# Problems with more than one MCP3008

**URL:** <https://discourse.nodered.org/t/problems-with-more-than-one-mcp3008/48860>\
**Category:** General\
**Created:** [24 July 2021 19:48 UTC](https://discourse.nodered.org/t/problems-with-more-than-one-mcp3008/48860 "2021-07-24T19:48:06Z")\
**Posts on this page:** 14\
**Page:** 1

<div class="post-metadata">

**Author:** ![CD2468](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/cd2468/32/45451_2.png) [@CD2468](https://discourse.nodered.org/u/CD2468)\
**Post date:** [24 July 2021 19:48 UTC](https://discourse.nodered.org/t/problems-with-more-than-one-mcp3008/48860/1 "2021-07-24T19:48:06Z")

</div>

Hey all,

I have some problems with 3 MCP3008 adc's  
Every time I try to address one of the MCPs, only the first one that I createt answers.  
The others display the values from the first one.  
If I only have one node in the flow the correct MCP answers.

I testet the setup with a python script to rule out hardware problems. That works fine.  
I use a raspberry pi 2B,  
[# node-red-node-pi-mcp3008](https://flows.nodered.org/node/node-red-node-pi-mcp3008)

I enabled the SPI interface with "dtoverlay=spi1-3cs"  
spidev1.0 --\>first MCP30008  
spidev1.1 --\>second MCP30008  
spidev1.2 --\>third MCP30008

---

<div class="post-metadata">

**Author:** ![Gunner](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/gunner/32/43582_2.png) [@Gunner](https://discourse.nodered.org/u/Gunner)\
**Post date:** [25 July 2021 06:12 UTC](https://discourse.nodered.org/t/problems-with-more-than-one-mcp3008/48860/2 "2021-07-25T06:12:44Z")

</div>

Hello and welcome to the forum.

Without the same hardware, we wouldn't be able to test what you have... but even with, you would first need to supply the flow you are using so we could confim it is even setup properly.

[3: Format your code/flows when posting](https://nodered.org/about/community/#3-format-your-codeflows-when-posting)

---

<div class="post-metadata">

**Author:** ![dceejay](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/dceejay/32/38_2.png) [@dceejay](https://discourse.nodered.org/u/dceejay)\
**Post date:** [25 July 2021 07:56 UTC](https://discourse.nodered.org/t/problems-with-more-than-one-mcp3008/48860/3 "2021-07-25T07:56:16Z")

</div>

Presumably you have configured each to use the correct bus and device number. Do you try disconnecting the others and trying one at a time ?

---

<div class="post-metadata">

**Author:** ![CD2468](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/cd2468/32/45451_2.png) [@CD2468](https://discourse.nodered.org/u/CD2468)\
**Post date:** [25 July 2021 08:53 UTC](https://discourse.nodered.org/t/problems-with-more-than-one-mcp3008/48860/4 "2021-07-25T08:53:52Z")

</div>

Thank you for ansering.

**Example one:**  
Only one MCP is connectet to CS0  
On the first ADC Node I select CS0, and on the second ADC Node CS1  
Now I get on the first Node the correct reading.  
On the second Node I get a new reading from the MCP.  
If i set all chip select to CS1, I get a "0" value on both ADC Nodes. ( because no second MCP is connected)

**Example two:**  
Only one MCP is connectet to CS1  
I get the same result as bevor but with CS0 and CS1 swapt.

It seams to me that the CS from the first node I createt will be used to select the CS for all other ADC Nodes

Here is my Node Red flow:

```auto
[{"id":"fa657575.0358f","type":"pimcp3008","z":"c5b27365.6557c","name":"","dev":"3008","pin":0,"dnum":"0","bus":"1","x":510,"y":80,"wires":[["357ac5e8.42bd3a"]]},{"id":"e208d23.3a62b3","type":"inject","z":"c5b27365.6557c","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":230,"y":80,"wires":[["fa657575.0358f"]]},{"id":"357ac5e8.42bd3a","type":"debug","z":"c5b27365.6557c","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":760,"y":80,"wires":[]},{"id":"eea3cda2.ccad88","type":"pimcp3008","z":"c5b27365.6557c","name":"","dev":"3008","pin":0,"dnum":"1","bus":"1","x":510,"y":120,"wires":[["df7ba289.d5d95"]]},{"id":"dd7ae34c.e13bb8","type":"inject","z":"c5b27365.6557c","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":230,"y":120,"wires":[["eea3cda2.ccad88"]]},{"id":"df7ba289.d5d95","type":"debug","z":"c5b27365.6557c","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":760,"y":120,"wires":[]}]

```

Node Red version [1.3.4 Maintenance Release]

---

<div class="post-metadata">

**Author:** ![Gunner](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/gunner/32/43582_2.png) [@Gunner](https://discourse.nodered.org/u/Gunner)\
**Post date:** [25 July 2021 09:43 UTC](https://discourse.nodered.org/t/problems-with-more-than-one-mcp3008/48860/5 "2021-07-25T09:43:31Z")

</div>

Your flow indicates only two chips, not three... but each one is on the same SPI Bus (1)

Again, I don't have that chip in my random collection (that I am aware of) so just guessing here 😛 So I will leave this one for the more knowledgeable node maintainer.

---

<div class="post-metadata">

**Author:** ![CD2468](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/cd2468/32/45451_2.png) [@CD2468](https://discourse.nodered.org/u/CD2468)\
**Post date:** [25 July 2021 10:44 UTC](https://discourse.nodered.org/t/problems-with-more-than-one-mcp3008/48860/6 "2021-07-25T10:44:49Z")

</div>

Without the chips it is hard to reproduce 😅

To enable the third chip select in node red yot have to edit the pimcp3008.html file.  
Add the third option on Line 40 so its look like that:

```auto
   <div class="form-row">
        <label for="node-input-dnum"><i class="fa fa-toggle-on"></i> Device ID</label>
        <select type="text" id="node-input-dnum" style="width:150px;">
          <option value=0>CE0</option>
          <option value=1>CE1</option>
          <option value=2>CE2</option>  
        </select>
    </div>

```

restart node red, and now you can select CS3 in the ADW Node.  
I'm wasnt shure if that caused my problem, but it didnt work in the orginal version either.

---

<div class="post-metadata">

**Author:** ![dceejay](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/dceejay/32/38_2.png) [@dceejay](https://discourse.nodered.org/u/dceejay)\
**Post date:** [25 July 2021 17:32 UTC](https://discourse.nodered.org/t/problems-with-more-than-one-mcp3008/48860/7 "2021-07-25T17:32:20Z")

</div>

So does that now work ok ? If we add that extra option ?

---

<div class="post-metadata">

**Author:** ![CD2468](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/cd2468/32/45451_2.png) [@CD2468](https://discourse.nodered.org/u/CD2468)\
**Post date:** [25 July 2021 18:45 UTC](https://discourse.nodered.org/t/problems-with-more-than-one-mcp3008/48860/8 "2021-07-25T18:45:58Z")

</div>

Not really,  
With the extra option I can access the third MCP on CS2. But only if there is only one ADW node in the flow.

My problem starts when I am using 2 or 3 MCPs at the same time.  
Are there any restrictions that only one MCP can be used?

---

<div class="post-metadata">

**Author:** ![dceejay](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/dceejay/32/38_2.png) [@dceejay](https://discourse.nodered.org/u/dceejay)\
**Post date:** [25 July 2021 22:24 UTC](https://discourse.nodered.org/t/problems-with-more-than-one-mcp3008/48860/9 "2021-07-25T22:24:58Z")

</div>

Not that I’m aware of. As long as the CE is unique for each I would think it ought to work.

---

<div class="post-metadata">

**Author:** ![CD2468](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/cd2468/32/45451_2.png) [@CD2468](https://discourse.nodered.org/u/CD2468)\
**Post date:** [26 July 2021 08:20 UTC](https://discourse.nodered.org/t/problems-with-more-than-one-mcp3008/48860/10 "2021-07-26T08:20:23Z")

</div>

I found something interesting:  
@Gunner It is possible to reproduce the bug without the Chips:  
When the flow is running use the bash command:

```auto
 lsof /dev/spidev*

```

This will list all open devices. I expected an spidev1.x for each CS.  
instead i get:

```auto
pi@testberrypi2:~ $ lsof /dev/spidev*
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
node-red 1305 pi 22u CHR 153,2 0t0 387 /dev/spidev1.0
node-red 1305 pi 23u CHR 153,2 0t0 387 /dev/spidev1.0
node-red 1305 pi 24u CHR 153,2 0t0 387 /dev/spidev1.0
node-red 1305 pi 25u CHR 153,2 0t0 387 /dev/spidev1.0
node-red 1305 pi 26u CHR 153,2 0t0 387 /dev/spidev1.0
node-red 1305 pi 27u CHR 153,2 0t0 387 /dev/spidev1.0
node-red 1305 pi 29u CHR 153,2 0t0 387 /dev/spidev1.0
node-red 1305 pi 30u CHR 153,2 0t0 387 /dev/spidev1.0
pi@testberrypi2:~ $

```

I assume that every entry stands for an ADC input.  
But then there should also appear lines like:

```auto
node-red 1305 pi 30u CHR 153,1 0t0 386 /dev/spidev1.1

```

So the ohter SPI devices where never open to the MCPs.

---

<div class="post-metadata">

**Author:** ![CD2468](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/cd2468/32/45451_2.png) [@CD2468](https://discourse.nodered.org/u/CD2468)\
**Post date:** [26 July 2021 09:36 UTC](https://discourse.nodered.org/t/problems-with-more-than-one-mcp3008/48860/11 "2021-07-26T09:36:41Z")

</div>

Hello together,  
I got the Problem fixed.

Here are the modified code:

pimcp3008.html

```auto
<!DOCTYPE html>
<script type="text/x-red" data-template-name="pimcp3008">
    <div class="form-row">
        <label for="node-input-dev"><i class="fa fa-server"></i> Device</label>
        <select type="text" id="node-input-dev" style="width:150px;">
            <option value="3008">mcp3008</option>
            <option value="3002">mcp3002</option>
            <option value="3004">mcp3004</option>
            <option value="3202">mcp3202</option>
            <option value="3204">mcp3204</option>
            <option value="3208">mcp3208</option>
            <option value="3304">mcp3304</option>
        </select>
    </div>
    <div class="form-row">
        <label for="node-input-pin"><i class="fa fa-map-pin"></i> Input pin</label>
        <select type="text" id="node-input-pin" style="width:150px;">
          <option value=0>A0</option>
          <option value=1>A1</option>
          <option value=2>A2</option>
          <option value=3>A3</option>
          <option value=4>A4</option>
          <option value=5>A5</option>
          <option value=6>A6</option>
          <option value=7>A7</option>
          <option value="M">set by msg.payload</option>
        </select>
    </div>
    <div class="form-row">
        <label for="node-input-dnum"><i class="fa fa-toggle-on"></i> Device ID</label>
        <select type="text" id="node-input-dnum" style="width:150px;">
          <option value=0>CE0</option>
          <option value=1>CE1</option>
	  <option value=2>CE2</option>	
        </select>
    </div>
    <div class="form-row">
        <label for="node-input-bus"><i class="fa fa-toggle-on"></i> SPI bus</label>
        <select type="text" id="node-input-bus" style="width:150px;">
          <option value=0>0</option>
          <option value=1>1</option>
        </select>
    </div>
    <div class="form-row">
        <label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
        <input type="text" id="node-input-name" placeholder="Name"/>
    </div>
</script>

<script type="text/x-red" data-help-name="pimcp3008">
   <p>Reads from an MCP3xxx Series Analogue to Digital Converter (ADC) chip on the Pi SPI CE0 or CE1 connection,
   such as the rasp.io/analogzero.</p>
   <p>You can either set a channel in the edit dialogue, or you can set the <code>msg.payload</code>
   to select the channel dynamically. If so then the expected payload must be a value from 0 to 7.</p>
   <p>Outputs a numeric <code>msg.payload</code> with a range of 0 to 1023, representing 0V to 3.3V.</p>
   <p><i>Hint</i>: use a <code>range</code> node to re-scale the values to ones you want.</p>
   <p>Also sets <code>msg.topic</code> to <i>adc/{the pin number}</i></p>
   <p><b>Warning</b>: Input voltages must not exceed 3.3V</p>
   <p>The SPI bus must be enabled for this node to work. This can be achieved by using the
   advanced menu (option 9 A5) of the <b>raspi-config</b> utility.</p>
</script>

<script type="text/javascript">
    RED.nodes.registerType('pimcp3008',{
        category: 'Raspberry Pi',
        paletteLabel: 'A/D converter',
        color: "#c6dbef",
        defaults: {
            name: {value:""},
            dev: {value:"3008"},
            pin: {value:0, required:true},
            dnum: {value:0},
            bus: {value:0}
        },
        inputs: 1,
        outputs: 1,
        icon: "rpi.png",
        label: function() {
            return this.name || "mcp:"+this.dev+" "+" bus:"+this.bus+" CS:"+this.dnum+" pin:"+((this.pin==="M")?"":this.pin);
        },
        labelStyle: function() {
            return this.name?"node_label_italic":"";
        }
    });
</script>

```

pimcp3008.js

```auto

module.exports = function(RED) {
    "use strict";
    var fs2 = require('fs');
    var allOK = false;
    var mcpadc;
    // unlikely if not on a Pi
    try {
        var cpuinfo = fs2.readFileSync("/proc/cpuinfo").toString();
        if (cpuinfo.indexOf(": BCM") === -1) {
            RED.log.warn("Info : mcp3xxx : Not running on a Pi - Ignoring node");
        }
        else {
            mcpadc = require('mcp-spi-adc');
            allOK = true;
        }
    }
    catch(err) {
        RED.log.warn("Info : mcp3xxx : Not running on a Pi - Ignoring node");
    }

    //var mcp3xxx = [];

    function PiMcpNode(n) {
        RED.nodes.createNode(this,n);
        this.pin = n.pin || 0;
        this.interval = n.interval || 1000;
        this.dnum = parseInt(n.dnum || 0);
        this.bus = parseInt(n.bus || 0);
        this.dev = n.dev || "3008";
	this.fs = require('fs');
        this.mcp3xxx = [];
        var node = this;
        this.cb = function (err) { if (err) { node.error("Error: "+err); } };
        this.opt = { speedHz:20000, deviceNumber:node.dnum, busNumber:node.bus };
        var chans = parseInt(this.dev.substr(3));
	var node = this;

        if (allOK === true) {
            try {
                node.fs.statSync("/dev/spidev"+node.bus+"."+node.dnum);
                if (node.mcp3xxx.length === 0) {
                    for (var i=0; i<chans; i++) {
                        if (node.dev === "3002") { node.mcp3xxx.push(mcpadc.openMcp3002(i, node.opt, node.cb)); }
                        if (node.dev === "3004") { node.mcp3xxx.push(mcpadc.openMcp3004(i, node.opt, node.cb)); }
                        if (node.dev === "3008") { node.mcp3xxx.push(mcpadc.openMcp3008(i, node.opt, node.cb)); }
                        if (node.dev === "3202") { node.mcp3xxx.push(mcpadc.openMcp3202(i, node.opt, node.cb)); }
                        if (node.dev === "3204") { node.mcp3xxx.push(mcpadc.openMcp3204(i, node.opt, node.cb)); }
                        if (node.dev === "3208") { node.mcp3xxx.push(mcpadc.openMcp3208(i, node.opt, node.cb)); }
                        if (node.dev === "3304") { node.mcp3xxx.push(mcpadc.openMcp3304(i, node.opt, node.cb)); }
                    }
                }
                node.on("input", function(msg) {
                    var pin = null;
                    if (node.pin === "M") {
                        var pay = parseInt(msg.payload.toString());
                        if ((pay >= 0) && (pay < chans)) { pin = pay; }
                        else { node.warn("Payload needs to select channel 0 to "+(chans-1)); }
                    }
                    else { pin = parseInt(node.pin); }
                    if (pin !== null) {
                        node.mcp3xxx[pin].read(function (err, reading) {
                            if (err) { node.warn("Read error: "+err); }
                            else { node.send({payload:reading.rawValue, topic:"adc/"+pin}); }
                        });
                    }
                });
            }
            catch(err) {
                node.error("Error : Can't find SPI device - is SPI enabled in raspi-config ?"+ err);
            }

            node.on("close", function(done) {
                if (node.mcp3xxx.length !== 0) {
                    var j=0;
                    for (var i=0; i<chans; i++) {
                        node.mcp3xxx[i].close(function() { j += 1; if (j === chans) {done()} });
                    }
                    mcp3xxx = [];
                }
                else { done(); }
            });
        }
        else {
            node.status({text:"node inactive."})
        }
    }

    RED.nodes.registerType("pimcp3008",PiMcpNode);
}

```

Now all devises are showing up:

```auto
pi@testberrypi2:~/.node-red/node_modules/mcp-spi-adc $ lsof /dev/spidev*
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
node-red 1886 pi 20u CHR 153,2 0t0 387 /dev/spidev1.0
node-red 1886 pi 21u CHR 153,2 0t0 387 /dev/spidev1.0
node-red 1886 pi 22u CHR 153,2 0t0 387 /dev/spidev1.0
node-red 1886 pi 23u CHR 153,2 0t0 387 /dev/spidev1.0
node-red 1886 pi 24u CHR 153,2 0t0 387 /dev/spidev1.0
node-red 1886 pi 25u CHR 153,2 0t0 387 /dev/spidev1.0
node-red 1886 pi 28u CHR 153,2 0t0 387 /dev/spidev1.0
node-red 1886 pi 29u CHR 153,2 0t0 387 /dev/spidev1.0
node-red 1886 pi 30u CHR 153,0 0t0 385 /dev/spidev1.2
node-red 1886 pi 31u CHR 153,0 0t0 385 /dev/spidev1.2
node-red 1886 pi 32u CHR 153,0 0t0 385 /dev/spidev1.2
node-red 1886 pi 33u CHR 153,0 0t0 385 /dev/spidev1.2
node-red 1886 pi 34u CHR 153,0 0t0 385 /dev/spidev1.2
node-red 1886 pi 35u CHR 153,0 0t0 385 /dev/spidev1.2
node-red 1886 pi 36u CHR 153,0 0t0 385 /dev/spidev1.2
node-red 1886 pi 37u CHR 153,0 0t0 385 /dev/spidev1.2
node-red 1886 pi 38u CHR 153,1 0t0 386 /dev/spidev1.1
node-red 1886 pi 39u CHR 153,1 0t0 386 /dev/spidev1.1
node-red 1886 pi 40u CHR 153,1 0t0 386 /dev/spidev1.1
node-red 1886 pi 41u CHR 153,1 0t0 386 /dev/spidev1.1
node-red 1886 pi 42u CHR 153,1 0t0 386 /dev/spidev1.1
node-red 1886 pi 43u CHR 153,1 0t0 386 /dev/spidev1.1
node-red 1886 pi 44u CHR 153,1 0t0 386 /dev/spidev1.1
node-red 1886 pi 45u CHR 153,1 0t0 386 /dev/spidev1.1
pi@testberrypi2:~/.node-red/node_modules/mcp-spi-adc $

```

---

<div class="post-metadata">

**Author:** ![dceejay](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/dceejay/32/38_2.png) [@dceejay](https://discourse.nodered.org/u/dceejay)\
**Post date:** [26 July 2021 11:38 UTC](https://discourse.nodered.org/t/problems-with-more-than-one-mcp3008/48860/12 "2021-07-26T11:38:40Z")

</div>

Do you fancy raising a pull request so we can fix the node easily. (Otherwise it’ll have to wait until I’m back from vacation)

---

<div class="post-metadata">

**Author:** ![CD2468](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/cd2468/32/45451_2.png) [@CD2468](https://discourse.nodered.org/u/CD2468)\
**Post date:** [26 July 2021 13:17 UTC](https://discourse.nodered.org/t/problems-with-more-than-one-mcp3008/48860/13 "2021-07-26T13:17:24Z")

</div>

So the pull request is created.

I hope I done it right, this was my first request on github. 😆

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [24 September 2021 13:18 UTC](https://discourse.nodered.org/t/problems-with-more-than-one-mcp3008/48860/14 "2021-09-24T13:18:23Z")

</div>

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