# Node-RED MCU - unhandled exceptions causing endless loop?
**URL:** https://discourse.nodered.org/t/node-red-mcu-unhandled-exceptions-causing-endless-loop/83044
**Category:** General
**Tags:** node-red-mcu
**Created:** [21 November 2023 00:11 UTC](https://discourse.nodered.org/t/node-red-mcu-unhandled-exceptions-causing-endless-loop/83044 "2023-11-21T00:11:33Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@shrickus](https://discourse.nodered.org/u/shrickus)
#### Post date: [21 November 2023 00:11 UTC](https://discourse.nodered.org/t/node-red-mcu-unhandled-exceptions-causing-endless-loop/83044/1 "2023-11-21T00:11:33Z")
Not sure if this is an issue inside `moddable` or `node-red-mcu`, but anytime the generated node-red flows running on my ESP-32 hit an error, the whole unit restarts... and fails again.
In my particular flow, I just added a `node-red-node-serial-in` node, which causes this stack trace in xsbug-log:
```
#xsbug-log connected to "main"
Wi-Fi connected to "S&J-Poolhouse"
IP address 192.168.1.107
# Break: importNow: module "events" not found!
#0: importNow
#1: require /home/srickus/develop/node-red-mcu-plugin/mcu_modules/require/require.js:5
#2: (anonymous-522) /home/srickus/.node-red/node_modules/node-red-node-serialport/25-serial.js:5
#3: forEach
#4: RED.build /home/srickus/develop/node-red-mcu-plugin/node-red-mcu/nodered.js:156
#5: (anonymous-243) /home/srickus/.node-red/mcu-plugin-cache/sqd9j8rnmna/main.js:20
#6: (host)
XS abort: unhandled exception
```
I know the support for the `node-red-node-serial` collection is [still wet behind the ears](https://discourse.nodered.org/t/node-red-mcu-plugin-v1-0-integrating-node-red-mcu-edition-into-the-node-red-editor/72693/201), so I'm not totally surprised it did not work out of the gate. Any idea when we can read/write serial data through the gpio Tx/Rx pins? The bigger question is whether this is the right node to use, I suppose. :\*(
But this topic is more about error handling when something like this goes wrong on the MCU code -- right now my mcu is reconnecting to the wifi network like every 5 seconds! As soon as the connection is established, there is this unhandled expection -- perhaps the generated code should catch all of these and just stop? Or at least impose a logarithmically increasing delay before trying again.
Seems like the closer I get to getting my MCU device deployed, the more obscure the errors -- but this is all very exciting, especially for those of us who only get to write code in the "bits-n-bytes" world, not in the world of "events-n-atoms".
---
### Author:  [@ralphwetzel](https://discourse.nodered.org/u/ralphwetzel)
#### Post date: [21 November 2023 06:46 UTC](https://discourse.nodered.org/t/node-red-mcu-unhandled-exceptions-causing-endless-loop/83044/2 "2023-11-21T06:46:52Z")
> [@shrickus](#):
>
> I know the support for the `node-red-node-serial` collection is [still wet behind the ears](https://discourse.nodered.org/t/node-red-mcu-plugin-v1-0-integrating-node-red-mcu-edition-into-the-node-red-editor/72693/201), so I'm not totally surprised it did not work out of the gate.
Well - it's not _wet behind the ears_, it's just still _work in progress_. 😉 No way the standard node will work out of the box...
> [@shrickus](#):
>
> Any idea when we can read/write serial data through the gpio Tx/Rx pins?
You could make yourself familiar with the `Serial` interface in `Moddable` and use this via a `function` node. Not that elegant - but do-able.
> [@shrickus](#):
>
> As soon as the connection is established, there is this unhandled expection -- perhaps the generated code should catch all of these and just stop?
That's not the nature of MCUs. When they hit a (severe) error, they reset and retry. For development purposes, `xsbug` may support you - as it is supposed to halt the MCU at the exception!
---
### Author:  [@shrickus](https://discourse.nodered.org/u/shrickus)
#### Post date: [21 November 2023 22:16 UTC](https://discourse.nodered.org/t/node-red-mcu-unhandled-exceptions-causing-endless-loop/83044/3 "2023-11-21T22:16:29Z")
> [@ralphwetzel](#):
>
> No way the standard node will work out of the box
Yeah, I saw that @phoddie suggested the `serial in` and `serial out` nodes could be ported to use the moddable Serial library. I could maybe help with that if I knew where/how to even start. If that hill is too steep, I'd be happy to test someone else's commits!
> [@ralphwetzel](#):
>
> the `Serial` interface in `Moddable` and use this via a `function` node
So does this mean that the `function` node code is passed to the mcu as-is? I see in the docs that the `function` node is supported (except for async onStart functions). So do i just need to `npm install` the moddable Serial library, import it into my function, and develop code to read/write the tx/rx pins? I assume I'll need to plug an rs-485 ttl -\> uart board into those mcu pins, to handle the serialization of the data?
> [@ralphwetzel](#):
>
> For development purposes, `xsbug` may support you - as it is supposed to halt the MCU at the exception
Ok, good thing to know... I'm currently using xsbug-log to see the errors on the console. Let me try running the full debugger on my RPi desktop.
---
### Author:  [@ralphwetzel](https://discourse.nodered.org/u/ralphwetzel)
#### Post date: [21 November 2023 22:40 UTC](https://discourse.nodered.org/t/node-red-mcu-unhandled-exceptions-causing-endless-loop/83044/4 "2023-11-21T22:40:28Z")
> [@shrickus](#):
>
> If that hill is too steep, I'd be happy to test someone else's commits!
I'm already down that road! 😉 I've spent the last hour to put together a simple (= non optimized) implementation of a serial node. I'd need another day to find a way to test this a bit.
> [@shrickus](#):
>
> So does this mean that the `function` node code is passed to the mcu as-is?
It is.
> [@shrickus](#):
>
> So do i just need to `npm install` the moddable Serial library, import it into my function, and develop code to read/write the tx/rx pins?
No need to install anything! It's much easier: The host is preconfigured with interface modules for its hardware capabilities ([example](https://github.com/Moddable-OpenSource/moddable/blob/public/build/devices/esp32/targets/m5atom_lite/host/provider.js)), put in a global object called `devices`. You just needed to initialize your port and are ready to go ([example](https://github.com/Moddable-OpenSource/moddable/blob/public/examples/io/serial/echo/main.js)).
---
### Author:  [@ralphwetzel](https://discourse.nodered.org/u/ralphwetzel)
#### Post date: [22 November 2023 16:40 UTC](https://discourse.nodered.org/t/node-red-mcu-unhandled-exceptions-causing-endless-loop/83044/5 "2023-11-22T16:40:55Z")
> [@ralphwetzel](#):
>
> I'd need another day to find a way to test this a bit.
Quick update on that: I've stumbled over an [issue](https://github.com/Moddable-OpenSource/moddable/issues/1226#issuecomment-1823051169) with the `serial` driver in Moddable SDK. We need to investigate what's happening there first, before it can be used for a node.
Sorry for the delay...
---
### Author:  [@ralphwetzel](https://discourse.nodered.org/u/ralphwetzel)
#### Post date: [23 November 2023 15:06 UTC](https://discourse.nodered.org/t/node-red-mcu-unhandled-exceptions-causing-endless-loop/83044/6 "2023-11-23T15:06:35Z")
@shrickus
As advertised, I've created an implementation of `node-red-node-serialport` for `node-red-mcu`.
As it's a shim, it's going to be used as soon as you build a flow with `serial in` or `serial out` node for a MCU.
`Serial request` node is not supported.
For further details, you should refer to the [short documentation](https://github.com/ralphwetzel/node-red-mcu-plugin/tree/main/mcu_modules/node-red-node-serialport).
As this is part of `node-red-mcu-plugin`, you need to install / update this currently from the GitHub repo. After some time for testing (Your feedback is welcome!) I'll create a new release...
---
### Author:  [@shrickus](https://discourse.nodered.org/u/shrickus)
#### Post date: [28 November 2023 14:00 UTC](https://discourse.nodered.org/t/node-red-mcu-unhandled-exceptions-causing-endless-loop/83044/7 "2023-11-28T14:00:08Z")
Hi Ralph,
I finally had some time to update and test the `serial in/out` nodes -- thanks for getting that testable in such short order.
I have not yet been successful reading any data from the TTL to RS-485 module connected to my ESP-32 module, but I suspect it's due to my lack of understanding, or just user error. Plus it is not easy to debug since it is running disconnected from the RPi-4 USB (only connected to MQTT broker via Wifi). Do you have any tricks for remote debugging in this case?
I did want to verify that I'm choosing the right configuration for the `serial in` node... as you suggested in the docs, I created a new `serial-port` node using Port/Rx/Tx values of `/P2/R33/T19`:
It seems the ESP-32 pin numbers don't necessarily match the GPIO numbers -- so which ones should I be using here? And does it matter that the generated "name" of the Serial port
contains the trailing characters `:19200-8N2`?
The code appears to ignore that stuff (and I'm not interested in Transmitting right now). I'm mostly wondering if Rx on pin #33 is referring to GPIO-33 or the pin in slot #33.
---
### Author:  [@ralphwetzel](https://discourse.nodered.org/u/ralphwetzel)
#### Post date: [28 November 2023 19:23 UTC](https://discourse.nodered.org/t/node-red-mcu-unhandled-exceptions-causing-endless-loop/83044/8 "2023-11-28T19:23:10Z")
_Pin_ refers to the GPIO _pin_-number according to the hardware definition of your board.
I've chosen 2 _pins_ that were available on my dev board - completely random. The only criteria: They were accessible easy and sitting next to each other.
When wiring those _pins_, keep in mind, that what the MCU understands as TX is RX for your Serial Port monitor.
Until you've successfully crated a first running flow, I'd try to eliminate any complexity. This is my "development setup": An MCU & a `SH-U07A` TTL to USB adapter (as Serial Port monitor), both plugged into the same laptop.
The laptop runs Node-RED with the `node-red-mcu-plugin` and a serial port terminal application that allows me to monitor the data & loop it back to the MCU. If there's an issue, it has to be within this square feet on my table! 😉 That said, it's not clear for me where you're trying to capture the serial data with your setup. A simple sketch would help me a lot...
Here's an easy flow to test your setup. The only thing you need to change is the pin setup. And no - the trailing characters don't matter.
```auto
[
{
"id": "8c8d2482a20754c2",
"type": "tab",
"label": "Serial Port Test",
"disabled": false,
"info": "",
"env": [],
"_mcu": {
"mcu": true
}
},
{
"id": "a2a935c2741add0a",
"type": "serial in",
"z": "8c8d2482a20754c2",
"name": "",
"serial": "631a61ee97b5a76a",
"_mcu": {
"mcu": true
},
"x": 470,
"y": 240,
"wires": [
[
"e236523df59a71e6"
]
]
},
{
"id": "1f8d02cf73ff87a3",
"type": "serial out",
"z": "8c8d2482a20754c2",
"name": "",
"serial": "631a61ee97b5a76a",
"_mcu": {
"mcu": true
},
"x": 470,
"y": 180,
"wires": []
},
{
"id": "e236523df59a71e6",
"type": "debug",
"z": "8c8d2482a20754c2",
"name": "debug in",
"active": true,
"tosidebar": true,
"console": false,
"tostatus": true,
"complete": "true",
"targetType": "full",
"statusVal": "payload",
"statusType": "msg",
"_mcu": {
"mcu": true
},
"x": 640,
"y": 240,
"wires": []
},
{
"id": "a84f667a636fbc57",
"type": "debug",
"z": "8c8d2482a20754c2",
"name": "debug out",
"active": true,
"tosidebar": true,
"console": false,
"tostatus": true,
"complete": "payload",
"targetType": "msg",
"statusVal": "payload",
"statusType": "auto",
"_mcu": {
"mcu": true
},
"x": 490,
"y": 120,
"wires": []
},
{
"id": "4c39157de56783ee",
"type": "inject",
"z": "8c8d2482a20754c2",
"name": "",
"props": [
{
"p": "payload"
},
{
"p": "topic",
"vt": "str"
}
],
"repeat": "",
"crontab": "",
"once": false,
"onceDelay": 0.1,
"topic": "",
"payload": "",
"payloadType": "date",
"_mcu": {
"mcu": true
},
"x": 260,
"y": 120,
"wires": [
[
"a84f667a636fbc57",
"1f8d02cf73ff87a3"
]
]
},
{
"id": "631a61ee97b5a76a",
"type": "serial-port",
"serialport": "/P2/R33/T19",
"serialbaud": "115200",
"databits": "8",
"parity": "none",
"stopbits": "1",
"waitfor": "",
"dtr": "none",
"rts": "none",
"cts": "none",
"dsr": "none",
"newline": "1000",
"bin": "false",
"out": "interbyte",
"addchar": "",
"responsetimeout": "10000",
"_mcu": {
"mcu": false
}
}
]
```
---
### Author:  [@system](https://discourse.nodered.org/u/system)
#### Post date: [12 December 2023 19:23 UTC](https://discourse.nodered.org/t/node-red-mcu-unhandled-exceptions-causing-endless-loop/83044/9 "2023-12-12T19:23:10Z")
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