#serialport — Public Fediverse posts

#linux #usb #serialport #eprom #vintagecomputing

Does anyone put there have a recommendation for a USB->25 pin serial port cable?

Specifically I have a Stag PP39 EPROM burner which works fine with a DOS program and I want to be able to use it with Linux and the only physical port on the Stag is a 25 pin serial port.

TIA.

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Adafruit Trinket M0 Moving COM Ports in Arduino

I’ve been playing around with the Adafruit Trinket M0 board in an effort to a) move over to 32-bit Cortex M processors from 8-bit AVRs; and b) get to know CircuitPython a little more. I know there are more powerful boards, but I liked the small form factor of the Trinket M0 and see it as a good way into some of the other SAMD based boards supported by the Arduino IDE in the future too.

But the thing I want to do right now isn’t supported in CircuitPython, so I’m using the Arduino IDE.

It’s great how the board can support either, and it all started out fine, but somehow I’ve managed to get into the position where the board keeps coming up as two different serial ports under Windows.  It is COM35 when in bootloader mode (when you can see the TRINKETBOOT drive) but once I load in a sketch from the Arduino IDE and it starts running it it switches over to COM36. It was starting to get really irritating, especially when I wanted to use the serial monitor, as I was constantly telling the IDE which port to use!

There does seem to be a fix though.  I don’t know if this is a universal fix and it might cause problems further down the line, but it worked for me for now.  I also don’t know if this is a common thing for SAMD M0 boards – I can imagine it being a common issue for any board that re-uses the USB port as a serial port but under a different environment (like the Trinket does in the two modes).

In Device Manager you should be able to see the Trinket under “Ports” with the two COM port assignments as it changes.

But you can tell Windows what port assignment to use, so to make them the same do the following:

1. Check you see which COM port is in use in bootloader mode and then load a sketch and check the COM port number when running a sketch.  For me these were 35 and 36 respectively, but it will depend what other devices you’ve used (I used a lot of different microcontrollers!)
2. In Device Manager right click on the sketch COM port under “ports” and select Properties.
3. In Properties, if you aren’t already admin on your machine, you need to select “Change Settings” which has the admin icon.
4. Under Port Settings, select Advanced.
5. At the bottom you will see COM Port Number – you can select this and swap it from the sketch COM port to the same as the bootloader COM port.  Windows will show it as “in use” and check that you are sure you know what you are doing. I just pretended I did and hit “ok”.

You must be sure to get the right COM port here, I don’t know what happens if you choose the wrong one!  Presumably you’ll get weird things going on if you ever plug in both devices Windows things are that COM port at the same time.

Assuming you chose wisely, at this point whichever mode the Trinket is in – bootloader or running sketches, it should be recognised by Windows as the same COM port and you no longer need to change anything in the Arduino IDE, although I still have to “double click” reset to enter bootloader mode to upload sketches.  I don’t know if this is typical – I guess so, but I can live with that.

Note that dropping the CircuitPython bootloader back onto the Trinket sets it back to a different COM port again, but that just seems to be what it does… I’ll update this post as I discover more and if I uncover and weird side effects…

Kevin

#adafruit #cortexM0 #samd #serialPort #trinket #uart