28x1 download problem

HI

I have bought a PICAXE 28X1 chip and am trying a test prg with a flashing LED. I have checked through the circuit which is on a bread board and uses a picaxe serial download adaptor board to connect the download socket to the board. When I try and down load the prg, the download screen comes up but the progress bar does not progress at all, then after approximately 20 sec a message box appears with "no hardware found on com 1". I have tried the com 1 port check in the options screen and the pin is at -0.57v when low and then goes to 5 v when high on serial in pin. This implies that the serial port is connected correctly. 0v on the serial download board is at 0v. I have a 4hz resonator connected. Reading your literature this can be fitted either way around on pin 1 and 3.

Could you please tell me what else I maybe doing wrong. If you could suggests ways to check this I would be most grateful.

Thanks a lot for your help

Most likely the download circuit on the bread board.

Carefully check the location of the resistors and the pinout of the socket on the breadboard.

Details on page 21 of getting started - Manual1

thanks.
I am using the picaxe serial socket board which is then plugged into the bread board. I have checked the continuity from the picaxe adaptor board pins to the pic pins and these work out fine. Can I have a problem in the down load circuit if the serial check works with serial in going high and low when required?

Here are some things to check.

Phil75 said:

Here are some things to check.

Click to expand...

good diagram it would be a perfect fit in the picaxe FAQ

As you can see I just copied it from the manual then added to it.

Saves a lot of explaining.

Brilliant diagram.

If I could be picky - hate to bring it up really - but while you have the magic red circle thingy out, it might be useful to include leg 8 with the other power connections.

Thanks everyone for your help. I have been using this diagram from the picaxe manual and the only thing that is different is that I do not have a reset button in the circuit. I have tied the reset high through a 4.7 resistor direct from pin 1 to pin 20. I have checked this is at 5v.
I am using a power supply with variable current which appears to be very stable at 5v.
I am using the picaxe supplied cable which I am assuming is correct.
If I have checked the serial IN in the options of the programming software, does this mean that the problem must be in the serial out circuit as I presume that this would stop the return signal to the PC and so the pc would assume no hardware fitted?

Have you ever managed a download? i.e. did it work once but not now?

A few steps in the process of elimination;
1. Try starting the download with the 5V to the 28X1 OFF. Immediately the download box comes up, turn the 5v to the 28X1 ON.
If this fixes your problem, recommend you install the reset switch as a running program can delay the chip's readiness to accept a download depending on what the program is doing.
2. The 28X1 will run without the resonator so remove the resonator (leave legs 9 & 10 open). Test with and without step 1
3. If neither of these work then there is likely to be a 28X1 or a circuit issue.
with the 28X1 powered and taking care not to short any pins, carry out the com1 port check but measure at the 28X1 pin position on the breadboard for serial in (Leg6) to verify that the PC serial out pin is in fact connected all the way to the 28X1 serial In via the 22k resistor.
Assuming you have an actual serial cable - not a USB download cable, you could verify the wiring with a meter by unplugging the cable at the PC and the removing the 28X1, and, checking the continuity between serin and out.
DB9 pin2 (PC serial out) should be connected to 28X1 leg6 (serial in) via the 22K resistor.
DB9 Pin3 (PC serial in) should be connected to 28X1 leg7 (serial out) directly.
DB9 pin5 (PC 0v) should be connected to 28X1 leg8 & 19 (0v) directly.

Trust this helps

YIPPY FOUND IT. Thanks for the last it email it helped me narrow it down to the serial download board that was supplied. For some reason there is a break in the connection to the serial out. I hard wired the center pin to the serial out pin and this has fixed the problem.
Sorry for the long delay in getting here, but I presumed that it must have been something I was doing.

THANKS FOR ALL YOUR HELP. If anyone buys the serial download read board adaptor you have problems downloading CHECK THE SERIAL OUT CONTINUITY.

BCJKiwi said:

Brilliant diagram.

If I could be picky - hate to bring it up really - but while you have the magic red circle thingy out, it might be useful to include leg 8 with the other power connections.

Click to expand...

OK, fixed that.

Tried Everything

Hi All,
I too have a 28x1 download problem. At first it was working fine, and accepted the programs and did everything it was supposed to. It was mounted in a modtronix SBC board, to which i had added the picaxe download circuit and reset circuit. no resonator. More detail here:http://www.picaxeforum.co.uk/showthread.php?t=8270

Well since then i moved up to the larger Modtronix sub board so i could could get more inputs and output connectors for my transducers and download to the Sparkfun SD card module ( a previous thread) and get time from a DS1307 clock.

Well thinks were sort of going ok, because i could download program, read data from transducers and output to the sparkfun module. I hadn't used the clock yet. It sent data back to the terminal through the download cable, and it was as expected. I was working on iterations of the code, and then one day it just would not let me download any more programs. No physical changes, it just seemed to have developed an attitude.

At first i thought i must have done something electrical, eg disturbed a faulty connection, made an imperceptible short somewhere. I started testing, removing components, tried more basic programming, and now i am at my wits end.

I have checked all the connections in the diagram in this thread with the red circles (no resonator for 28x1) and all the voltages and resistances are where they are supposed to be.

The power supply is a rock solid 5.0V from the modtronix board.

I did the serial download diagnostic as per the program, and got minus 0.5 and plus 5.5, so no probs with the serial connector.

I tried holding the reset down while attempting to download - no good.

Pressing the reset has the same effect as an attempted download without pressing reset, - they both restart the program that was last successfully loaded - happily displaying transducer output to the LCD module.

The last successful program has a SERTXD command that sends data back to the computer. when i first started having the problem i got nothing back from the chip. This led me to suspect the download cable itself, but the electrical continuity checked out fine. But now, when i open the terminal i get a bunch of gobbledigook and strange european characters with accents coming back. It is as though it is trying to talk but can't get the words out correctly. In the meantime the display of tranducer data on the LCD via I2C is uncorrupted.

I have been removing just about anything that could be removed, simplifying the circuit, simplifying the program, but i can still not download.

I tried the trick mentioned earlier in this thread, powering up when the download is attempting to commence, that didn't work.

There must be more i can do, look for, test for.

Any advice?

Whoops!

Well, me apologising again.

Here i was assuming that if the "serial port test" gave the correct voltages, an attempted download restarted it, and that at least some data seemed to be coming from the device then the serial download cable was OK. Silly me. There is a learning point here.

In frustration i had purchased a shop bought serial download cable a few weeks ago, but had no reason to use it because my home made one appeared (per description above) to test ok. Imagine my surprise when i replaced the home made one with the shop bought one and i got clear serial data back from the picaxe. And download and firmware test no problem.

It seems my home made cable had developed an open circuit in the ground wire. Despite the voltages testing OK in the serial port test, clearly there needs to be a contiguous ground connection to send and receive data. Maybe this is a diagnostic tip to add to the official Picaxe troubleshooting guide?

I will now pull my head in and post when i have a real problem or can maybe help.

Michael

Hi Michael V

Been there done that - you have nothing to apologise about. The only way to learn is to do it wrong first.

In my years of experience, both in military and civilian electronics, it is that electronics rarely fails, it's always cables and other "mechanical" type connections that give the most grief.

Even now, where I work in the Telecommunications industry, anytime I get a fault, I ignore the electronic symtoms and go straight to cables. (Especially if I made up the cable in the first place). 90% of the time thats the problem.