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