Error writing to 28x2 (AXE401) - SOLVED

vu3hpf

New Member
Hello All,

Hope one of you could help, I have been trying to get my PICAXE-28X2 Shield (AXE401) to work again, Been using this for few years now to prototype projects.

Last I used this board was back in Jan 2020 but it fails now to program. I get the "Hardware not found on COM8!" error.

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Whats confusing is, the same setup (ie Same PC, Editor, COM port, programming cable etc) works fine with a 8M device. I can program it successfully (and not a 28x2 device). I am using Windows 10 and PE6.

I have already tried few new 28x2 devices, tried the "hard reset" options both using power-up during programming and using reset pin on 28x2 but nothing worked so far.

Also noticed that, when I connect the AXE401 shield to a COM terminal, I get the following message. Which shows the 28x2 is able to send messaged back to PC.

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Any help to resolve this issue is appreciated.

PS: I can see similar issue is being discussed here but its still open.

Thanks,
Gopan.
 

Technoman

Senior Member
Hi,

I would first check the position of the jumper links, then use a scope connected to Serial in (pin 6).
 

AllyCat

Senior Member
Hi,

If you're receiving the PICaxe "Welcome" message, then that implies that the TXD path is working properly and the fault must be in the RXD path. Also, if the programming cable is working with another board then that should be OK (otherwise do a "loopback" test on the 3.5 mm plug).

Therefore you should only need to check the RXD path on the AXE401 / shield. The obvious place to start is that "H2" is present and correctly positioned. Do you have a multimeter (or a 'scope) ? If so, check that the RXD path is normally low, but rises to about 5 volts for a short time when you attempt a program download (or Option > "Check Firmware Version", etc.).

Cheers, Alan.
 

vu3hpf

New Member
Thanks Technoman & AllyCat for your responses.

Did a full trace on the AXE401 board and found that the GND pin of the 3.5mm programming socket has no route to board's ground. There was a break in the track (not sure how but it looked like burned out).

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Reconnected the pad and everything is back to normal working.

Thanks,
Gopan
 

inglewoodpete

Senior Member
Did a full trace on the AXE401 board and found that the GND pin of the 3.5mm programming socket has no route to board's ground. There was a break in the track (not sure how but it looked like burned out).
A few years ago I had that same 0v track burn out in similar fashion. I can't remember the exact circumstances but it occurred when I connected something to the I/O pins of the board. Fortunately, I heard the 'crack' as the trace vaporised and I was able to diagnose and repair the board quite quickly.
 
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