twi_scanner example only returning address 0x01

[CraigE]

I have set up a custom board using the nRF52811 based BMD-360 module.

I have tested the twi_scanner example, first of the nrf52DK with an external sensor. I Changed the TWI pins to the ones I am using on the custom board (SCL: 26, SDA: 25) and verified it worked as expected returning the address of the sensor over UART.

I have set up a custom board using the nRF52811 based BMD-360 module, and modified the project to target the nrf52811 (extracted settings from a PCA10056e project and changed the target, etc.). The program compiles fine and runs. My custom board doesn't have a serial output, so I have placed breakpoints to check for any detected devices. 

I only seem to be detecting one device on address 0x01, regardless of if I have a sensor attached to the board or not. I have tried the same sensor as I used with the DK connected, and still get the same result.

I have pull-ups on the TWI lines and nothing else on the bus so I don't think it's a hardware issue. I think it may just be a configuration problem moving from the nRF52840 DK to the nRF52811?

Any help would be appreciated.

(Using nRF5 SDK16.0.0)

[Marjeris Romero]

Hi,

First, you can make sure you have followed all the steps in the "Transferring the project to nRF52811 hardware" guide on the infocenter.

Could it be that you are using the wrong pins? You can double check which pins you are using looking at the TWI register. Check the PSEL.SCL and PSEL.SDA pin registers:

If you have a logic analyzer or oscilloscope at hand you can also look at the traces to see how the signal looks like.

Best regards,

Marjeris

[CraigE]

@msromero, Still no luck getting this to work, but I am seeing I2C waveforms on the scope on the correct pins.

This returns a device found at address 0x01 for some reason:

It looks like when I address the LSM303DLHC sensor I'm using to test it does provide a I2C response:

For whatever reason it's not picking this up in software. Any ideas?

[CraigE]

Hi, still waiting on help with this.

[Marjeris Romero]

Hi,

Sorry for the late reply. When SDA remains HIGH during the ninth clock pulse, the signal is defined as a NACK. But you say you are reading it as being a device found at address 0x01? Can you explain more about how you are checking the result?

BR,

Marjeris

[CraigE]

Yes,I I'm confused by this too. The fact it completely ignored an ACK response from the device doesn't make sense.

  I'm using the twi_scanner example straight out of the box, other than making the changes shown above to port it to the 52811. Since this works on the nrf52 DK possibly it's something to do with the porting process? I'm using a module (bmd360) but judging by the i2c waveforms that's still all working as expected.

[Marjeris Romero]

Can you explain how you are checking the results? You said that you didn't implement logging, so are you checking with running the example in debug or something? I suspect something can be going wrong here...

My custom board doesn't have a serial output, so I have placed breakpoints to check for any detected devices. 

 BR,

Marjeris

[CraigE]

I was setting breakpoints at the appropriate points in the code and examined the address variable. This worked fine on the nRF52 DK.

I now enabled RTT logging to check it. Though sometimes it looks like it might detect the I2C device, the output from is completely unreliable so debugging if it actually works is still near impossible. I've attached my project if you'd like to examine it.

It should be such a simple task to communicate with an I2C device, but even the examples barely seem to work out of the box after a minor port to another supported part. It's very frustrating for me.

2772.twi_scanner.zip

[Marjeris Romero]

Hi Craig,

Sorry for the late reply. Could you also attach the schematics of you custom board?

How are you powering the TWI device and how is it connected to the nRF chip?

Can you also attach the output from the RTT log?

BR,

Marjeris