Have I broken it?

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vk3jme

New Member
Hello all,

This is my first post, and I'm not sure if it is a good one.

Let me introduce myself.
I'm an IT / Lab tech at my local school.
During my spare time, I enjoy amateur radio.
My bother in law introduced me to PICAXE a few years ago, I have just been waiting for a project to use it on.
I learnt to program z80's about 12 years ago and x86 in assembler about 10 years ago, (too long ago to remember much)

I have a project in the wind of building a APRS radio / GPS controller.
There is a similar device already available, but I want to make a better one!

OK back to my issue with a PICAXE.
I purchased an 18X.
Last night I excitedly interfaced it to my PC and attempted to program it.
I made the programming interface correctly as described, except for instead of a 22K resistor on the Serial input, I used 2x10K resistors in series as I didn't have a 22K.

I was able to talk to PICAXE fine!
I threw together a flow chart, without really reading the instructions.

It was basically:

start:
high 0
wait 1000
low 0
goto start

I can't remember if it was wait 1000 or pause 1000 I used.

I left the high and low commmands as 0, as I thought that high/low 0 used the out port 0.

Now I can't communicate with the picaxe.
My circuit is on a bread board, and I have checked it over and rebuilt it about 10 times now. Everything is fine.
If I apply power to the circuit, I serial out (pin 2) is 0.
If I hold the reset line low and power it on then release the reset line, Serial out goes high. After about 15 minutes, it flashes low for a second or two then returns high.

Have I screwed my picaxe, or is there a way to return it back to factory defaults?

Any help welcome!

Thanks,

Jamie
 
A

alpacaman

Member
I'm fairly new to Picaxe as well. Here is what I found. My circuit/program doesn't appear to work until I unplug the programming cable. I haven't found any documentation on this and I've seen other posts that say their program works when the cable is plugged in. That's just the way it works for me - might be worth a try.
I don't know what you have on your output but it may appear to not work when it is working as programmed. After you set the pin low you're going back to the start of your loop which immediately sets the pin high again.

 
 
B

BeanieBots

Moderator
Hi Jamie and welcome.
Hopefully you used "pause" and not "wait".
Wait is in seconds and has a maximum value of 65.
Pause is in milliseconds, so pause 1000 will give a 1 second delay.

It may be that the PICAXE is 'busy' doing the delay and not responding to a download.
Switch off power, allow any decoupling caps etc to fully discharge. Start the download. As soon as the progress bar pop-up appears, power up the board. This gaurantees the PICAXE is in a reset state emediately the download ties to start.

Also, double check your circuit. Make sure reset is pulled high. The download circuit is NOT a potential divider. The 10k must be on the PC side of the connection not the PICAXE side.

PICs are very tough. I doubt you've killed it without having seen or heard something dramatic or kowingly powered it with 12v.

Good point made by alpacaman. Put another pause after low or you won't ever see the output change.

Edited by - beaniebots on 23/07/2007 14:32:04
 
M

Michael 2727

Senior Member
Picaxes are fairly hardy little beasts, hell they were designed for School Kids.

If you D/L circuit is correct try a Hard Reset, e.g. have the picaxe turned OFF, hit the program button, then before it times out apply power to the Picaxe.
Hitting the Firmware Button will also initiate communication and should return the firmware version of you particular chip.

Good luck and welcome to the forum.
 
hippy

hippy

Ex-Staff (retired)
I agree, a hard reset is the best thing to try; power off then turn on when the pop-up says "Connecting to hardware..." in its title bar.

The 2x10K should be okay for replacing the 22K. The code should also not have damaged anything.

I cannot explain the Serial Out line behaviour; get download working again and then come back to that.
 
M

manuka

Senior Member
Agreed-the problem is no doubt easily fixed (by techniques mentioned above) if freeze ups occur.

Picaxes are almost impossible to destroy! In the 5 years since I stumbled upon & began/using/promoting them,I've not experienced a single loss. In that time hundreds (if not thousands?) of the darlings have been tortured accidentally,but even reversed supply leads & "YOW- TOO HOT TO TOUCH" scenarios have left them unharmed. Stan

Edited by - manuka on 23/07/2007 20:53:29
 
V

vk3jme

New Member
Thanks all for your quick response.
Well after triple checking my circuit and attempting to connect to it using the above methods, I believe I have killed it.

I even changed found another couple of resistors and brought the Serial in line up to 22k Ohm,(now 32K WRTG).
I installed the software on my notebook and still I can't connect to it.

I'm using the 5v line from my PC to power it, so I have a nice 5.11V VCC.
Reset line is held up and at pin 4 it measures 5.1v WRTG.
I installed two LEDs for diagnostics on the TX and RX pins (with resistors).
I can see Pin3 (serial in) on but dim, ( I assume that it is pulsing with data), during the PC trying to talk to it.
But Pin 2 (serial out) does not show any activity.
But if I unplug the PC from the chip and power on the circuit, Pin 2 turns on almost instantly!
By memory the firmware used to report v8.6 FYI.

I'm a bit disappointed, I've sort of been waiting to play with PICAXE for a while now.
I hope that the two 08M's I ordered should arrive tomorrow.
If they work, I will know if my 18X is pooped!
Oh well I've blown $15 before with less fun in less time! :)

Thanks,

Jamie
 
hippy

hippy

Ex-Staff (retired)
<i>I now certain, I used a WAIT 1000 command. </i>

If you try a Syntax Check with such a command you'll find that it will fail, so it probably was a PAUSE or a shorter WAIT.

<i>I even changed found another couple of resistors and brought the Serial in line up to 22k Ohm,(now 32K WRTG). </i>

I'm not quite sure where you are measuring from, but do check that you do not have the 10K/22K wired as a voltage divider, it isn't.

<i>I'm using the 5v line from my PC to power it </i>

Not necessarily a good idea. The 5V line can deliver many amps and failure can see components evaporate or explode, wires melt, tracks peel off PCB's, your PSU, motherboard, CPU and Hard Disk can be destroyed. You risk losing everything.

It's far better to use a 3x1.5V battery supply or a wall-wart and a 7805 regulated PSU. A lab/bench PSU with current limit is the preferable solution because that can prevent all sorts of damage, including inserting chips the wrong way round, or wiring 08, 08M and 14M's with their power connections reversed.

<i>I believe I have killed it </i>

It is possible, and the behaviour of Leg 2 ( Serial Out is not as expected ). The question is, what killed it, because you don't want to keep killing chips.

I would suggest repeating the hard reset technique using battery power. Make sure you are not turning power on too early in the download process and check that you haven't unplugged any serial lines or selected a different serial port while trying to get it to work.

When testing the 08M's, I'd suggest using the following program -<code><pre><font size=2 face='Courier'> Pause 1000
Do
SerTxd (&quot;It's Alive !&quot;,CR,LF)
Pause 1000
Loop </font></pre></code> Once downloaded, switch to the Programming Editor Terminal (F8), select 4800 baud, and you should see the message printed.
 
V

vk3jme

New Member
Hi everybody,

Well I have tried playing around to get the 18X working again too much, and I have given up.
My bad!
I received my 2 new 08m's last week, and I have finally got around to playing with them.
All is working fine and I am happy.

Thanks for your input on trying to resurrect my Picaxe, but nothing worked. I'm just going to write it off as learning experience!


Jamie
 
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