Reading from Analog > Digital

[nick-jonas]

I'm trying to read data from 2x10k potentiometers that are wired to the 1st two inputs of an MCP3008, and then the MCP3008 is hooked up to the RPi like this:

(rpi on the left, mcp3008 on the right):

Pin 19 (MOSI / #10) -> pin 11 (Din)
Pin 21 (MISO / #9) -> pin 12 (Dout)
Pin 23 (SCKL / #11) -> pin 13 (CLK)
Pin 24 (CD0 / #8) -> pin 10 (CS)
Pin 6 (GND) -> pin 14 (AGND) & 9 (DGND)

How do I go about doing this? The only reference code I could find on johnny-five is for the Grove shield and Edison board:

var rotary = new five.Sensor("A0");

rotary.scale(0, 255).on("change", function() {
    // do stuff with this.value
});

How do I create two rotary instances (what would I use for the GPIO pins)?

[fivdi]

The MCP3008 is an SPI device but Johnny-Five and Raspi-IO currently don't support SPI devices. What should work is the PCF8591 which is an I2C device. I2C is supported. See http://johnny-five.io/examples/expander-PCF8591/

[fivdi]

See also rwaldron/io-plugins#3

[nick-jonas]

Hmm tried using node-spi from @RussTheAerialist as mentioned in that thread but getting issues on the install with node-gyp:

russtheaerialist-retired-projects/node-spi#25

I'll order a PCF8591, and if there are any other ideas of things to try with the MCP3008, let me know - thanks!!

[fivdi]

@nick-jonas what version of Node.js are you using? https://github.com/RussTheAerialist/node-spi supports v0.10 and v0.12, but not v4 or higher

[nick-jonas]

@fivdi v0.10.36

[nebrius]

Hi @nick-jonas! Just so you're aware, using node-spi and this SPI device won't make the analog data available to Johnny-Five. You can certainly still use it, but you'll have to parse the SPI data yourself, and wire up your own event logic independent of Johnny-Five :(

If at all possible, I'd recommend going with the I2C backpack that @fivdi mentioned.

[nebrius]

I believe the issue was addressed in the previous comments. If there is still an issue that needs to be fixed, feel free to reopen.