Can't find twi / i2c MS5611 device with nRF52840

RE: Can't find twi / i2c MS5611 device with nRF52840

ovrebekk — Mon, 08 Jul 2019 07:53:28 GMT

Thanks for sharing the analog plot. Based on that it doesn't appear to be a signaling problem, the sensor simply doesn't ack the command for some reason.

Have you made sure that the CSB pin is the same in both cases, to satisfy the requirement from the sensor datasheet that the MS5611-01BA address is 111011Cx, where C is the complementary value of the pin CSB?

The working example based on the Adafruit Trinket is issuing a write command, while the non working example with the nRF52840 is issuing a read command. Can you try a write command on the the nRF52840 also and see if it still doesn't work?

Best regards
Torbjørn

RE: Can't find twi / i2c MS5611 device with nRF52840

MirkoB — Fri, 05 Jul 2019 15:13:42 GMT

Below the full view of the nRF52840 communication including analog signal. And yes, there are 4.7k pull ups on the board.

RE: Can't find twi / i2c MS5611 device with nRF52840

awneil — Fri, 05 Jul 2019 15:04:57 GMT

[quote userid="2116" url="~/f/nordic-q-a/49398/can-t-find-twi-i2c-ms5611-device-with-nrf52840/196863"]the digital plot doesn't show the full picture[/quote]

RE: Can't find twi / i2c MS5611 device with nRF52840

ovrebekk — Fri, 05 Jul 2019 13:46:54 GMT

Those results are a bit odd.

The nRF52840 seems to introduce more delays, but that should be OK. There is also something looking like a glitch on the clock line, which might be more problematic.

Are you able to measure the lines with an analog probe?

Some times the digital plot doesn't show the full picture.

Do you have external pull ups on the lines?

Best regards
Torbjørn