHECK(err_code);
		
}

int main(void)
{
    APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
    NRF_LOG_DEFAULT_BACKENDS_INIT();

    NRF_LOG_INFO("\r\nTWI sensor example started.");
    NRF_LOG_FLUSH();
	
    twi_init();
		HTU21D_sensor_init();
		read_data_reg(0xE7);  //read user register
		
    while (true)
    {
        nrf_delay_ms(500);
				
				read_data_reg(0xE3);  //read Temperature  register LSB
				read_data_reg(0xE3+1);  //read Temperature  register MSB
			
				NRF_LOG_FLUSH();
    }
}

/** @} */

Below is the log file

<info> app: Value: 0x2 .
<error> app: ERROR 17 [NRF_ERROR_BUSY] at ..\..\..\main.c:110
PC at: 0x000021A5
<error> app: End of error report

I sincerely look forward to your reply. thanks

RE: twi can't read data from sensor

haakonsh — Thu, 19 Mar 2020 14:13:38 GMT

We need a scope from a digital analyzer in order to know what's going on.

The holding/delay seems to be controlled by the slave, not the master.