meta-ppgInteraction

Yocto BSP layer developed for interacting with a ppg sensor and giving the user his hearth rate (CDD + APP recipes).

The physical sensor has been simulated by sampling, instead of the real hardware device, the data present in the data.h file.

Target machine

Raspberry pi 4
(see compatibility note at the end (*))

Content

app_recipe
cdd_recipe
(respectively to implement the application interface and the sensor device driver).

Use

To launch the application, just run this command:

hearthmonitor

Patches

Please submit any patches against the meta-ppgInteraction layer through the github issue section of this repository.

Maintainer: https://github.com/alessandrolandra

Adding the meta-ppgInteraction layer to your build

The following instructions are supposed to be executed in a Linux environment equipped with Poky, as reference distribution of the Yocto Project.

First of all you need to clone this repository (or download and copy the whole meta-ppgInteraction directory) into your poky folder.
Then, after initializing your environment with source oe-init-build-env <your_build_path>, you have to add this layer to the image configuration by running:

bitbake-layers add-layer <your_poky_folder>/meta-ppgInteraction/

(In alternative you can add a line in <your_build_path>/conf/bblayers.conf file, reporting <your_poky_folder>/meta-ppgInteraction \ inside the BBLAYERS string).

Finally, to add the newly created recipes to the image to be deployed, you have to edit <your_build_path>/conf/local.conf file by adding the following lines:

IMAGE_INSTALL_append = " hearthmonitor ppgreader"
KERNEL_MODULE_AUTOLOAD += "ppgreader"

You can now build the new image.
If you are using a console only version, like the one that I used, the needed command is:

bitbake console-image

(*) This layer may probably also work on other architectures (other raspberry pi model, qemu etc), but probably some timing differencies must be taken into account in the app_recipe.
I succeeded in making this work with the qemuarm machine architecture;
all you need to do, in order to make these recepies compatible, is to change the COMPATIBLE_MACHINE in meta-ppgInteraction/recipes-ppg/cdd_recipe/ppgreader.bb (I didn't add both machines because my target is only the raspberry pi 4):

COMPATIBLE_MACHINE = "qemuarm"

The timing change that I was mentioning before, for my qemuarm machine, was to decrease the sleep interval in line 64 of the meta-ppgInteraction/recipes-ppg/app_recipe/files/hearthmonitor.c file from this usleep(20000) to something like usleep(16000), due to the limited resources and poor timing precision of my emulator.