Cannot program an 18M chip but other devices okay.

[ashleylad]

Dear all,

I have programmed many different types of PICAXE without out a hitch.

Last night I was playing on my breadboard creating some programs. I used a few 08M a 14M and a 20M, all no problems. I then plugged in a new 18M which I got from Rapid several weeks ago and it comes up hardware not connected. It's the first time since I started playing with PICAXE that I have tried an 18M. Been pulling my hair out, and finally given up. Do you think it could just be a duff chip, or have I overlooked something with that device. After messing I tried the 20M in place and that was fine.

I have the latest editor software installed.

Thanks in advance.

cheers

 

[Andrew Cowan]

The 08M, 14M and 20M all have +V, 0V, serial in and serial out at the top.

However, on the 18 series chips, power is in the middle, and serial in and out are on the left - have a look at the pinout.

You'll need to rewire your breadboard to program one.

Andrew

 

[ashleylad]

Hi Andrew thanks for the quick reply. I did not mention I am not a novice in electronics. I have been breadboarding projects for over twenty years. It's the first thing I noticed about the 18 series. It's a shame the power connections are not the same as the others. In my opinion it makes final wiring on a piece of stripboard or pcb easier.

I have wired the connections correctly, and double checked them with my logic probe and a meter, just to make sure.

I also forgot to mention I tried the reset pin with a 4k7 pull up and a momentary switch to ground still nothing, as pointed out on the data sheet.

I have ordered a handful more chips from Rapid and also from Tech Supplies, including the new 18M2 to try.

Hopefully they will be here today and I can prove if the chip is duff or not. Out of all the PICAXE devices and PIC micros and AVRs never had a bad one.

Cheers

Ashley

 

[scoop]

I had something similar to this with an 18X last week. I was programming and re-programming the chip with no problems at all and then all of a sudden I got the hardware not connected message.

The only way I get get it working again was to disconnect power to the picaxe circuit, press program and when the download box came up reconnect the power again.

Hope it helps.

 

[inglewoodpete]

ashley, can you tell us when you are using as a power supply for the 18M. Apart from bad connections, the supply voltage and stability has a bearing on the ease of programming of PICAXEs.

 

[ashleylad]

inglewoodpete - I am using a Farnell LS 30-10 Benchtop Mains PSU set to +5V can current limit is set to 500mA, which I loan from work to do all my hobby circuits, It's a great unit and can supply some hefty current if required. I have Small ceramic and electrolytic deoupling on the breadboard rail and power wire length is kept to a minimum.

Don't want to waste anyones time, but these scenarios really frustrate me, and keep me awake at night! I know it's only a £2 or so device, but I am sure I am not the only one.

scoop - Thanks for the headsup will give that a try.

cheers

Ash

 

[manuka]

Try 3 x AA - I've never had any programming troubles with any PICAXE when AA batteries are used.

 

[Dippy]

Have you got an 18X ?
An 18X should load OK (noting the 'Reset') in same circuit config as your 18M2 and would be a second-opinion test that your circuit is correctly assembled.

Have you got a scope to see if there is activitity at the Serial Out pin when you are trying to programme it?
Does anything happen if you tie pin 4 high with a res?

I'm sure if this was an intrinsic fault then this would have cropped up hundreds of times so far.
It's either your setup or a duff chip.
Unlikely a duff chip - unless it has been poorly handled in between Rev-Ed programmer and your usage.

I genuinely hope it's not a 3xAA versus 5V supply issue...

 

[hippy]

First thing to try is the Hard Reset procedure - Power-off or press the Reset button before initiating download and only power-on or release from Reset when the "Connecting to hardware..." message is shown.

Second, if that does not resolve the issue, is to try a Firmware Check ( View -> Options -> Mode ), then run through the Serial Test ( View -> Options -> Port ) to see what voltages are appearing on the Serial In pin.

 

[ashleylad]

Dippy no I have not got an 18X.

I have access to a scope, but not used it...yet. I have tried tying pin 4 high with a resistor, does not change anything. My new chips have arrived at work just now, so I will try all your sugggestions and report back later tonight. I have got another couple of 18M chips and an 18M2 to try.

Thanks all will be in touch.

Ash

 

[Pauldesign]

Yeah Ashley, that one pain in the... that all newbie picaxers faced and even experience one are still facing. Sometimes picaxe chips are just programming allergic and you may think they're duffed, broken etc but they're still intact.

I have such problems esp with 18 family and i succeeded by varying the supply voltage until i got them to program well at around 2.5 to 3V and has i've doing so for 3 months. After a while i try to program it again to no avail. I allow it to rest for 2 days, then try programming again, first with a basic code, Voila!.

A lot has been covered on this forum with regards to programs downloading issues. Do a forum search and you'll be frightened with issues, possible causes and workarounds methods.

I'm recently having problems downloading codes if IR LED is connected to the Tx download pins but programs well if a normal LED is connected.

I think, i rather post this as a new thread instead of kidnapping yours which is always the case.

Ooops, i guest i just did

 

[hippy]

I'm recently having problems downloading codes if IR LED is connected to the Tx download pins but programs well if a normal LED is connected.

It probably depends on what forward voltage the LED has and what value current limiting resistor is used; the output signal can become clamped too low and the serial is not recognised. High resistances, piezo and digital logic inputs, connected to the pin should not have an adverse effect but other things can, including LCD data or control lines. That's the reason some PICAXE boards have a "program/run" molex selector for the Serial Out line.

If having problems and something is connected to the Serial Out pin it's a good idea to disconnect that to see if it improves things.

Unfortunately there is no universal, "this is what's wrong", answer to download problems, it's a matter of determining what the issue is in the particular case. Most issues are supply related, batteries flat ( can sink too low when running even if a meter shows a reasonable voltage ).

Making the 10K and 22K download resistors a potential divider or using wrong values can have an impact, reducing the Serial In voltage. Lowering the supply voltage relatively speaking is the same as keeping the supply the same but increasing the Serial In voltage. A Serial Test and checking voltages may help there.

For home built circuits and boards, home built and non Rev-Ed cables, the number of potential issues and mistakes which could be made increases dramatically.

I'd recommend having an AXE003 PICAXE-08M Starter Pack, AXE027 / AXE026, AXE001 PICAXE-08 Proto Board and PICAXE-08M, or some other Rev-Ed board to hand then it's a simple matter of comparatively checking, if a particular board doesn't work, against a board that is more likely to work.

 

[inglewoodpete]

inglewoodpete - I am using a Farnell LS 30-10 Benchtop Mains PSU set to +5V can current limit is set to 500mA, which I loan from work to do all my hobby circuits, It's a great unit and can supply some hefty current if required. I have Small ceramic and electrolytic deoupling on the breadboard rail and power wire length is kept to a minimum.

Yep, it can be frustrating when things like this don't work.

Your power supply setup sounds good. Personally, I've never had chip recognition problems that I could hang on a 5v regulated power supply. However, some advocate 3xAA as a test. It is an option you could try - even if just to eliminate it.

I've not tried an 18M or 18M2 but have used an 18X. I have to say the 18X is the fussiest of the PICAXEs that I have tried but only when downloading data (memory verification error). Never a problem with recognising the chip. But I digress.

Two things we have not cleared up:
1. Which programming cable are you using? I have had trouble in the past with an aftermarket USB/Serial conversion cable (Prolific chip) but problems were rare. The AXE027 has proved to be the most reliable.

2. Your hardware setup: you say you're using a breadboard. The wiring of the 22k + 10k resistors is critical: they do NOT form a voltage divider.

 

[ashleylad]

Mmm, interesting about the serial cable. I am using a home wired serial cable with the resistor chain soldered in the d-shell, connected to a usb-serial device I bought of the web. Maybe it is this causing the problem. Only issue I have at home is only got a laptop now and no serial port! I could try a work pc with the REV ED serial cable.

Hopefully will get chance tonight after work to have another play, all being well so I can close this chapter and thread.

Ash

 

[Pauldesign]

Ashley sorry to hijack your post although nevertheless it's still part of possible future issues that might be encountered.

Yeah Hippy, i forgot to say that's how i've been programming all my picaxes used in IR coms, i.e by removing the IR LED before programming but what amazes me is the fact that, IR LED of all the LEDs, needs the smallest Vf to operate which means the other LEDs should be the one to affect programming, since most of the Tx voltage will be drop across them or is it because since IR LED has the lowest Vf and because of their chemical/electrical properties, thus gets turn ON easily and interrupts the TX line.

Ashely, have you done a forum search? You may only use USB to serial drivers provided by Rev Edu websites.

 

[hippy]

I suspect what's happening is something like ...

--------------.
       ___    |_
5V ---|___|---|_|----.----> TX
              |     .|.
              |     |_|
              |     _|_
              |    _\./_
              |     _|_

The LED clamps its anode voltage at Vf so the output voltage is K*(5V-Vf) + Vf, where K is the potential divider effect. So if both R were the same, Vf=1V, you have 4V across the resistors, 2V across each, output would be 3V. The lower the Vf the lower the output voltage.

I think - someone will correct me if I'm way off the mark,

 

[inglewoodpete]

Mmm, interesting about the serial cable. I am using a home wired serial cable with the resistor chain soldered in the d-shell, connected to a usb-serial device I bought of the web. Maybe it is this causing the problem.

Future problems here. When you finally(!) program the PICAXE and unplug the serial cable from your circuit board, the PICAXE will become unstable.

Read Manual 1 on the Minimum Operating Circuit.

 

[Dippy]

Absolutely Pete.

And to Ashley, please ALWAYS tell us right at the start any circuit details ESPECIALLY if you have some non-standard connection.

I KNOW that, in theory, if it works for one then it should for others. Yes, it is usually the case and it may be another issue in this case but it's nice for people to know. Then they can suggest tests.
I realise you've been 'at it' for many years. So have dozens of people here and we still (yes, even Westy) make mistakes

I don't understand Paul's description so not sure if the hippy sketch is representative of what Paul describes.
I'm not sure what that small square thing is to the right of the resistor.
(Can someone buy him Coreldraw for his birthday please )

You should be able to do the maths with a little subsitution.
You know I = (Vin - Vf) / (R1 + R2) -- assuming PICAXE input is inf impedance.
and Voltage at Tx = Vin - (I * R1) wrt ground
Vin = 5volts in hippy's example
Vf = LED forward voltage (sadly this varies with current but let's keep it simple)
R1 = input series res
R2 = LED series res
I hope I haven't typoed.
Substitute and rearrange ...

I'm sure if you used a nice high-brightness LED and a 10K res for R2 you'll be able to see it nicely and the V will be comfortably above the threshold..

 

[ashleylad]

Gents, thanks for taking the time to reply to this thread, and Dippy yes for future posting including all information at the start is paramount especially non standard bits. A slight oversight on my part, thank you.

Hopefully will make some headway. Right back coffee cup is empty back to work.

Thanks again to all,

Ash

 

[Pauldesign]

Bingo! 330R in series with the IR LED did the trick.

Kudos, old men.

 

[ashleylad]

Sorry late getting back. Tested my new delivery 3 x 08M made an led blink. 2 x 14M made an led blink. 2 x 20M made and led blink. 2 x 18M and 1 x 18M2 no hardware found.

Tried suggestion of 3AA power and my own serial cable. Bingo, all the 18 devices connected and I could program them. Tried with the +5V psu, no problems providing the chip had been programmed using the batteries. As they have all been programmed once they all work now.

So now I am happy and I can sleep at night, and I can move forward.

Can't thank you all enough for you help. I will invest in a usb/serial cable and some proper pcbs for each family to do things right.

I am sure this won't be my last post.

Cheers

Ash

 

[Dippy]

So, are you saying that once the 18M had been programmed first at 4.5V (nom VDD) that it happily programmed at 5V afterwards?
But all attempts at programming a virgin 18M2 at 5V VDD failed?

That is odd. Seems totally mental. Could something else be causing this?

Can anyone else verify this or has anyone else noticed this?
This should be double-checked by others.

 

[Pauldesign]

Glad to hear it now works (yours even, was within weeks, mine was within months).

You can see, they weren't duffed or broken as you thought and hey, don't think you're off the hook yet as you'll be having such future issues some of the times but at least you now know what to do.

And please, always search the forum first regarding whatsoever as this is a common nightmare to all new picaxers and a lot and other things have already been covered to an unbearable extend.

 

[hippy]

There hasn't been any widespread reporting that factory fresh 18M2's won't program that I'm aware of and it seems unlikely that it's a case of once programmed at 4V5 they can then be programmed at 5V but not unless progammed at a lower voltage first. Downloading a new program into a PICAXE won't change its electrical characteristics in any way.

The PICAXE-18M2 is pre-programmed with a test program so it can be installed, Programming Editor or AXEpad configured for 18M2 on the correct serial port, then the Terminal opened to see the 18M2 reporting its presence. It may be this which is causing issues with initial program downloads though it should not. A Hard Reset ( power on when "Connecting to hardware..." is shown ) should allow the device to be programmed. Such a Hard Reset may have occured when using batteries but not with the 5V supply.

That doesn't explain the 18M though. We will investigate the issue further.

 

[Pauldesign]

I've had instances where i couldn't program but 18X and 28x2 (which i should have verifiy this with 18M2, had Tech Supplies shipped my x4 18M2 instead of an empty parcel that they sent ) at 5V but program well between 2V and 3V3 only and not even 4V or 3.5V

Tried 5V (battery/PSU sources) again and didn't still work but do between 2 and 3.3V from both EMF sources.

After 3 months, it refuse programming at all. Smack it and keep it to rest for 2 days and try programming again. Voila.

Sometimes (08M), if i modify same source code and program, it program successfully but still retain the previous source code functionality.
Power cycle but still the same.

Download a fresh simple program: e.g

main:
high o
wait 1
low 0
wait 
goto main

Bingo!

Modify the previous long source code again and re-program. Voila.

Hmmmmm

28x1, 40x1 and 20x2 program perfectly and no intermittent whatsoever issues.

 

[hippy]

had Tech Supplies shipped my x4 18M2 instead of an empty parcel that they sent

Please contact our sales staff at Rev-Ed offices with customer and order details and we will investigate what has happened in this case.

On downloading in general, most people don't seem to run into problems ( and thousands of PICAXE have been programmed countless times ), but some do. It's very difficult to say what the problems are in such cases as there are so many factors at play and it's not easy to diagnose remotely. For devices which don't have a Reset pin and have low operating voltage, a lingering power supply voltage can interfere with the power-cycling reset. It may be worth turning power off, leaving a while, shorting +V to 0V to discharge capacitors, then trying download, powering up when "Connecting to hardware..." shown.

Depending on how and what the PICAXE connects to there can also be parasitic powering issues. Download tests with the PICAXE not connected to anything but the minimal download circuit can help to identify those.

While PICAXE are generally robust, even brief shorts of outputs, over-loading of inputs or outputs can have a long term effect on the chip. Most components don't simply fail but it's always a possibility. In the time I've used PICAXE I've had one (18X) totally fail and one (forget) which also needed voltage to be lowered to program, but only sometimes. It was definitely my own mistake in killing the 18X, and I suspect so for the other.

 

[Dippy]

That could be something entirely different Paul. I've seen a number of post (including from old Lags) where different supply voltages affected programming success. Remember, voltage and temperature affect resonators, but I'm not sure if there was a definitive response as workarounds were so easily done.

I'm referring to the reported apparent behaviour of a virgin 18M(2) not happy at 5V and then, after being 'broken in' at 4.5V, magically OK at 5v thereafter.
Electrically this makes no sense.

I was wondering if this had been seen by others or whether it could be something in the rest of the circuit that was contributing.
- remembering that Ashley's download cable was slightly non-standard.

I've never heard of this before, and as it seems impossible I naturally assume that something else is at work... but that it was worth a second look.

 

[Pauldesign]

Please contact our sales staff at Rev-Ed offices with customer and order details and we will investigate what has happened in this case.

Hippy, thanks for the comment and to follow up.

Yes, i did complained and they promised me, they've or will send it through Fedex but how must i believe their promises if maybe something else will happen. (before they didn't follow my instructions in the comment field; one component wasn't packed and they didn't informed me; now a small order with just 4 components weren't packed besides the first missing component). What is next?

What made me so frustrated is the fact that this is the second time in a row (of which in the first delivery, one component was missing and they did apologize and assured me there are measures in place and it will never happen again) and within 2 months in a row it has happen again (and this time just the missing component in the first order was sent and the items for the order #11319 weren't included).

I really need those components for my thesis, which is due in two weeks time and what worries me is that, the previous deliveries took upto 30 days via airmail transportation. I told them i can't afford to waste a year for Tech Supplies recursive mistakes.

It sounds unethical complaining this in the forum and i apologize but i've to do this so that more attention will be paid to, especially when sending intentional parcels and maybe if measures are taken and implemented in the warehouse, future frustrations will be prevented to others.

Well, i'm just hoping this time it's not a totally empty parcel they've or will send and provided they've or will send it via Fedex as promised, otherwise there is no need even bothering sending.

If the main stores can be doing this what about other local outlets.
Anyway, they did compensated me last time by sending an extra component i wish they do the same this time.

 

[ashleylad]

Guys, did not intend to send people off on a tangent, I am just glad they are working. I suspect most likely that the fact I was using an external psu and a combination of a home brew cable this would be the most likely cause. Underload the 3 cells were supplying about 4.20V measured.

I agree it's mental, and electrically it does not seem possible. May be it was something else, although I do not have one of all the PICAXE family, it did seem odd only 18pin devices had issues.

I will order some bits from Tech supplies like the proper usb/serial cable and some of the small 8,14,18,20 pin pcbs and try again with some new chips.

It may be some time as I have loads of bits to use up first.

Thanks to all.

Ash

 

[hippy]

@ Pauldesign : I can only apologise on behalf of Rev-Ed for any failures there may be. I don't know the particulars of these cases but can understand your being aggrieved. All of us recognise reputation is based on performance and ability to deliver and we strive to keep our reputation high in all areas, often going that extra yard where we can.

We are only human though and everyone can sometimes fall short but we aim to put that right as best we can and ensure the issue does not arise again. I know it's little comfort to hear how we aim to have no packing and shipping mistakes when you've been a victim of that so perhaps the best I can say is that we do care when things go wrong no matter where in the business. Staff care about far more than getting stuff out the door, money in and their pay at the end of the day. As much I'd like, we cannot undo what has been, so I can only offer apologies and say we always aim to do better.

 

[ashleylad]

All I can say is I used them for the first time last week. Purchased smt versions of 08M,14M and a new 18M2 chip also. Used paypal, which is very handy to be honest and the goods turned up within a day or two, well packed, good service. I am sure they ship large volumes of orders and human error creeps in from time to time.

Hippy, I usually get devices from Rapid as I end up loading my basket to get free delivery. I noticed they do not sell the new x2 devices or the new 18M, do you know if they may in the future?

Cheers

Ash

 

[hippy]

I believe, from a previous posting by Technical, that Rapid are stocking the 18M2, they have a part number for it, but haven't updated their pages yet. On the X2's I don't know the status of those.

 

[ashleylad]

Thanks Hippy.

What do you know, just had a look. One week after I placed an order with them the M2 is listed, same price as an 18M. A bargain considering the new specs.

Cheers

 

[Pauldesign]

Just received the parcel from FedEx and hopefully it wasn't empty this time and guess what was inside; one extra 18M2 included.

I wish it could be like this all the time so that i can be having free components.

Thanks for the concern Hippy, i knew it was just human errors and i was just getting my frustrations out otherwise Tech Supplies, just like PICAXE chip, is AWESOME.

 

[Technical]

What made me so frustrated is the fact that this is the second time in a row (of which in the first delivery, one component was missing and they did apologize and assured me there are measures in place and it will never happen again) and within 2 months in a row it has happen again (and this time just the missing component in the first order was sent and the items for the order #11319 weren't included).

We have checked this out as it is very unusual set of events.

On your original order the 28 pin SM device was out of stock the day your main order was processed, and so was actually shipped the very next day by non-insured airmail separately. It appears this second package containing just that chip was lost in the post and never got to you. Unfortunately South Africa post does not have a good track record with us on that front....

On the second shipment, as requested, we placed the missing chip from the first order manually in the packing tray with your paperwork, bypassing the normal system. Unfortunately this was then sent out immediately by the warehouse staff without realising it was actually also a new order. This was a genuine human error mistake, actually caused by trying to fix the first missing part issue! When you emailed us the missing parts were then sent immediately by FedEx at our expense.

We do our best, but occasionally we get it wrong and so we genuinely try to fix it. We are pleased to hear the chips have now got to you safely.

 

[courchaa]

18M Programming problem

Dear all,

I have programmed many different types of PICAXE without out a hitch.

Last night I was playing on my breadboard creating some programs. I used a few 08M a 14M and a 20M, all no problems. I then plugged in a new 18M which I got from Rapid several weeks ago and it comes up hardware not connected. It's the first time since I started playing with PICAXE that I have tried an 18M. Been pulling my hair out, and finally given up. Do you think it could just be a duff chip, or have I overlooked something with that device. After messing I tried the 20M in place and that was fine.

I have the latest editor software installed.

Thanks in advance.

cheers

Have not submitted a post before (Hi to all members!) but thought my experience of the last 2 days may be of interest (will try to keep it brief).
Have taught programming with PICs (especially the 18 series) for some years and came to program the 18M last thursday for first time (70 chips bought from Rapid) - I did this with 3 groups of students at different times. The setup is:

prog editor on a network
axe026 serial cable
5V supply from a triple o/p bench supply (Rapid)
circuits on breadboard
custom made interface box containing 2 resitors and 3.5mm stereo jack (circuit taken from picaxe starter book)

First group I had - disaster 2/20 students managed to program the 18M - thought it could be poor circuits so checked these after the lesson (I teach in a college) and most seemed fine.
second lesson - same result as first - 3/19 programmed ok

third lesson, same initial disaster but started investigating in lesson with students help and we managed to program all but 2 circuits - here are some techniques which we tried:

reset serial port and IC type - even though this had been set it worked for 2
powering down and powering up on programming (worked for 2)
using reset on programming (worked for 3)
as soon as 'cannot connect to IC' message is seen, press OK and immediately press F5 (program shortcut) - this one worked for 8 students so could not be a coincidence??
tried programming at 4.5V but no joy

All of these 'solutions' may well be red-herrings but thought may be of interest.

Best wishes

 

[Technical]

custom made interface box containing 2 resistors and 3.5mm stereo jack (circuit taken from picaxe starter book)

This is probably your mistake. The two resistors are part of the minimum operating circuit (see part 1 of the manual) and therefore must be on the student breadboards at all times. They cannot be 'built into' the cable.

Your results show something is not right, with correctly built circuits you should have pretty near 100% download success.

 

[John West]

This is just a reminder to all that the voltages and current sourcing characteristics of various serial port drivers and USB port devices varies and may not be sufficient for all situations.

From years of experience I can tell you that chip manufacturers do not always produce devices that meet the defined standards - while hoping that the manufacturers of the devices they are communicating with do. Question the source of the programming signal - even if it works properly with some other PICAXE versions it may well be borderline in its operation with others.

There have been many other threads on this topic but here's another list of possibly helpful hints for programming problems:

Follow the Rev. Ed. instructions to the letter (don't make any assumptions about the functionality of various "improvements.") - keep extraneous loads off of the programming lines - keep lead lengths short - and keep the chip power sources well filtered with capacitors adjacent to the PICAXE.

If using a serial programming cable - try using a different model computer just to see what happens. Substitution is a time-honored troubleshooting technique.

Ensure a good solid low resistance ground connection to both the power source and the serial port (or USB to serial adaptor.)

A battery operated power supply with fresh batteries is a good troubleshooting tool to substitute for a fixed supply on the PICAXE bd. Also - a variable output supply that might be tried at various voltages below 5V is a helpful tool in an attempt to match the logic thresholds of the programming line to the PICAXE input.

Finally - use a storage oscilloscope (with a high impedance probe) to look at the actual signals being delivered to the PICAXE programming circuit. Note that slow (low bandwidth) scopes may or may not catch particular problems with the programming signal waveform. But they're better than nothing.

_

Is there somewhere an "ultimate" list of helpful hints on this topic - one that has incorporated all of the various suggestions for solving programming difficulties? Or is it still rather piecemeal and spread around in various threads about the site?

 

[courchaa]

This is just a reminder to all that the voltages and current sourcing characteristics of various serial port drivers and USB port devices varies and may not be sufficient for all situations.

From years of experience I can tell you that chip manufacturers do not always produce devices that meet the defined standards - while hoping that the manufacturers of the devices they are communicating with do. Question the source of the programming signal - even if it works properly with some other PICAXE versions it may well be borderline in its operation with others.

There have been many other threads on this topic but here's another list of possibly helpful hints for programming problems:

Follow the Rev. Ed. instructions to the letter (don't make any assumptions about the functionality of various "improvements.") - keep extraneous loads off of the programming lines - keep lead lengths short - and keep the chip power sources well filtered with capacitors adjacent to the PICAXE.

If using a serial programming cable - try using a different model computer just to see what happens. Substitution is a time-honored troubleshooting technique.

Ensure a good solid low resistance ground connection to both the power source and the serial port (or USB to serial adaptor.)

A battery operated power supply with fresh batteries is a good troubleshooting tool to substitute for a fixed supply on the PICAXE bd. Also - a variable output supply that might be tried at various voltages below 5V is a helpful tool in an attempt to match the logic thresholds of the programming line to the PICAXE input.

Finally - use a storage oscilloscope (with a high impedance probe) to look at the actual signals being delivered to the PICAXE programming circuit. Note that slow (low bandwidth) scopes may or may not catch particular problems with the programming signal waveform. But they're better than nothing.

_

Is there somewhere an "ultimate" list of helpful hints on this topic - one that has incorporated all of the various suggestions for solving programming difficulties? Or is it still rather piecemeal and spread around in various threads about the site?

John,
thanks for the advice - will implement all your recommendations and see how I get on next week.

Technical - the resistors are present at all times - they are in a small download box I made with stereo jack and v small pcb - never had a problem with this arrangement in the past (to program 18A, 18X, 18X2, 28X2 etc)

 

[John West]

courchaa:
Just so we're clear regarding your reply to Technical - the 2 resistors are always in circuit - not just during programming attempts?