Use internal nRF52 pull-up w/ TWIM?

Question

Hi all -- 
 I have a tricky layout "issue" where unfortunately, I've ended up connecting my I2C device to the BlueTooth module on the side of the module where my VDD isn't routed (two-layer board + a solid GND plane on the bottom layer == tricky layout / using 0R resistors to jump traces...). 
 I have a set of 10K PU in my schematic right now to VDD -- on some parts I've used in the past, the PU/PD functionality of a given pin is tied to the GPIO 'peripheral' usage -- i.e., if that pin is given to a SPI/I2C or other peripheral, the pull-up / pull-down control is lost. 
 I expect that the internal PU is slightly weaker than 10k, but I only have a single I2C device on the board. Can I configure a pin to have the internal pull-up on in addition to being the TWIM SCL and SDA pins?

bjorn-spockeli · Accepted Answer

Hi Krunal, the internal pull-ups are enabled by default by the TWI Driver(nrf_drv_twi.c). If you take a look at the nrf_drv_twi_init(...) function you'll see that the GPIO pins are configured the following way NRF_GPIO->PIN_CNF[p_config->scl] = SCL_PIN_INIT_CONF; NRF_GPIO->PIN_CNF[p_config->sda] = SDA_PIN_INIT_CONF; where SCL_PIN_INIT_CONF and SDA_PIN_INIT_CONF are defined as #define SCL_PIN_INIT_CONF ( (GPIO_PIN_CNF_SENSE_Disabled << GPIO_PIN_CNF_SENSE_Pos) \ | (GPIO_PIN_CNF_DRIVE_S0D1 << GPIO_PIN_CNF_DRIVE_Pos) \ | (GPIO_PIN_CNF_PULL_Pullup << GPIO_PIN_CNF_PULL_Pos) \ | (GPIO_PIN_CNF_INPUT_Connect << GPIO_PIN_CNF_INPUT_Pos) \ | (GPIO_PIN_CNF_DIR_Input << GPIO_PIN_CNF_DIR_Pos)) #define SDA_PIN_INIT_CONF SCL_PIN_INIT_CONF Best regards Bjørn

Use internal nRF52 pull-up w/ TWIM?

Top Replies