# Node-red-contrib-mcp23017chip

**URL:** <https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999>\
**Category:** General\
**Created:** [25 December 2020 08:30 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999 "2020-12-25T08:30:32Z")\
**Posts on this page:** 20\
**Page:** 1

<div class="post-metadata">

**Author:** ![PizzaProgram](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/pizzaprogram/32/19431_2.png) [@PizzaProgram](https://discourse.nodered.org/u/PizzaProgram)\
**Post date:** [25 December 2020 08:30 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/1 "2020-12-25T08:30:33Z")

</div>

Marry Xmas to all 🙂  
I've installed and tried today [this mcp23017chip node](https://flows.nodered.org/node/node-red-contrib-mcp23017chip), but it says:

TypeError: Cannot read property 'setBit' of null

- How can I debug it further, what could be the problem?
- Can I see somewhere the source-code of this node?

My guess is:

- it can only handle the default I2C bus (attached to Raspberry Pi directly) and can not recognise 2th bus (available through an [AtTiny85 USB adapter](https://github.com/harbaum/I2C-Tiny-USB/tree/master/digispark)).

![kép](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/1/3/13a18c0e731bd668ce200b771dfe7d242af24d45.png)

Thanks for all hints!

---

<div class="post-metadata">

**Author:** ![zenofmud](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/zenofmud/32/316_2.png) [@zenofmud](https://discourse.nodered.org/u/zenofmud)\
**Post date:** [25 December 2020 08:38 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/2 "2020-12-25T08:38:47Z")

</div>

> [@PizzaProgram](#):
>
> - Can I see somewhere the source-code of this node?

go to the .node-red folder  
then fo to the node\_modules folder  
in there you should see a folder for the node and its's code.

---

<div class="post-metadata">

**Author:** ![PizzaProgram](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/pizzaprogram/32/19431_2.png) [@PizzaProgram](https://discourse.nodered.org/u/PizzaProgram)\
**Post date:** [25 December 2020 09:16 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/3 "2020-12-25T09:16:56Z")

</div>

@zenofmud  
Thanks 🙂 found it here:  
`/home/openhabian/.node-red/node_modules/node-red-contrib-mcp23017chip`

* * *

Also found [this...](https://discourse.nodered.org/t/after-upgrade-failed-to-install-node-red-contrib-mcp23017chip/35492/6) :

> changing `"i2c-bus": "~1.2.2"` to `"i2c-bus": "~5.2.1"` and installing it locally via `npm i /path/to/mcp23017chip` did the thing. All is working good now

It's at the `package.json` file 31. line.

* * *

Although I'm not sure if this part is a must?  
... in the `.../.node-red/setting.js` file add the line as follows:

```auto
functionGlobalContext: {
i2c:require('i2c-bus')
// os:require('os'),
// jfive:require("johnny-five"),
// j5board:require("johnny-five").Board({repl:false})
},

```

# How do I apply changes?

- enough to restart NR?

---

<div class="post-metadata">

**Author:** ![zenofmud](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/zenofmud/32/316_2.png) [@zenofmud](https://discourse.nodered.org/u/zenofmud)\
**Post date:** [25 December 2020 09:49 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/4 "2020-12-25T09:49:56Z")

</div>

> [@PizzaProgram](#):
>
> # How do I apply changes?
> 
> - enough to restart NR?

edit the file,  
apply the change,  
save the file,  
stop NR,  
start NR  
test

---

<div class="post-metadata">

**Author:** ![PizzaProgram](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/pizzaprogram/32/19431_2.png) [@PizzaProgram](https://discourse.nodered.org/u/PizzaProgram)\
**Post date:** [25 December 2020 13:50 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/5 "2020-12-25T13:50:25Z")

</div>

Thanks 🙂

I've hoped it will be so easy.  
But now I have no idea, how to find out, what is the "right bus number"?  
`i2c-11` is not similar to : `"~5.2.1"`

```auto
:~$ sudo i2cdetect -l
i2c-11 i2c i2c-tiny-usb at bus 001 device 013 I2C adapter

:~$ sudo i2cdetect -y 11
     0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- 27 -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- 51 -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

```

---

<div class="post-metadata">

**Author:** ![PizzaProgram](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/pizzaprogram/32/19431_2.png) [@PizzaProgram](https://discourse.nodered.org/u/PizzaProgram)\
**Post date:** [25 December 2020 14:00 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/6 "2020-12-25T14:00:08Z")

</div>

```auto
  "dependencies": {
    "i2c-bus": "~5.2.1"
  },

```

Hmmm... that number seems to be rather the current "NPM i2c-bus modul" 's version number:

> **[i2c-bus](https://www.npmjs.com/package/i2c-bus?activeTab=versions)**
>
> I2C serial bus access with Node.js

---

<div class="post-metadata">

**Author:** ![zenofmud](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/zenofmud/32/316_2.png) [@zenofmud](https://discourse.nodered.org/u/zenofmud)\
**Post date:** [25 December 2020 15:07 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/7 "2020-12-25T15:07:10Z")

</div>

Try `sudo i2cdetect -y 1`

If you look at what you posted

> :~$ sudo i2cdetect -l  
> i2c-11 i2c i2c-tiny-usb at bus 001 device 013 I2C adapter

it shows the bus is 001.

As for `"i2c-bus": "~5.2.1"`

> - `~version` **“Approximately equivalent to version”** , will update you to all future patch versions, without incrementing the minor version. `~1.2.3` will use releases from 1.2.3 to \<1.3.0.

---

<div class="post-metadata">

**Author:** ![PizzaProgram](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/pizzaprogram/32/19431_2.png) [@PizzaProgram](https://discourse.nodered.org/u/PizzaProgram)\
**Post date:** [25 December 2020 15:23 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/8 "2020-12-25T15:23:15Z")

</div>

> [@zenofmud](#):
>
> it shows the bus is 001.

No. You mix USB bus with I2C bus.  
For proof, look at 1 line under it:  
`:~$ sudo i2cdetect -y 11`  
11 is the bus number of that command.  
It is successfully listing both devices under 0x27 and 0x51.

# I've already found the problem:

At `mcp23017chip.js` source file, Line 15:  
` this.i2c1 = i2cBus.openSync(1); `

Currently I'm trying to enhance the component with +1 variable:  
` this.i2c1 = i2cBus.openSync(this.busNum);`

(But it's not saving ☹ )

 ![kép](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/b/6/b650bfe8744273aec0012fff0c35a1f8072a5cc0.png)

---

<div class="post-metadata">

**Author:** ![zenofmud](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/zenofmud/32/316_2.png) [@zenofmud](https://discourse.nodered.org/u/zenofmud)\
**Post date:** [25 December 2020 18:27 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/9 "2020-12-25T18:27:48Z")

</div>

> [@PizzaProgram](#):
>
> I've already found the problem

I suggest you try to contact the author of the node or possibly try one of the other i2c nodes.

---

<div class="post-metadata">

**Author:** ![PizzaProgram](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/pizzaprogram/32/19431_2.png) [@PizzaProgram](https://discourse.nodered.org/u/PizzaProgram)\
**Post date:** [25 December 2020 19:16 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/10 "2020-12-25T19:16:14Z")

</div>

@willhey  
I've successfully enhanced the component to accept Bus number for each chip.  
 ![kép](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/8/4/8452e9fdf1853958c8622914f0a61d5eee068f85.png)

# It can be downloaded [from here...](https://pcpincer.hu/downloads/NodeRed/node-red-contrib-mcp23017chip.zip)

* * *

I can see the device on Bus 11, but the node reports back:  
`Error: Invalid I2C bus number 11`

 ![kép](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/f/3/f35c9eb01fe7a59f13312b8bebd2b666abe15ef8.png)

I have now idea what could be wrong. It should work.  
Somebody have a look at the code please! 🥺

---

<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 December 2020 22:02 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/11 "2020-12-25T22:02:09Z")

</div>

Are you running as root ? You run i2cdetect as root so I suspect you may need this to match

---

<div class="post-metadata">

**Author:** ![PizzaProgram](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/pizzaprogram/32/19431_2.png) [@PizzaProgram](https://discourse.nodered.org/u/PizzaProgram)\
**Post date:** [26 December 2020 03:13 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/12 "2020-12-26T03:13:29Z")

</div>

Good idea to compare, so I've just checked:

```auto
[04:09:56] openhabian@OH:~$ i2cdetect -l
i2c-1 i2c bcm2835 (i2c@7e804000) I2C adapter
i2c-11 i2c i2c-tiny-usb at bus 001 device 008 I2C adapter
[04:10:01] openhabian@OH:~$ i2cdetect -y 11
     0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- 27 -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- 51 -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

```

Node-RED is running from my: `/home/openhabian/.node-red/` directory, so my guess is, it isn't running as root.

---

<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 December 2020 10:46 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/13 "2020-12-26T10:46:46Z")

</div>

What does `ls -l /dev/i2c*` report ? and also `groups` when run as your normal user (it should have i2c as one of the groups it is in).  
You said you have fixed the node to accept the bus number (good) - but have you checked exactly what it is set to just before it attempts to open the port ? Is in a number etc ?

---

<div class="post-metadata">

**Author:** ![PizzaProgram](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/pizzaprogram/32/19431_2.png) [@PizzaProgram](https://discourse.nodered.org/u/PizzaProgram)\
**Post date:** [26 December 2020 11:02 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/14 "2020-12-26T11:02:03Z")

</div>

I've found the problem. (It has nothing to do with user/group/privileges.)

The programmer who wrote the node originally, declared a variable of an 'i2c-bus' instead of 'i2c'.  
A bus can not have a "sub-bus".  
This is the right way to handle it:

```auto
const i2c = global.get('i2c');
const aBus = i2c.open(11, err => {
  if (err) {
    throw err;
  }
...

```

Here is an example to list the possible/supported functions of an I2C bus:

```auto
[{"id":"1d042afc.dc4755","type":"function","z":"34aad6f7.b85c6a","name":"I2C Functionalities scan","func":"'use strict';\n\n// When run, this program will output the same information as the\n// command 'i2cdetect -F 1'\n//const i2c = global.require('i2c');\nconst i2c = global.get('i2c');\nconst BusNumber = 1;\nconst aBus = i2c.open(BusNumber, err => {\n if (err) {\n throw err;\n }\n\n node.debug('i2c Bus opened successful.');\n \n aBus.i2cFuncs((err, i2cFuncs) => {\n const boolToYesNo = bool => bool ? 'yes' : 'no';\n\n if (err) {\n throw err;\n }\n\n console.log('Functionalities implemented by /dev/i2c-11:');\n console.log('I2C ' + boolToYesNo(i2cFuncs.i2c));\n console.log('SMBus Quick Command ' + boolToYesNo(i2cFuncs.smbusQuick));\n console.log('SMBus Send Byte ' + boolToYesNo(i2cFuncs.smbusSendByte));\n console.log('SMBus Receive Byte ' + boolToYesNo(i2cFuncs.smbusReceiveByte));\n console.log('SMBus Write Byte ' + boolToYesNo(i2cFuncs.smbusWriteByte));\n console.log('SMBus Read Byte ' + boolToYesNo(i2cFuncs.smbusReadByte));\n console.log('SMBus Write Word ' + boolToYesNo(i2cFuncs.smbusWriteWord));\n console.log('SMBus Read Word ' + boolToYesNo(i2cFuncs.smbusReadWord));\n console.log('SMBus Process Call ' + boolToYesNo(i2cFuncs.smbusProcCall));\n console.log('SMBus Block Write ' + boolToYesNo(i2cFuncs.smbusWriteBlock));\n console.log('SMBus Block Read ' + boolToYesNo(i2cFuncs.smbusReadBlock));\n console.log('SMBus Block Process Call ' + boolToYesNo(i2cFuncs.smbusBlockProcCall));\n console.log('SMBus PEC ' + boolToYesNo(i2cFuncs.smbusPec));\n console.log('I2C Block Write ' + boolToYesNo(i2cFuncs.smbusWriteI2cBlock));\n console.log('I2C Block Read ' + boolToYesNo(i2cFuncs.smbusReadI2cBlock));\n });\n});\n\nreturn aBus;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":370,"y":600,"wires":[["6300686f.7c8ca"]]},{"id":"6300686f.7c8ca","type":"debug","z":"34aad6f7.b85c6a","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","statusVal":"","statusType":"auto","x":550,"y":600,"wires":[]},{"id":"351e5767.889d5","type":"inject","z":"34aad6f7.b85c6a","name":"","props":[{"p":"payload"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"true","payloadType":"bool","x":180,"y":600,"wires":[["1d042afc.dc4755"]]}]

```

---

<div class="post-metadata">

**Author:** ![PizzaProgram](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/pizzaprogram/32/19431_2.png) [@PizzaProgram](https://discourse.nodered.org/u/PizzaProgram)\
**Post date:** [26 December 2020 11:15 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/15 "2020-12-26T11:15:35Z")

</div>

I've already modified the component, but can not test it yet, because I've changed some version numbers at the package.json file, and since then none of the flows can start.  
[package.json](https://discourse.nodered.org/uploads/short-url/arBd7rVIf8A7y4OovAhRHhHYbEJ.json) (1,5 kB)

First I have to learn more about how to configure that file properly to keep backward compatibility (for auto-update?) but show improvements _(with version number and description + later maybe I'd also like to add some help-examples)_.

---

<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 December 2020 11:42 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/16 "2020-12-26T11:42:13Z")

</div>

Well it depends what you intend to do with it... - Ideally contact the original author and ask if he is interested in a pull request - you can find the owner from `npm owner ls node-red-contrib-mcp23017chip` - as I can't see he has published the source on github directly. If he is interested (as the last update was only a couple of months ago he may well be) - then hopefully he will make the source public and you can create pull request directly on it. You shouldn't need to change the package.json as he should do that as part of releasing the package - but if you did then you would only need to bump the minor version number - eg from 0.1.0 to 0.2.0.

(but it is Xmas so don't expect instant replies etc)

---

<div class="post-metadata">

**Author:** ![PizzaProgram](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/pizzaprogram/32/19431_2.png) [@PizzaProgram](https://discourse.nodered.org/u/PizzaProgram)\
**Post date:** [26 December 2020 12:13 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/17 "2020-12-26T12:13:11Z")

</div>

I've contacted him already yesterday. Linked this topic. No answer yet.

> [@dceejay](#):
>
> (but it is Xmas so don't expect instant replies etc)

Probably because of that. 😃

I've decided to re-distribute the finished node myself again.  
Maybe even renaming it to `node-red-contrib-multi-i2c-mcp23017`  
to show it's intended to use multiple of it, not just 1 and to help search for "i2c" keyword too.

I find `0.x.y` versioning overcomplicated + confusing for beginners. ❌  
Also I hate when developers make groundbreaking, data-destroying changes, but increasing only from `2.5.2` to `2.5.3` _(Like FirebirdSQL developers did once.)_

`"1.2 (2020-12-26)"` is easier to follow, also in the change history. ✅  
_( "1" is major, ".2" is for minor changes. + an ISO formatted date.)_  
`"1.3 (202y-mm-dd)"` \<\< After adding some examples  
`"2.0 (202y-mm-dd)"` \<\< As soon as I add **"auto-bus-search"** function.  
etc...

---

<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 December 2020 12:18 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/18 "2020-12-26T12:18:37Z")

</div>

Please give him a chance to reply first. Having multiple versions of the same node just adds to the confusion. Please don't create yet another node. And if you really have to - then please stick to three level semantic version numbers otherwise things like npm may not cope well and so not detect updates correctly.

---

<div class="post-metadata">

**Author:** ![knolleary](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/knolleary/32/3_2.png) [@knolleary](https://discourse.nodered.org/u/knolleary)\
**Post date:** [26 December 2020 12:41 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/19 "2020-12-26T12:41:23Z")

</div>

> [@PizzaProgram](#):
>
> find `0.x.y` versioning overcomplicated + confusing for beginners. ❌  
> Also I hate when developers make groundbreaking, data-destroying changes, but increasing only from `2.5.2` to `2.5.3` _(Like FirebirdSQL developers did once.)_
> 
> `"1.2 (2020-12-26)"` is easier

If you are publishing to npm then you _must_ use x.y.z pattern for the version string - you have no choice in the matter.

You can add whatever description you want in the readme.

> [@PizzaProgram](#):
>
> Also I hate when developers make groundbreaking, data-destroying changes, but increasing only from `2.5.2` to `2.5.3` _(Like FirebirdSQL developers did once.)_

Absolutely. Version strings should follow semantic versioning rules so the nature of a version change is clear. See [semver.org](http://semver.org) for details. But if course that relies on the developer setting the version to follow the rules and mistakes do sometimes get made.

But it's far better to stick to the very well established norms rather than go your own way.

---

<div class="post-metadata">

**Author:** ![PizzaProgram](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/pizzaprogram/32/19431_2.png) [@PizzaProgram](https://discourse.nodered.org/u/PizzaProgram)\
**Post date:** [26 December 2020 12:56 UTC](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999/20 "2020-12-26T12:56:48Z")

</div>

I've just realized, the problem has nothing to do with the `package.json` file.  
Under the Manage Palette there was a hidden error report:  
 ![kép](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/2/8/28f31b3f22042fb9ce024dafa00c5cdd308f19e4.png)

Strange, because that code works fine within a function.

[Next page](https://discourse.nodered.org/t/node-red-contrib-mcp23017chip/37999.md?page=2)