How to use mcp3008 library in Node-RED on RPi?

Michael Doroshenko

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Oct 31, 2016, 3:36:43 PM10/31/16

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I have installed this library in my ~/.node-red directory:
https://www.npmjs.com/package/node-red-node-pi-mcp3008

However, even after I restart node-red and the pi, I still don't see the mcp3008 node on the left pane.
What am I doing wrong???

Zenofmud

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Oct 31, 2016, 4:03:53 PM10/31/16

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Did you make sure SPI is enabled?

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Michael Doroshenko

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Oct 31, 2016, 4:04:58 PM10/31/16

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Yes, I enabled it as stated in the instructions.

Mark Setrem

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Oct 31, 2016, 5:33:57 PM10/31/16

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What version of node-red? What version of nodejs? What version of npm?

Which Pi?

Michael Doroshenko

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Nov 1, 2016, 4:21:50 PM11/1/16

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RPi 3

Linux 4.4.23-v7+ arm LE

npm 2.15.9

node v4.6.1

Node-Red v0.15.2

Please advise.

Thanks.

On Mon, Oct 31, 2016, 5:33 PM Mark Setrem <mse...@gmail.com> wrote:

What version of node-red? What version of nodejs? What version of npm?

Which Pi?

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Thanks.

Michael Doroshenko

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Mark Setrem

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Nov 2, 2016, 5:04:11 AM11/2/16

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I just tried installing the node on a new instance of node-red using the same version of nodejs as you

If I install it and have NOT configured SPI to be on I get the same as you, no error messages if I start node-red with the command "node-red -v"

However when I then use "sudo raspi-config" and enable SPI and reboot and the node is then displayed.

One confusing thing is it displays under "Raspberry_Pi" but with the name "A/D Converter" rather than the name "pimcp3008" which the flows.nodered.org page suggests.

Michael Doroshenko

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Nov 2, 2016, 4:15:51 PM11/2/16

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Thank you. I was able to find it under the name "A/D Converter". Not obvious at all...

Now, however, I am facing a different issue: the values I am getting from the 8 channels are constant, even though the board appears to have been wired appropriately (it works fine with a different Python library, which produces non-zero outputs only on adc/0 and adc/1). Specifically, I am alwyas getting these same values from all channels:

02/11/2016, 16:13:41f3b87a22.ccce18function : (warn)adc/0:384

02/11/2016, 16:13:41f3b87a22.ccce18function : (warn)adc/1:400

02/11/2016, 16:13:41f3b87a22.ccce18function : (warn)adc/2:416

02/11/2016, 16:13:41f3b87a22.ccce18function : (warn)adc/3:432

02/11/2016, 16:13:41f3b87a22.ccce18function : (warn)adc/4:448

02/11/2016, 16:13:41f3b87a22.ccce18function : (warn)adc/5:464

02/11/2016, 16:13:41f3b87a22.ccce18function : (warn)adc/6:480

02/11/2016, 16:13:41f3b87a22.ccce18function : (warn)adc/7:496

Is there a problem with this library or am I doing something wrong again?
Thanks!

Michael Doroshenko

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Nov 3, 2016, 9:20:44 PM11/3/16

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This new development is, unfortunately, blocking my project...

I was hoping the node implemented by the Node-RED creator would have a better support.

Please, let me know if you've got any ideas about why I am always getting the same values from the A/D converter node.

Dave C-J

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Nov 4, 2016, 5:06:18 AM11/4/16

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Hi,

sorry for the slow response - but I do have a day job as well, that isn't to do with Node-RED. I'll try to look at it this weekend if I get time.

The node is a simple wrapper around the https://github.com/fivdi/mcp-spi-adc library.

Luckily you are a computer scientist and this is an open source project so you can help debug it. Thanks.

Michael Doroshenko

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Nov 4, 2016, 3:59:17 PM11/4/16

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Hello, Dave!
Thank you for the link. We investigated for a couple of hours, and realized that our MCP3008 was connected to channel CE1, because CE0 was already taken by an RFID reader.
As soon as we reconnected the MCP3008 to channel CE0, your node provided the correct values.

Due to our operational constraints (we cannot modify the hardware setup of the already deployed systems) we would prefer if we could connect your Node-RED MCP3008 node to CE1.
It would be ideal to have this option in GUI, but, if that's not possible, even modifying the node code would be an acceptable acceptable to us.

We tried to reprogram the node

fs.statSync("/dev/spidev0.0"); --> fs.statSync("/dev/spidev0.1");

but it didn't seem to help (although we might have made a mistake somewhere else...)
Is there anything else in the code we would have to modify in order to switch the connection from CE0 to CE1???
Thank you.

Michael Doroshenko

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Nov 4, 2016, 4:20:37 PM11/4/16

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Perhaps, linking all of the A/D converter nodes to a single configuration node where you can specify CE0 or CE1 would be a nice addition for the GUI control.

Mark Setrem

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Nov 4, 2016, 4:51:59 PM11/4/16

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well it is an open source project...

Dave C-J

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Nov 4, 2016, 6:06:50 PM11/4/16

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Hi

try changing line 26

from - mcp3008.push(mcpadc.openMcp3008(i, function (err) {

to - mcp3008.push(mcpadc.openMcp3008(i, {deviceNumber:1}, function (err) {

and report back.. If it works I'll have a look at adding to the UI.

Dave C-J

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Nov 5, 2016, 9:04:30 AM11/5/16

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Hi

took a punt - and published it anyway - now version 0.0.6 on npm.

Michael Doroshenko

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Nov 5, 2016, 6:43:15 PM11/5/16

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Thank you, Dave, and sorry for the delay.
Fantastic work! I seem to be getting the correct values from CE1 now.
Hopefully, this will be helpful to the community as well!

On Sat, Nov 5, 2016, 9:04 AM Dave C-J <dce...@gmail.com> wrote:

Hi

took a punt - and published it anyway - now version 0.0.6 on npm.

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