Combining UART and MPU6050

[ThienVu]

Hello,

I was able to build the example project MPU6050 from Github with SDK 16. However, I used Putty to connect to the board (PCA10056) with baudrate of 115200 on COM3 (the COM Port it is connected to) but I didn't get any debug string. The sdk_config.h file I took directly from the example.

I used GPIO to turn on a LED when a value from the MPU changed, and the LED changed, verifying that the MPU is not faulty, and I setup the read data from the MPU right, just the UART part is incorrect.

May I get some help getting UART running? What to include in sdk_config.h? What function, c source file, header, do I need?

Thank you very much.

[Guojun Wang]

Hi,

You can take sdk_config.h in example "nRF5_SDK_16.0.0_98a08e2\examples\ble_peripheral\ble_app_blinky\pca10056\s140\" as reference and I am able to get uart logging after flashing both the softdevice hex and the application hex.

In the sdk_config.h, you need to make sure at least

#define NRF_LOG_BACKEND_UART_ENABLED 1
#define NRF_LOG_BACKEND_RTT_ENABLED  0

Regarding to the files needed, you can take a look of the above mentioned example. And please let us know if it still doesn't work. And it would be nice to upload your configuration for us to reproduce as well.

[ThienVu]

/cfs-file/__key/communityserver-discussions-components-files/4/mpu_5F00_project.zip

Hello,

Thank you for replying. I'm uploading the zip of my project. Currently I have to comment out all the printf() because for some reason they interfere with the GPIO.

This project is based on the peripheral template project from the SDK. I just modified the main.c and add the custom source files for MPU

The sdk_config.h is the one came with the example from Github here Github Example

Please unzip it in SDKFolder/examples/peripherals.

Thank you very much for helping.

[Guojun Wang]

Hi, 

The example you taken was from SDK 14.2. And there were some changes to logging since then.

There are two approaches you can take:

1. Update based on your current sdk_config
2. Port your project based on SDK 16 examples

Regarding to option 1, basically you need to set the following defines to get the uart logging

• Set NRF_LOG_ENABLED = 1 in sdk_config.h
• Copy in the NRF_LOG_BACKEND configuration from an example using UART backend, such as examples/ble_peripheral/ble_app_hrs

• // <e> NRF_LOG_BACKEND_UART_ENABLED - nrf_log_backend_uart - Log UART backend
  //==========================================================
  #ifndef NRF_LOG_BACKEND_UART_ENABLED
  #define NRF_LOG_BACKEND_UART_ENABLED 1
  #endif
  // <o> NRF_LOG_BACKEND_UART_TX_PIN - UART TX pin 
  #ifndef NRF_LOG_BACKEND_UART_TX_PIN
  #define NRF_LOG_BACKEND_UART_TX_PIN 6
  #endif
  
  // <o> NRF_LOG_BACKEND_UART_BAUDRATE  - Default Baudrate
   
  // <323584=> 1200 baud 
  // <643072=> 2400 baud 
  // <1290240=> 4800 baud 
  // <2576384=> 9600 baud 
  // <3862528=> 14400 baud 
  // <5152768=> 19200 baud 
  // <7716864=> 28800 baud 
  // <10289152=> 38400 baud 
  // <15400960=> 57600 baud 
  // <20615168=> 76800 baud 
  // <30801920=> 115200 baud 
  // <61865984=> 230400 baud 
  // <67108864=> 250000 baud 
  // <121634816=> 460800 baud 
  // <251658240=> 921600 baud 
  // <268435456=> 1000000 baud 
  
  #ifndef NRF_LOG_BACKEND_UART_BAUDRATE
  #define NRF_LOG_BACKEND_UART_BAUDRATE 30801920
  #endif
  
  // <o> NRF_LOG_BACKEND_UART_TEMP_BUFFER_SIZE - Size of buffer for partially processed strings. 
  // <i> Size of the buffer is a trade-off between RAM usage and processing.
  // <i> if buffer is smaller then strings will often be fragmented.
  // <i> It is recommended to use size which will fit typical log and only the
  // <i> longer one will be fragmented.
  
  #ifndef NRF_LOG_BACKEND_UART_TEMP_BUFFER_SIZE
  #define NRF_LOG_BACKEND_UART_TEMP_BUFFER_SIZE 64
  #endif
  
  // </e>

• Optionally, change NRF_LOG_DEFERRED to 0 if you don't need deferred logging (when using deferred logging you need to run NRF_LOG_FLUSH() in the main loop to get any log output). 
• Use NRF_LOG_XXX for logging purpose.

 I am able to get logging work with above changes. 

[ThienVu]

Thank you very much. I got it working now.

[ThienVu]

Just a quick question. I would like to: On first power on, wait for a button push. Then after it is pushed, go to a "calibration" period and then go to main loop. Also if the button is pushed again, the system goes to "calibration" period and then back to main loop. How can I structure that?

[Guojun Wang]

Hi, 

I recommend you open another ticket for this question, to keep this ticket specific for logging related discussions and easy for others to follow as well.