TWI and BLE on nRF52840 DK

[gauthamranganathan]

Hello, 

I am interfacing nRF52840 DK with the MAX30101 sensor. I am able to execute all the TWI transactions necessary by using port 0 pin 27 as SCL and port 0 pin 26 as SDA. 

However when i use port 0 pin 14 as SCL and port 0 pin 13 as SDA I am not getting any output. I used ble_app_uart example and added TWI drivers. Are pins 14 and 13 assigned to something else in the ble_app_uart example? 

Changing pins is not an option, please tell me how I can go about working TWI on these pins. 

Thank you. 

[Mttrinh]

You should be able to do that if you don't initialize the buttons and lEDs. Remove buttons_leds_init(&erase_bonds) from main.

[Muhammad Nabeel]

Hi Gautham,

I am working on similar boards, I have configured the sensor correctly but when I read FIFO I get zero. Can you help me out with configurations?

[gauthamranganathan]

Hi Muhammad, 
Sure, i can help you. can you tell me your configuration values?

[Muhammad Nabeel]

/**@brief Function for initializations of max30101 .
 *
 * @param[in] p_instance  TWI instance.
*/
void setup(nrf_drv_twi_t const * p_instance)
{
	 
		//Setting the Mode configuration register
		regwrite8(p_instance,MAX30101_MODECONFIG, MAX30101_MODE_MULTILED); // Setting the mode to Multi LED i-e 0x07

	   // Multi Led mode control configuration register setup for slotx
    regwrite8(p_instance,MAX30101_MULTILEDCONFIG1,MULTI_LED_1); // Register 0x11 setup to value 0x21
	
		regwrite8(p_instance,MAX30101_MULTILEDCONFIG2,MULTI_LED_3); // Register 0x12 setup to value 0x03
	
		//LED Pulse applitude register to set the current in the led	
		regwrite8(p_instance,MAX30101_LED1_PULSEAMP,powerLevel); // Current register setup to value 0x1F
		regwrite8(p_instance,MAX30101_LED2_PULSEAMP,powerLevel);
		regwrite8(p_instance,MAX30101_LED3_PULSEAMP,powerLevel);


  
 // Configuration register setting
	/*
	*	Fifo roll over enabled
	*	Fifo sample average to 4
	*	Generate Interrupt when 29 samples are filled in memeory
	*/
		regwrite8(p_instance,MAX30101_FIFOCONFIG,MAX30101_CONF_FIFO);// Fifo configuration register setup
	
		// Spo2 Configuration setup 
		/*
		*	ADC range set to 4096
		* Sample Rate 400
		*	LED pulse width 411
		*/
		regwrite8(p_instance,MAX30101_PARTICLECONFIG,0x2F);
		// Clear fifo
		clearFIFO(p_instance);
	
}

/**@brief Function for writing the data to max30101 .
 *
 * @param[in] p_instance  TWI instance.
 * @param[in] RegAddr     Register Address to be written.
 * @param[in] data        Data to be written to the register.
 */
void regwrite8(nrf_drv_twi_t const * p_instance, uint8_t RegAddr, uint8_t data)
{
	uint8_t reg[2] = {RegAddr, data};
	nrf_drv_twi_tx(p_instance, MAX30101_ADDRESS, reg, sizeof(reg), false); //Repeated start is disabled
	nrf_delay_ms(5);
}

Code to Initialize the sensor

[Muhammad Nabeel]

Functions that I have used to get data from FIFO are following

/**@brief Function for reading the MAX30101_FIFOREADPTR register .
 *
 * @param[in] p_instance  TWI instance.
*/
uint8_t getRDptr(nrf_drv_twi_t const * p_instance)
{
	uint8_t data;
	regread8(p_instance,MAX30101_FIFOREADPTR,&data,true);
	return data;
}

/**@brief Function for reading the MAX30101_FIFOWRITEPTR register .
 *
 * @param[in] p_instance  TWI instance.
*/
uint8_t getWRptr(nrf_drv_twi_t const * p_instance)
{
	uint8_t data;
	regread8(p_instance,MAX30101_FIFOWRITEPTR,&data,true);
	return data;
}

/**@brief Function for reading the data from FIFO buffer .
 *
 * @param[in] p_instance  TWI instance.
*/
uint8_t *getdata(nrf_drv_twi_t const * p_instance)
{
	uint8_t wrptr=0;
	uint8_t rdptr=0;
	uint8_t scount=0; //Number of samples to be read from the sensor
	static uint8_t data[3];
	wrptr= getWRptr(p_instance); // FIFO_WR pointer 
	rdptr= getRDptr(p_instance); // FIFO_RD pointer
	scount =wrptr-rdptr;
	if(scount<0)scount+=32;
	nrf_drv_twi_tx(p_instance, MAX30101_ADDRESS, &MAX30101_FIFODATA, sizeof(MAX30101_FIFODATA), true);
	nrf_delay_ms(1);
	for(int i=0; i<scount;i++)
	{
		nrf_drv_twi_rx(p_instance, MAX30101_ADDRESS, &data[2], 1/*Read only 1 byte*/);
		nrf_delay_ms(1);
		nrf_drv_twi_rx(p_instance, MAX30101_ADDRESS, &data[1], 1);
		nrf_delay_ms(1);
		nrf_drv_twi_rx(p_instance, MAX30101_ADDRESS, &data[0], 1);
		nrf_delay_ms(1);
	}
	
	return data;
}