This is a personal project. I wanted to discover Asp.net Core 2.1 and SignalR.
I use a Raspberry pi 3 with an external board so I can easily plug cables and play with leds and buttons on GPIOs.
Here is the goal : count on an input (Gpio 17) linked to a photo-electric cell the number of passage of a fake fabric bottle line, simulated here by one propal of an old usb fan. The signal is read on Gpio17 by the raspberry pi and sent via SignalR to a web client (which is also host on the same raspberry pi server, with asp.net core razor pages.)
So I can read the counter on my web page in real time (almost).
GIT source code : https://github.com/couscousbzh/Nadine
Youtube Demo here : https://youtu.be/c3wAWcoAf0M
What you need
- A Raspberry pi 3 + power
- A testing board + cables (https://www.amazon.fr/gp/product/B01I58Y766/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1)
- A case (optional https://www.amazon.fr/gp/product/B01KZ26LKA/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1)
- A SSH client (putty or mobaXTerm)
- A button (I use a little button on board and a eletric photo cell, but I guess you don’t have one…)
- Some cables
How it works
In Asp.net Core you can manage WebHost as usual (your web site) but you can add other host that can act like a service.
This is what i’ve done. I create two services, webhost and a timehostedservice. If my english is not so bad, I understood that host and webhost services will be « Generic Host » in the future. So I guess this will change in the future. I notice some diffences when creating it. With webhost service you can configure it in one line (CreateDefaultBuilder) but there is no such thing for host. Anyway, all of this is coded in program.cs and startup.cs (this one is basically only used for webhost)
Timehost is a loop, you set the frequence you’d like. I set a 1 ms loop. So every 1ms, I call a worker to do a job. Which is basically just to read Gpio 17 input state.
I start the webhost first and then the timehost.
Webhost takes time to launch. And if counting starts, it needs to connect to Hub and do a start connexion first. But if the webhost is not yet started, I have an error. So I delay the worker init to 10s. I know this is ugly, this is something I wanted to correct but I spent too much time. And by the way, i am not sure that running 2 services like that is the best solution. Maybe doing 2 separate projects with their own life is better. So I did not loose my time on this.
Web Service (host)
Basic project made with a « dotnet new webapp » cli command.
Then I follow the microsoft guide line : https://docs.microsoft.com/fr-fr/aspnet/core/signalr/introduction?view=aspnetcore-2.1
this give me a little chat room exemple using SignalR.
Then, I add a Counter Page. The goal of this is to simulate a counter (like a bottle counter sensor) and upload the value directly in client web page, using SignalR.
Template Gentelella : https://github.com/puikinsh/gentelella
npm init -y
npm install @aspnet/signalr
npm install gentelella –save
WARNING : all of my code use hard IP adresse 192.168.8.123, please change it to yours or add a dynamic system.
GPIOs Service (host)
Thanks to Jeremy Lindsay, I could use the GPIOs as I wanted. Here is some usefull links :
I copy some classes into /GpioManager folder.
And my code is basically located into the worker class (/HostedServices/Worker.cs)
Here is some usefull commands
For Raspbian Debian 9 Jessie you need to do the following (only once):
sudo apt-get update sudo apt-get install curl libunwind8 gettext apt-transport-https
chmod 755 ./MyWebApp
export ASPNETCORE_URLS= »http://*:5000″
export ASPNETCORE_URLS= »http://192.168.8.123:5000 »
WiringPi is a lib for linux (not C#) this can be helpfull to check input status or manually set them.
gpio mode 0 in (0 match GPIO 17)
gpio mode 2 in (2 match GPIO 27)
gpio mode 5 out (5 match GPIO 24)
Deploy Asp.net Core 2.1
On dev environnement :
dotnet publish -c Release -r linux-arm copy publish folder content to RapsberryPi
I wrote some powershell script that can helps to deploy in one command line.
.\ps-deploy-raspian.ps1 -ip 192.168.8.123 -destination « /home/pi/Dotnet/Nadine » -username pi