nRF51 MPU9255 TWI/I2C READ Failed

RE: nRF51 MPU9255 TWI/I2C READ Failed

Nilesh — Mon, 04 Dec 2017 12:46:58 GMT

Yes, you are right. It was hardware isuue. I tried different MPU module. Now I am getting accelerometer values. Thanks a lot! Now I am trying nrf5-ble-mpu-simple. I want to see Accelerometer data on mobile. I am trying to connect nRF Toolbox. Can you please advice me where to observe data over BLE?

RE: nRF51 MPU9255 TWI/I2C READ Failed

dkwill — Mon, 04 Dec 2017 11:57:29 GMT

If you have addressed all the issues I noted above, it should generate output. If not, it is likely a hardware issue. You might try a different Mpu module if all else fails.

RE: nRF51 MPU9255 TWI/I2C READ Failed

Nilesh — Mon, 04 Dec 2017 06:43:20 GMT

Hi, I am using nRF52DK board (PCA10040). I changed all pins SDA,SCL pins as per boards in example. I connected MPU-92/65 to nRD52DK using 4 pins - GND, VDD, SCL, SDA. I am using Putty to observe output.
I am getting only output as ---- MPU nRF52 EasyDMA

Please help to get output.

RE: nRF51 MPU9255 TWI/I2C READ Failed

Vala — Tue, 11 Apr 2017 07:23:40 GMT

makerTim, there must be pull-ups on the TWI lines, either internal or external. I always prefer to have external resistors so I can choose the right value for them (for the maximum possible frequency depending on the capacitance of the lines). Decrease the frequency to 100K for the start just in case that the capacitance of the lines are large. You can do it in initializing the TWI module by nrf_drv_twi_init. And as dkwill pointed out, AD0 pin of MPU defines its TWI address which is very important. If this address is not right there won't be any response from the slave device (here MPU), which I guess causes timout. You can either change the configuration of this pin in hardware or simply modify that line of code that defines the slave device.

RE: nRF51 MPU9255 TWI/I2C READ Failed

dkwill — Tue, 11 Apr 2017 02:53:41 GMT

The AD0 defines the address - low is 0x68 which is in the example code. Mine has to be wired to GND for it to work. Just FYI - I had difficulty getting some of the 3rd party MPU boards to work and had to make my own board. Anyway, I think the answer for you is likely on the hardware side.

RE: nRF51 MPU9255 TWI/I2C READ Failed

makerTim — Tue, 11 Apr 2017 00:53:20 GMT

I wrote codes to read who Am I register, and its error code was 17.(busy, timeout) Maybe I should pull up 10K for TWI pins. By the way, what is ADO and why should I set it low?

RE: nRF51 MPU9255 TWI/I2C READ Failed

dkwill — Mon, 10 Apr 2017 22:04:38 GMT

I have gotten those examples working - nRF52 (with the exception of the magnetometer). I just changed the defines in the C/C++ tab and the TWI pins. Make sure to run in SDK 11.0. ADO should be set low for these examples. I used pullups of 10K. They should run w/ no major modification.

RE: nRF51 MPU9255 TWI/I2C READ Failed

Vala — Mon, 10 Apr 2017 12:46:48 GMT

Hi MakerTim,

I haven't used that code but I have implemented a library for communicating with MPU9250. If you provide more information someone might be able to help. How it doesn't work exactly? First try to read the WHO AM I register to see if the communication works OK. The value for MPU9250 should be 0x71. Then you can start initializing the sensor.