Wireless UART for debug purposes

[pozz]

I often have embedded boards with a UART that shows debug logging
messages. Most of the times, only the TX signal is of interest, in a few
cases the debug UART features a full command line console, so both TX
and RX lines are of interest.

I have many UART/USB adapters and they work well when I have a desktop
or mobile PC, running putty or Realterm or a similar software, near the
device.

However, in some cases, the device is installed far from a PC and it's
difficult to have USB wired cable connection. So I'm wondering if
there's an off-the-shelf UART/wireless adapter that could help in these
cases. Bluetooth? WiFi? Proprietary wireless protocol (with a
priorietary dongle USB receiver)?

Do you have the same problem as me? How did you solve?

[David Brown]

There are plenty of Bluetooth modules with UART connections, but of
course you need something at the other end. A couple of Silicon Labs
evaluation boards can be configured as linked to each other - then they
can act mostly like a UART cable with a wireless cable, with very little
effort.

If you need to have the Bluetooth module inside the device, and have one
master PC talking to lots of devices, then you'll need to do a bit more
work. And if it is always installed, then suddenly your device is
classified as a radio communications device, with all the standards,
certifications, EMC rules, and testing that goes along with that.

If it is okay to plug something temporarily into the board that needs
debugged, you could set up a Rasberry Pi with a USB battery pack, and
plug that into your TTL-level UART debug signals on the board. Then you
can have Wifi configured in any way you like. A tty to tcp/ip port
converter for remote access should not be difficult to make - with
Python Twisted, it's probably no more than a couple of dozen lines.

[pozz]

I know I can design my own solution, maybe using some evaluation boards.

However I was asking about something ready to use. Plug the wireless
adapter on the debug UART of the device and open putty on the remote PC
(here remote means reachable by the RF signal, whatever it is).

[David Brown]

As I say, look at Silicon Labs Bluetooth modules. There's no point in
me trying to give the details of the devices I used, since that was
three or four years ago, but those were close to out-of-the-box - just
configuration and setup, using the Silicon Labs mobile app. (I was
communicating between two other cards, rather than a PC, but that should
make little difference.) There are no doubt a dozen different vendors
with similar solutions.

You haven't said if you need this for two systems or two thousand
systems, so that's the best answer you can get so far.

[pozz]

I will check.

In the meantime, I found many UART/WiFi adapter based on ESP-01 module.
I think it should be ok.

> You haven't said if you need this for two systems or two thousand
> systems, so that's the best answer you can get so far.

Less than 10 pieces should be ok :-D

[David Brown]

Yes, I would expect it to be easy to get hold of such modules and
ready-made software for the ESP-32 if you prefer Wifi.

>
>> You haven't said if you need this for two systems or two thousand
>> systems, so that's the best answer you can get so far.
>
> Less than 10 pieces should be ok :-D
>
>

Just make sure that they are not considered part of the main system that
you make, so that you don't have to test and certify them.

[Theo]

David Brown <david...@hesbynett.no> wrote:
> As I say, look at Silicon Labs Bluetooth modules. There's no point in
> me trying to give the details of the devices I used, since that was
> three or four years ago, but those were close to out-of-the-box - just
> configuration and setup, using the Silicon Labs mobile app. (I was
> communicating between two other cards, rather than a PC, but that should
> make little difference.) There are no doubt a dozen different vendors
> with similar solutions.

Was it this kind of thing:
https://www.silabs.com/development-tools/wireless/bluetooth/bgm220-explorer-kit?tab=overview

Do you just hook up TX and RX and the default firmware does the rest, or do
you need to program it first?

> You haven't said if you need this for two systems or two thousand
> systems, so that's the best answer you can get so far.

Seems like it's a common thing:
https://www.adafruit.com/product/2479
https://www.waveshare.com/bluetooth-slave-uart-board.htm
https://www.amazon.com/Bluetooth-Converter-Wireless-Transceiver-Communication/dp/B08Z3J9Y8T

and I see there are some Chinese versions for about $2 + shipping:
https://www.aliexpress.com/w/wholesale-bluetooth-uart.html?spm=a2g0o.home.search.0
and for wifi:
https://www.aliexpress.com/w/wholesale-wifi-uart.html?spm=a2g0o.productlist.search.0

It's the kind of thing that's potentially useful to install just in case you
need a recovery console on something like a router, which you can set up
ahead of time so you have access without taking the thing apart when you're
in a jam. Although not entirely happy with the security model of something
broadcasting its pairing ability all the time when not in use.

Theo

[Hans-Bernhard Bröker]

Am 13.11.2023 um 09:10 schrieb pozz:

> However, in some cases, the device is installed far from a PC and it's
> difficult to have USB wired cable connection.

Define "far", and "UART"

If the interface is actual RS232 of modest baudrate, it could be as
simple as: make the RS232 cable long, so the USB doesn't have to be.

[Peter Heitzer]

Or remote control a notebook connected to the devices UART via ssh or
RDP (if you are using Windows).


--
Dipl.-Inform(FH) Peter Heitzer, peter....@rz.uni-regensburg.de

[pozz]

Il 14/11/2023 19:47, Hans-Bernhard Bröker ha scritto:
> Am 13.11.2023 um 09:10 schrieb pozz:
>
>> However, in some cases, the device is installed far from a PC and it's
>> difficult to have USB wired cable connection.
>
> Define "far",

10-15 meters should be ok

> and "UART"

Standard TX and RX asynchronous signals as in RS232 standard, but at
UART low level voltages (3.3V or 5V). Baudrates that I often use are the
standard from 9600bps up to 115.2kbps.

> If the interface is actual RS232 of modest baudrate, it could be as
> simple as: make the RS232 cable long, so the USB doesn't have to be.

The problem with a long cable is often the position of the device that
is uncomfortable to reach. Moreover, if I want to record a long session
log (for one or more days), the long cable isn't an option.

[pozz]

Il 15/11/2023 09:16, Peter Heitzer ha scritto:
> Hans-Bernhard Bröker <HBBr...@gmail.com> wrote:
>> Am 13.11.2023 um 09:10 schrieb pozz:
>
>>> However, in some cases, the device is installed far from a PC and it's
>>> difficult to have USB wired cable connection.
>
>> Define "far", and "UART"
>
>> If the interface is actual RS232 of modest baudrate, it could be as
>> simple as: make the RS232 cable long, so the USB doesn't have to be.
> Or remote control a notebook connected to the devices UART via ssh or
> RDP (if you are using Windows).

As I said, the device is difficult to physically reach and it is often
impossible to install a notebook near it.

[Hans-Bernhard Bröker]

Am 20.11.2023 um 08:29 schrieb pozz:
> Il 14/11/2023 19:47, Hans-Bernhard Bröker ha scritto:
>> Am 13.11.2023 um 09:10 schrieb pozz:
>>
>>> However, in some cases, the device is installed far from a PC and
>>> it's difficult to have USB wired cable connection.
>>
>> Define "far",
>
> 10-15 meters should be ok
>
>> and "UART"
>
> Standard TX and RX asynchronous signals as in RS232 standard, but at
> UART low level voltages (3.3V or 5V). Baudrates that I often use are the
> standard from 9600bps up to 115.2kbps.

Then you need an active device that shifts and boosts signal levels, a
good deal closer to the machine in question. A MAX232 equivalent in a
box small enough to count as a plug casing would probably do it.

> The problem with a long cable is often the position of the device that
> is uncomfortable to reach.

"Uncomfortable" should only rule out doing that for use cases at or
below the urgency of "nice-to-have."

Or, to put it differently: if you can't even get there with a suitable
plug attached to some thin-ish cable, that puts the situation beyond
"uncomfortable," into the realm of "practically impossible to use."