Download Problems at 4MHz, not at 8MHz

[Revolvr]

Having problems downloading. I get the error "Error - Memory Verification Failed (Byte XX)" where XX changes each time. Most of the time I get this error but not always.

Here's the interesting part. If I overclock the chips to 8MHz, the downloads always work.

System:
Experimenter's Board
USB-to-Serial converter cable with proper drivers installed.
Using 5.0.7 program editor.
Firmware version 9.2.

Here's what I've done to debug:
Mostly using 3 fresh AA bateries for power. Multimeter shows 4.6 volts.
Also used a 9V wall wort connected to the 7805 supply.
Doublechecked the board resistor values, positions, and touched up the soldering.
Tried both an 18X and 08M, get same symptoms on both.
Tried different host computers.
Get the same error when using the "Clear Hardware Memory" option.

None of these changes affected the results.

I am generally OK because it works when overclocked. But changing frequency is difficult and it is difficult to clear the memory. The download at 4MHz will work occasionally.

Any ideas?

Thanks,

-- Dan

 

[Revolvr]

I've isolated the problem to the USB-to-Serial adapter I bought with the PICAXE kit. It is from www.techsupplies.co.uk part num USB010 and uses Prolific drivers.

I found a laptop with a real serial port and was able to download at both speeds no problem.

So now I am looking for a USB-to-Serial adapter that actually works reliably. Can anyone recommend one?

Thanks,

-- Dan

 

[Technical]

We have sold over 50,000 of the USB010 without problems to PICAXE users and so do not believe there is a general issue with this device!

The fact that you can download at 8M but not 4M proves the adapter is working.

The symptoms do indicate an error somewhere around your 10k/22k download circuit that is providing a threshold voltage, working sometimes at some voltages/speeds and not others. We believe it is far more likely to be a soldering or power supply issue than the USB adapter.

What happens when you click the Firmware? button - does this work?

Have you tried the dedicated PICAXE USB cable - part AXE027?

Edited by - Technical on 10/01/2007 18:05:19

 

[Revolvr]

I think that last sentence on my previous post came out a bit abrasive. Apologies, guess I was frustrated.

One last thing I did to isolate the problem was to use the USB-to-Serial adapter on the computer that has the serial port. When using the adapter, downloads fail. When using the serial port directly, downloads work reliably.

Since downloading works with the serial port fine, but fails consistently using the adapter on 3 different computers, I conclude the problem is with the adapter itself. Since this is not a generic problem with the adapter or the Prolific drivers, the adapter itself must be defective. If you can think of anything else to further isolate the problem, let me know.

Clicking the “Firmware?” Button usually works.

I have not tried the AXE027 but I would like to. I’d return the USB010 but I live in the states and it would probably cost as much as a new cable to ship it back.

-- Dan

 

[BeanieBots]

A fundamental difference between using a serial port and the adapter is the output voltage level. The download circuit is designed to work with both levels which always ends up as a compromise for being ideal on either.
If you replace the 22k resistor with 1k when using the USB adapter it should be more reliable.

DO NOT USE 1k WITH A DESKTOP SERIAL PORT.

Edited by - beaniebots on 11/01/2007 07:51:58

 

[Revolvr]

Brilliant mate!

I removed the 22K, soldered 2 jumpers and tried several values from 27K down to 1K. I got the best results at around 1K. Still getting successful downloads only 50% of the time but thats much better than before.

 

[Revolvr]

For what it's worth I bought the AXE027 to try instead of the USB010. Works perfectly. The problem all along has been the USB010 USB-to-Serial adapter.

-- Dan

 

[redpawn]

I too had trouble with the USB010 cable. First use on the AXE090 board the 08M burned up (coincidence?). The board and chip had worked with the actual serial port. Tried another USB010 but it would not work with either of my computers despite happy drivers. The new cable did not hurt any chips. The second USB010 cable works with other computers I have access to. I solved my problem by using the more expensive USB2 version which I can no longer find at the site. I have had no trouble with the USB2 cable. It gets near daily use.
Bryant

 

[jplinteau]

Hi!

I'm having the same problem sometimes while downloading with the serial port.

I read :

"The download circuit is designed to work with both levels which always ends up as a compromise for being ideal on either.
If you replace the 22k resistor with 1k when using the USB adapter it should be more reliable."

Interesting !

Can you tell what are the best value for serial com ?