Conector with 6.4v between tip and center

idarwin

New Member
Hello! I'm having an issue using a TRENDNET TU-S9 (prolific chip) USB to RS232 adapter.

I'm able to read the firmware of the chip, but I cannot download any data.

The loop test pass perfect.

When I do the voltage test, it reads -6.4v with the led off and 6.4v with the led on. I removed the cable (self made), and I'm having the same readings directly on the DB9 connector.

Are these values acceptable for PICAXE 08M2?

I disabled mouse detection on the port, and USB serial number, UART and the problem persists.

Thank you all in advance.
 

hippy

Technical Support
Staff member
When I do the voltage test, it reads -6.4v with the led off and 6.4v with the led on. I removed the cable (self made), and I'm having the same readings directly on the DB9 connector.

Are these values acceptable for PICAXE 08M2?
RS232 from a PC is usually -10V to 0V ( LED off ) and 0V to +10V ( LED on ), and the official spec goes further, so the signals should be okay for an 08M2 with the two-resistor download interface in place.

If you can read the firmware code then it should be able to download. It may depend on what program the chip is already running so a Hard Reset might be the fix. Power off the PICAXE, initiate a download, then, a second or so later, turn the power to the PICAXE back on.
 

idarwin

New Member
Thank you! I tried the hard reset but I get the same response:

Verification error - 0x00 transmitted but nothing received at byte 0.

I also tried to clear the program; same result.

I'm using a fresh 9v battery, and I measured the 7805 and it's a perfect 5v.

I've seen the same issue in older posts, but I could not find a solution for this. I thought the problem were the 6.4v on the RS232.

Any other ideas?

Thank you again!
 

Goeytex

Senior Member
Verification errors are usually voltage related.

If the loopback test passes then there is likely nothing wrong with the adapter.

First, I would remove the Picaxe from the board or socket and check to make sure that none of the pins are folded under. Especially the Ground pin.

Then I would suggest doing the voltage test again but this time connect everything up and measure the voltage between the Picaxe 0V pin and the Picaxe serin pin. Measure directly on the pins. You should see ~5V when the LED is ON and ~0V when the LED is OFF. This will test that the download circuit is correct and should verify that the ground from the stereo jack is common with the Picaxe chip.

While you are at it, measure the voltage between the Picaxe 0V Pin and the Picaxe V+ pin. Again measure directly on the pins, nowhere else. If this is not correct then there is likely a wiring/grounding issue.

I suspect there may be a bad ground connection somewhere between the stereo jack and the Picaxe or that the Picaxe itself has a bad ground. Also the stereo plug may not be fully seated into the jack. This has bitten me several times.

Goey
 
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Technical

Technical Support
Staff member
Your power supply is almost certainly collapsing, 9V PP3 batteries are not designed to drive 5V regulators. Make sure you have, for instance, 100nF and 100uF capacitors both side of the regulator (between the power rails and ground).

Or simply power the whole circuit from 3xAA cells instead and see if it works then.
 

idarwin

New Member
Hi! sorry I was delayed by my job; thank you all again for your help.

So here is what I did:

1) I replaced the 9V battery with a 12v 1A PSU
2) Using my multimeter I measured the voltage regulator and PICAXE socket without the chip and got a 4.34v reading (don't know if that's enough)
3) Re seated the chip with this configuration and tried again; but I got the same error when downloading the program.

Neither the PICAXE nor the voltage regulator get warm in any way.

The board I'm using I bought it online several years ago and never used it; maybe next step would be to debug the board and also test for a short on the stereo jack.

Edit: I can confirm the board has a 32k resistor on pin two.

Best.-
 
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Goeytex

Senior Member
That should be a 22K not a 32K and there should be a 10K as well.

With a 12V supply and a 5V regulator .... 4.34V is not good. It should be somewhere between 4.95 and 5.05 V. This may indicate a problem on the board or with your wiring or possibly a bad regulator.

Disconnect the stereo plug and anything else attached to the Picaxe Board except the power connections and measure again. Is it still 4.34V ? If so then there is most likely a power problem unrelated to the stereo adapter.

If the voltage is between 4.95V and 5.05V with the stereo plug "unplugged" then the fault lies somewhere between the stereo socket and the PC.

Possible Faults:
1) Bad or missing Ground
2) Incorrect wiring
3) Bad regulator

Where is the regulator located? On the board or externally on a breadboard ?
Is the regulator ground connected to the Picaxe Ground?

ALL grounds MUST be connected together. This includes the 12V ground, the regulator ground, the board ground, the Picaxe 0V Pin, and the PL adapter ground when plugged in.

If you cannot locate the fault, then take a clear photo of the entire setup and post it here so we can have a look.
 
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PhilHornby

Senior Member
I'd strongly recommend you invest in one of each of these :-

PICAXE USB Download Cable
BreadBoard Adapter

I realise they could be considered expensive 'for what they are' - but you need some reliable foundations, upon which to base the rest of your experiments.

Being able to reliably download code to the Picaxe is a fairly fundamental requirement. :)

(Everything else, you can make up as you go along, like I do!)
 

hippy

Technical Support
Staff member
The board I'm using I bought it online several years ago and never used it; maybe next step would be to debug the board and also test for a short on the stereo jack.
Some sort of short between the Download Serial In and Serial Out pins can cause the issue you are seeing and could explain the regulator voltage being pulled down.
 
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