MS8607 (PHT Click) sensor data over I2C and a driver on nRF52840 DongleReading

[ingridal]

Hello!

I have started building an IoT test node using nrf52840 Dongle and MicroE MS8607 (PHT Click) sensors (please see the setup below). The functionality we are interested in is reading the sensor data over i2c and sending it via UART to the PC. 

The whole solution will be realized under Zephyr RTOS, therefore i2c configuration needs to be adapted as per Zephyr official docs: I2C Zephyr Project Documentation ; Zephyr API for i2c Bus. 

At the current stage it will be at user space, using kernel functions, i2c and UART for serial communication. I am developing under Linux Ubuntu 22.04 LTS, using Sublime Editor for code writing, Linux console for building an app and CuteCom for serial communication testing. nRF Connect for Desktop and it's tools as well as VS Code IDE aren't used. 

Since I am pretty new into the embedded software development field (mostly did web-app programming), there are main things I am confused about:

• How to declare ic2 device combining nrf libraries, Zephyr packages and taking into account the manufacturer's recommended settings.
• What is an approach and key-points of writing a driver for this particular solution?
• The main confusion lays within where to start optimally as I am a bit with how to ensure all the compatibility as well as I haven't seen any sample solutions or demos for this sensor. 

* Native PHT Driver from manufacturer (MikroE):

pht.zip

Has anyone out here already worked with MS8607 (PHT Click) sensor on nRF52840 Dongle (PCA10059) through Zephyr RTOS?

Would appreciate any guidelines and approach. 

Thank you in advance!

p.s: Undoubtedly, it would be better to start with something more user clear (such as nRF52840 Development Kit or Arduino) but this time it is not an option, and I need to develop a solution using only the above mentioned hardware. 

Sincerely
Ingrid

Setup

Sensor Data sheet:
ENG_DS_MS8607-02BA01__C3.pdf

[haakonsh]

I suggest you drop MikroE's driver completely as it is written for a different system and rather use the manufacturer's. TE Connectivity has a generic driver: https://github.com/TEConnectivity/MS8607_Generic_C_Driver/blob/master/ms8607.c. 

For Zephyr integration:

The MS8607 contains two I2C slaves with different I2C addresses, so you might need to create 2 child nodes under the I2C bus node that you intend to use. 

I suggest that you study the drivers of other I2C sensors in zephyr and note how it uses the I2C drivers. F.ex zephyr\drivers\sensor\lis2dh\lis2dh_i2c.c 

Here's a typical I2C Devicetree node for an lis2dh12 sensor: 

&i2c1 {
	compatible = "nordic,nrf-twim";
	status = "okay";
	clock-frequency = <I2C_BITRATE_FAST>;

	pinctrl-0 = <&i2c1_default>;
	pinctrl-1 = <&i2c1_sleep>;
	pinctrl-names = "default", "sleep";
	lis2dh12: lis2dh12@19 {
		compatible = "st,lis2dh12", "st,lis2dh";
		reg = <0x19>;
		irq-gpios = <&gpio0 12 GPIO_ACTIVE_HIGH>;
	};
};

Note that most sensors in Zephyr uses a higher abstraction Sensor API on top of their drivers, and you will need to ignore that. Unless you want to use the Sensor API for your device, then you will need to write a Sensor driver implementation for the ms8607 as well. 

nRF Connect for Desktop and it's tools as well as VS Code IDE aren't used. 

I strongly advice you to use these tools, they exist for good reason.

p.s: Undoubtedly, it would be better to start with something more user clear (such as nRF52840 Development Kit or Arduino) but this time it is not an option, and I need to develop a solution using only the above mentioned hardware. 

If you don't have access to a compatible debugger (DK has one) you are setting yourself up for failure. 

[ingridal]

Dear haakonsh !
Thanks a lot for your valuable feedback and guidelines. How would you recommend to establish UART communication between the nRF52840 Dongle and the PC? One of the solutions I have found so far is using nrfx_uarte driver.  Maybe there are other options?

[haakonsh]

You need to set up a a virtual COM port, also known as USB CDC ACM. Various subsystems like Console, Shell, and Logger, can use the USB CDC ACM as a Serial backend, as opposed to a HW UART peripheral that the nrfx_uarte driver interfaces with.  

See f.ex. USB CDC ACM Sample Application and Console over CDC ACM UART Sample. 

[ingridal]

I will check them thank you. The overall approach is much more clearer now, and I will start working within the available resources. 

Referring to your comment about the lack of a compatible debugger makes me worry either - does not seem a good perspective for developing an efficient solution  but it is an issue to solve within our team. 

Really appreciate your time and consideration.