a-tortevois/widgetlords-pi-spi-8ai

A simple TCP socket server in C with a Websocket Client/Server in Node.JS and a final client in HTML/Javascript for Widgetlords Pi-SPi-8AI boards

Getting Started

• Stack Architecture
• RPi hardware configuration (for MCP3008)
• Software installation

Stack Architecture

This stack is composed with :

• ADC Monitor provide an API to get all input values for Widgetlords Pi-SPi-8AI boards with MCP3008 chip. Monitor is written in C, with two tasks:
  • A reading loop to update internally all inputs values,
  • A TCP socket API server available on port 3000 to expose all inputs values in JSON for external service,
• A basic WebSocket Gateway available on port 8888, written in JavaScript and runnable with node.JS,
• A lightweight Web Server, with only one page to expose the HTML/Javascript and WebSocket Client interface.

The TCP socket API server accepts only one client: the WebSocket Gateway which more easily provides multi-client mode.
The API provide only two methods:

• get/all to get all values:

Query	Response
{ "topic": "get/all", "payload": {} }	{ "status": 200, "timestamp": <timestamp> "payload": { "adc": { "i": [<index>], "v": [<value>] }, "io": { "i": [<index>], "v": [<value>] }, "sw_version": "<version>" } }

• set/out to enable an output:

Query	Response
{ "topic": "set/out", "payload": { "i": [<index>], "v": [<value>] } }	{ "status": 201, "timestamp": <timestamp> "payload": { "io": { "i": [<index>], "v": [<value>] }, } }

The field payload takes an object with the i and v fields, which are two arrays:

• Array i contains all the variables indexes
• Array v contains all the variables values

Once connected, the TCP socket API server automatically sends all (but only) updated inputs. Then, you have to associate the indexes with the values contained in the two arrays.

For io, for the moment, only 2 outputs are driven (see the mapping in adc-monitor/src/drivers/gpio.c):

• GPIO23 as O_KA1 with the index 0
• GPIO24 as O_KA2 with the index 1

RPi hardware configuration (for MCP3008)

1. Enable the SPI interface, with the command:

$ sudo raspi-config

Then, select Interface Options > SPI > Yes

2. Install the libwidgetlords package

$ wget https://github.com/widgetlords/libwidgetlords/releases/download/v2.1.1/libwidgetlords_2.1.1_arm64.deb
$ sudo dpkg -i libwidgetlords_2.1.1_arm64.deb

NOTE: If you have previously installed the library you must remove it first using

$ sudo apt remove libwidgetlords

For more information, see https://widgetlords.com/pages/getting-started-with-pi-spi-libraries

3. Edit the /boot/config.txt file add to dtoverlay:

dtoverlay=pi-spi:extra_cs=true

Then reboot your Raspberry

4. Check if the SPI devices are properly mounted with the command:

$ ls /dev | grep spidev

5. Address the chips

The four chip selects are shown here:

Only 1 jumper should be installed at a time.
Typically, the jumpers are installed as follows:

Jumper	Module	Interface	Address	JSON index
CE1	1	/dev/spidev0.1	ADC_DEV_0_CHAN_0 .. ADC_DEV_0_CHAN_7	0 .. 7
22	2	/dev/spidev0.4	ADC_DEV_1_CHAN_0 .. ADC_DEV_1_CHAN_7	8 .. 15
27	3	/dev/spidev0.5	ADC_DEV_2_CHAN_0 .. ADC_DEV_2_CHAN_7	16 .. 23
18	4	/dev/spidev0.6	ADC_DEV_3_CHAN_0 .. ADC_DEV_3_CHAN_7	24 .. 31

Software installation

Run the following commands:

$ git clone https://github.com/a-tortevois/widgetlords-pi-spi-8ai.git
$ cd widgetlords-pi-spi-8ai
$ chmod +x run.sh
$ ./run.sh --install
$ systemctl start adc_monitor.service
$ systemctl start adc_monitor_websocket_gateway.service
$ systemctl start adc_monitor_web_server.service
$ systemctl list-units --type=service | grep adc_monitor

Software update

Run the following commands:

$ cd widgetlords-pi-spi-8air
$ git fetch --all
$ git reset --hard
$ git pull --all
$ systemctl stop adc_monitor*
$ chmod +x run.sh
$ ./run.sh --install