nRF52-DK / TWI does not send anything

RE: nRF52-DK / TWI does not send anything

Sami — Thu, 12 Mar 2020 09:50:23 GMT

This is indeed a sensor issue. I have tested the source code with another sensor and it sends an ACK successfully.

RE: nRF52-DK / TWI does not send anything

Sami — Wed, 11 Mar 2020 10:24:28 GMT

It seems that the problem was caused by too long wires. I tested with really short wires and the I2C bus became active.

However, there is still another problem. It seems that the hold time is very short, only about 0.5us. As a consequence, the sensor does not read the address correctly and it does not send an acknowledge. I tested the sensor with another MCU and the sensor worked fine. In this case, the hold time was about 2.5us.

However, it seems that the issue is more related to the sensor than the MCU, because the I2C standard indeed indicates that the SDA must remain stable only when the SCL is high. I would still like to check if it is possible to adjust the TWI in any way to solve this issue.

RE: nRF52-DK / TWI does not send anything

Sami — Tue, 10 Mar 2020 12:36:06 GMT

I have also tested to set the pins manually in the beginning of i2c_init(). I have tried both with and without internal pullup resistors. The board has been connected to a digital temperature sensor (I2C). The temperature sensor has also pullup resistors (10K).

nrf_gpio_cfg_input(I2C_SCL_PIN,NRF_GPIO_PIN_PULLUP);
nrf_gpio_cfg_input(I2C_SDA_PIN,NRF_GPIO_PIN_PULLUP);

nrf_gpio_cfg_input(I2C_SCL_PIN,NRF_GPIO_PIN_NOPULL); 
nrf_gpio_cfg_input(I2C_SDA_PIN,NRF_GPIO_PIN_NOPULL);