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node-red-nodes/hardware/mcp3008/README.md
2018-09-21 13:53:08 +01:00

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node-red-node-pi-mcp3008
========================
A <a href="http://nodered.org" target="_new">Node-RED</a> node to read from
the MCP3xxx Series of Analogue to Digital Converters,
such as the <a href="http://rasp.io/analogzero" target="_new">Rasp.io analogzero</a>, though it will work with breadboard versions also.
It will appear in the menu as ` A/D Converter `.
**Warning**: Input voltages must not exceed 3.3V
### Pre-requisites
You must ensure that SPI is enabled. For recent (2016) versions of Raspbian you can do this
- Run `sudo raspi-config`
- Select `5 - Interfacing Options`
- Select `P4 - SPI`
- Select `yes` to enable SPI
- Select `OK` to confirm
- Select the `Finish` button
### Install
Run the following command in your Node-RED user directory - typically `~/.node-red`
npm install node-red-node-pi-mcp3008
**Note**: It will appear in the menu as ` A/D Converter `.
### Usage
Reads from an MCP3xxx Analogue to Digital (ADC) chip on the Pi SPI connection.
You can either set a channel in the edit dialogue, or you can set the `msg.payload` to
select the channel dynamically. If so then the payload must be a value from 0 to 7.
You can also select device id 0 or 1 (CE0 or CE1) depending on how you have wired up your device. Defaults to CE0.
And you can also select the SPI bus number 0 or 1 depending on how you have wired up your device. Defaults to 0 for spidev0.
Outputs a numeric `msg.payload` with a range of 0 to 1023, where 0 = 0V and 1023 = 3.3V (assuming you use the default 3.3V voltage reference).
**Hint**: use a `range` node to adjust the values to the range you want.
Also sets `msg.topic` to `adc/{the pin number}`