RE: TWI Errata 89 workaround

YaroslavRakhnenko — Wed, 30 Mar 2022 07:33:08 GMT

void MLC_int_pin_handler(nrf_drv_gpiote_pin_t pin, nrf_gpiote_polarity_t action)
{
	i2c_init(); //Because the system in low power

	nrf_drv_gpiote_out_toggle(MLC_INT_LED);
	
	uint8_t MLC[8]={0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00};
	lsm6dsox_mlc_out_get(&dev_ctx, MLC);
	
	/* When putting the system in low power and the peripheral is not needed, 
	lowest possible power consumption is achieved by stopping, and then disabling the peripheral. */
	nrf_drv_twi_disable( &m_twi );
	nrf_drv_twi_uninit( &m_twi );
	
	/* Nordic work around to prevent burning excess power due to chip errata
	   Use 0x40003FFC for TWI0 */
	*(volatile uint32_t *)0x40003FFC = 0;
	*(volatile uint32_t *)0x40003FFC;
	*(volatile uint32_t *)0x40003FFC = 1;
}

...

/**
 * @brief	Function for i2c bus init.
 *
 * @param	none
 *
 */
void i2c_init()
{
  ret_code_t err_code;

  const nrf_drv_twi_config_t twi_config = {.scl                 = TWI_SCL_PIN,
                                            .sda                = TWI_SDA_PIN,
                                            .frequency          = (nrf_drv_twi_frequency_t)NRF_TWI_FREQ_400K,
                                            .interrupt_priority = APP_IRQ_PRIORITY_LOW,
                                            .clear_bus_init     = true};
  err_code                               = nrf_drv_twi_init(&m_twi, &twi_config, NULL, NULL);
  APP_ERROR_CHECK(err_code);
																	
	nrf_drv_twi_enable(&m_twi);
}

...


/**
 * @brief Function for application main entry.
 */
int main(void)
{
    ...
	
	gpio_init();
	i2c_init();

	/*
	*	Initialize mems driver interface
	*/
	dev_ctx.write_reg = i2c_LSM6DSOX_write;
	dev_ctx.read_reg 	= i2c_LSM6DSOX_read;
    dev_ctx.handle = NULL;

	/* Check device ID */
	static uint8_t whoamI=0, rst=0;
    lsm6dsox_device_id_get(&dev_ctx, &whoamI);
  		    		  	
	if (whoamI == LSM6DSOX_ID) 
	{
		 //Restore default configuration
		int ttl = 8;
		lsm6dsox_reset_set(&dev_ctx, PROPERTY_ENABLE);
		do {
			lsm6dsox_reset_get(&dev_ctx, &rst);
			if ((ttl-- < 0) && rst) {
				return 1;
			}
		} while (rst);
  		  		
		...
		
		/* Nordic work around to prevent burning excess power due to chip errata
			 Use 0x40003FFC for TWI0 */
		*(volatile uint32_t *)0x40003FFC = 0;
		*(volatile uint32_t *)0x40003FFC;
		*(volatile uint32_t *)0x40003FFC = 1;
	}
	else
	{
		return 1;
	}
	
	for (;;)
	{
		idle_state_handle();
	}
}

Thanks! Finally done!

I will post the final code here (parts that I changed regarding my post), maybe it will come in handy for someone!

RE: TWI Errata 89 workaround

Kenneth — Tue, 29 Mar 2022 11:40:45 GMT

Hello,

You can find that there is a Low Power chapter when using the TWI in the product specification:
https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/twim.html#concept_twi_low_power

So after executing a twi transfer, you should always disable the twi until next transaction. Before each twi transfer you can enable the twi and start twi transfer. The only difference due to the Errata 89, is that you need to execute the lines specified in Errata 89 after disabling the twi transfer.

I assume in your case you will need to add twi init and twi start transfer in LSM6DSOX_int_pin_handler(). And in the twi callback handler you need to disable and call Errata 89 if no additional twi is needed until next LSM6DSOX_int_pin_handler().

Kenneth