TWI problem, possibly voltage related

RE: TWI problem, possibly voltage related

John Buckley — Sun, 14 Jan 2018 17:26:51 GMT

Sorry for the slow response on this. It does appear that it is an issue with the level converters. We have a 3.3V development header board in production. Thanks.

RE: TWI problem, possibly voltage related

MartinBL — Wed, 03 Jan 2018 11:23:41 GMT

Maybe it is an issue with the voltage levels of the SDA and SCL lines. I guess there will be a voltage drop across the Logic Level Converter that might drop the voltage down below the nRF52's required Vih.

Bypassing the LLC seemed to be the solution for this guy.

An screenshot of the signals would definitely be useful, but maybe you can try to measure the signals with a simple multimeter when the TWI bus is idle.

RE: TWI problem, possibly voltage related

John Buckley — Mon, 01 Jan 2018 15:00:03 GMT

The TE MEAS MS5611 barometric sensor on a breakout board designed for 5v. See here - www.hobbytronics.co.uk/ms5611-altitude-sensor I have four of these and they all still work with an arduino, so they are not broken. The circuit works with a nrf5 when I attach a Bosch BMP280, so it does not seem to be a problem with the nrf5. I have also tried it on two different nrf52DK PCA10040, with the same result on both. So it does not seem to be a problem with any individual unit.

RE: TWI problem, possibly voltage related

Turbo J — Mon, 01 Jan 2018 14:05:58 GMT

MS5611 [...] 5V

The MS5611 chip is designed to work with 3.3 Volts. Its absolute maximum is 4.0V. If you connect those to a 5V source the expected result are broken sensors, period. Similar story with the NRF5x, by the way.

Note that modules made for 5V sytems should have the required 5V=>3.3V circuitry, and may not work quite properly on 3.3V only systems. But since OP did not provide a schematic this is only guesswork at this time.