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73 lines
2.0 KiB
Plaintext
73 lines
2.0 KiB
Plaintext
= Raspberry Pi camera/LED demo
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== Overview
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The link:/[demo] consists of web app providing access to a webcam and a LED attached to a RaspberryPi.
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The device is assumed to have a limited bandwidth towards the server hosting the web app.
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== Objective
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The demo shows how to use websockets to communicate bidirectionally with an embedded device using standard protocols.
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It also shows that it's possible to use Smart.c to develop also the cloud endpoint and expose WebSocket and RESTful APIs
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easy to integreate with modern web stacks.
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== How it works
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image::docs/arch.png[]
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There are two components, once with runs on the device (`device_side`) and one that runs on a stronger machine
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and with more bandwidth (`cloud_side`).
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The device app connects to the cloud app via websocket and sends a new jpeg frame as fast as the underlying `raspistill` camera
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grabbing application can handle. The device automatically attempts reconnecting.
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The cloud side serves the webapp static pages and serves an MPJEG image on `/mpjg`.
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The MPJEG image handler blocks all the clients until a JPEG frame arrives via websocket
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and then every client will receive a copy of the frame.
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The web app can turn on and off the LED via a RESTful api accessible via the `/api` handler.
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== Installation
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=== Server side
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----
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git clone https://github.com/cesanta/mongoose
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cd mongoose/examples/web_demo
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make cloud_side && ./cloud_side 0.0.0.0:8080
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----
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=== Raspberry Pi
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The instructions provided here are tailored for the Raspbian distribution.
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==== Dependencies
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jpegoptim::
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apt-get install jpegoptim
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camera::
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run raspi-config and enable camera
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==== LED
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In order to access the led on your link:http://www.qdh.org.uk/wordpress/?page_id=15[HotPi]
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board you need to export the gpio pins:
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----
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for i in 22 23 24; do
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echo $i >/sys/class/gpio/export
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echo out >/sys/class/gpio/gpio$i/direction
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chgrp pi /sys/class/gpio/gpio$i/value
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done
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----
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==== Build and run
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----
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git clone https://github.com/cesanta/mongoose
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cd mongoose/examples/web_demo
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make device_side && ./device_side yourserver:8080
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----
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