To collect multiple sensor values and transmit it over bluetooth using nrf52840 DK

[sprasad]

Hello!

I'm looking to build an application on nrf52840 DK that collects multiple sensor values and transmits it over Bluetooth. For now, I don't have a bluetooth application of my own so it's enough if I'm able to read those values using nrf connect app. I'm planning to retrieve values from the onboard temperature sensor and two other sensors that are connected using i2c. I have gone through the posts and tutorials but I find that most of them aren't ported to nrf52840 board. Can anyone point me to right example/ tutorial/ blog that can help me achieve this on nrf52840?

[sprasad]

Currently, I'm looking into the ble_app_template. Just the connect and disconnect are working fine with my nrf connect iOS app on phone. From here how do I alter this to display sensor values on my phone? Should I have to begin with adding services?

[karthikeyan]

hi,

  which sdk you are using. and if you want to connect the sensor in i2c(twi). there is an example for twi. from there you can start.

regards

[karthikeyan]

hi,

  i have done mpu 6050 interfaced in twi using sdk 14.2 and got success. having that source code if you need i can give u

[sprasad]

That would be great! Can you please share it? Thanks a lot!!

[karthikeyan]

hi,

mpu.zip

if you have mpu 6050. just extract this go to example-->ble_peripheral-->ble_template. build it and load the file in your dk. no need to make any modifications. the output can be seen through uart and as well as in nrf_connect app. the 

twi_sda is p0.26

twi_scl is p0.27

the output of accel values will be displayed for every one sec. in nrf_connect app. connect the device go to services enable notification.

[sprasad]

Will look into it. Thanks again!

[Var]

Hi Karthikeyan,

1) I am trying out the above ble_ app_template code for a MPU9250 but I am confused as to how to go around including the drivers for it in the project explorer and also I tried compiling the file from the mpu.zip and it throws an error for the #include app_mpu.h in the main.c saying that no such file or directory found. I could not find the file. If this needs to be written then would you be kind enough to point me in a direction where I can start.

2) Could you also help me understand the SDK and how to go through it since there seem to be many folders with .h and .c files and which ones to use. Any general structure or procedure or even a nudge in the right direction would be helpful.

I am using Segger embedded studio and SDK 14.2.0 currently.

Thank you!!

[karthikeyan]

hi var,

 the mpu zip file i have posted will work out of box. in which compiler are you working with.

cheers

[Var]

Compiler that Embedded studio uses is by default GCC.

On compiling there is an error " app_mpu.h file cannot be found".

[karthikeyan]

hi var,

  there is app_mpu.h file in the zip file. you no need to write code by yourself. in your compiler you just add relative path for app_mpu.h file. 

cheers

karthikeyan

[sprasad]

Hey Var,

That header file which you are looking for is in

components/ble/ble_services/ble_mpu/

To build the example shared by Karthikeyan you can follow these steps:

Use Preprocessor->Preprocessor Definitions to define the following

• MPU9255
• MPU_USES_TWI

Include "components/ble/ble_services/ble_mpu" in Preprocessor->User Include Directories

Add drivers for twi and mpu twi in nRF_Drivers folder of the project

Add mpu files from ble_services/ble_mpu in ble folder of the project

Enable TWI in sdk_config.