RS232 download cable doesn't see 20M2

[Armp]

I've set up a basic 20M2 breadboard to use a 'real' com port. I used the enhanced download circuit with the schottky clamp. (good practice ). 3 fresh AAs in battery pack, no connections to any pins other than 1,2,19 and 20.

However all attempts to download a program have failed with 'Hardware not found on Com1'. Hmm. (yes it is com1)

So checked the voltages at pin 1 (4.88v) and pin 20 (0v) .
I ran the LED test, got -0.2V and 5.36V - about as expected?
Ran the serial loopback - that was ok.
Stuck a scope on pin 2. 0V went to 5v for ~5 secs when I hit 'program'
Put scope on serout - 0v. No activity at all during 'program'.
Measured current from battery pack, 0.16ma - seems very low?

Swapped in another unused 20M2 - same results... Didn't risk the third and last.

I'm supposed to demo how easy this is tomorrow!!!!

This is the first time I've tried a real port, I must be missing something but d@mned if I know what it is??

 

[cdngunner]

Hard reset????

OPTIONS>>>>>SERIAL PORT>>>>>>SHOW PORT HELP TOOL>>>>>>>scan for USB cable

 

[nick12ab]

Have you got a decoupling capacitor and a bulk capacitor? Use 100nF for decoupling and try 47,000nF for bulk electrolytic.

 

[hippy]

Measured current from battery pack, 0.16ma - seems very low?

That does seem low but 1.6 might be right so double check meter setting / reading.

Do you have any 08M2 or 14M2 you know work or try dropping the 20M2 into a working 08M2 or 14M2 board.

 

[nick12ab]

If they're fresh PICAXEs, then you can check that they're still alive by pressing [F8] to open the terminal (4800 or 9600 baud) and see if the hello message appears.

 

[Armp]

Thanks for all the quick replies.

I did several hard resets on each 20M2 during the earlier attempts.
I do have 50uF, and 0.1uf. No sign of any noise on the scope.
Yup - confirmed it is 0.16mA.

Fired up the terminal - no message, but now I get 'serial port error - port not present or already in use' ???

Unfortunately my trusty USB converter has been requisitioned (sp?) for the next few days.

 

[Armp]

If they're fresh PICAXEs, then you can check that they're still alive by pressing [F8] to open the terminal (4800 or 9600 baud) and see if the hello message appears.

Nick- If I just have the 20M2 with pin 2 pulled down, and power applied - should I expect to see activity at serout? I've never noticed a 'hello' msg, but then I'm normally reusing chips, not new ones.

 

[Goeytex]

So checked the voltages at pin 1 (4.88v) and pin 20 (0v) .
I ran the LED test, got -0.2V and 5.36V - about as expected?
Ran the serial loopback - that was ok.

OK so far ...

Stuck a scope on pin 2. 0V went to 5v for ~5 secs when I hit 'program'

Set your scope to 1ms per division and try again. You should see pulses. Make sure trigger level is at about 2v.

Put scope on serout - 0v. No activity at all during 'program'.

Same as above. You should be seeing some pulses.

Check that the ground from the serial connector "Phono Jack" is tied to Picaxe 0v.

 

[Armp]

Nope I see no pulse at all on either serin or serout....

All wires are checked - I've just rebuilt it for the 3rd time!

As I asked Nick, if I have a bare, new 20M2 with just power applied, and pin 2 pulled down
wouldn't I see the hello stream on serout on the scope?

Can't really believe that a batch of 3 new chips can all be bad! Got to be something stupid staring me in the face...

I'm ready to give up for tonight, and have a beer.

 

[Goeytex]

Yep,

Not likely that there are three bad chips. You can always them using your AXE027 ....

 

[John West]

It sounds like your serial port is not turned on in Windows. Does the serial loop-back routine run within Windows? (I don't know.)

 

[inglewoodpete]

A few things to check:

• Is the cable an AXE026 or some other source?
• If not an AXE026, is it wired correctly? There are several "standards".
• When running the test with the PICAXE, does the actual SI pin on the chip go high and low?
• If the SI pin on the actual chip goes high and low, does the SO pin send bursts when the SI pin is high? (Can be detected with or logic probe or LED-with-resistor)
• With the SI pin held low, does the SO pin send data (Can be detected with or logic probe or LED-with-resistor)
• Erm...is the power connected the correct way around?

What is the source of the PICAXEs? Or should I ask, are they marked "PICAXE 20M2"?

 

[Armp]

The cable is a homebrew that's been used to talk to GPS receivers for a long time.. 3 wires, Gnd, TX and RX go to a 3pin header. Raw data out is +/- 12V.

I do not have any other wires looped on the DB9 - it shouldn't need any for 'no handshake'. But does PE need them??

I'm still concerned about the low current draw, and lack of any activity on serout. As I asked before "If I have a bare, new 20M2 with just power applied, and pin 2 pulled down wouldn't I see the 'hello' bitstream on serout on the scope?"

The chips are a pkg of 3, marked PICAXE-20M2, date code 1115HDG. Bought from Pete Anderson, shipped on antistatic foam and not opened until yesterday. I have a antistatic bench and wriststrap here in the lab.

I think I've already covered the other questions?

All very strange! Looks like I have to wait until I get the USB converter back.

 

[nick12ab]

Programming Editor doesn't require any additional handshaking signals.

Regarding your success with the loopback, as the serial in and serial out connections share a ground inside the PC, the loopback test will succeed even if the ground pin is not connected properly inside the serial connector. You have stated that the LED tester succeeded but test the ground connection anyway.

Does the download work if you re-assemble the circuit on another part of the breadboard? Does the download work if you don't use the enhanced download circuit? Is the diode in the enhanced circuit connected the correct way round? Have you tried some 08M2s, 20X2s and 14M2s?

 

[hippy]

I do not have any other wires looped on the DB9 - it shouldn't need any for 'no handshake'. But does PE need them??

No, just those three.

I'm still concerned about the low current draw

It does seem low. Perhaps check that all connections are made, that it's not one of those breadboards which doesn't have all +V or 0V sections linked internally, check with fresh batteries.

Add a 1K across Leg 1 and Leg 20; does the current increase as it would be expected to ?

Perhaps try another breadboard.

and lack of any activity on serout. As I asked before "If I have a bare, new 20M2 with just power applied, and pin 2 pulled down wouldn't I see the 'hello' bitstream on serout on the scope?"

I believe that's so.

With cable disconnected, Leg 2 ( Serial In ) tied to +V ( rather than 0V ), every power on should see some brief activity on Leg 19 ( Serial Out ) regardless, and that should be observable as a flash with a LED+R to 0V.

Looks like I have to wait until I get the USB converter back.

Or try with other known working hardware as suggested.

 

[Armp]

I spent another couple of hours on this problem this weekend, including using my 2 known good USB dongles, and a second breadboard - and no sign of life from any of the 3 new 20M2s.... I have 'scoped everything, all looks fine.

Put 4.7K between Pins 1 & 20 as Hippy suggested, current went from 0.16ma to 1.24ma. About right.

I'm stumped! Unfortunately I have no other known good parts on hand.

It's looking as if these are 'bad' even though they have the 20M2 marking and came from an official supplier...

Any other thoughts?

 

[Goeytex]

Mail one of them to me and let me try here. It's not likely that you can get a refund from any supplier anyway and if so the shipping would likely cost more than the value of the chips. Send me A PM if interested. Ill send them back dead or alive.

 

[jtcurneal]

Armp:

I use 20M2s here in a few projects.
Being practically next door to you, I could test one or more of your chips if you want.
Send me a PM if you want to discuss anything about testing some.

Joel

 

[Armp]

Hopefully resolved

Confirmed as bad chip batch. Replacements should be here in a couple of days.

 

[pha555]

In early Aug, 11, a customer returned a -20M2 and I verified a defect. I thought I had recovered all that I had sold, about 20 devices, but apparently not this customer.

But, to put this in perspective, this was a unique experience in ten years and was limited to 20 +- devices in Aug, 11.

Peter Anderson
http://www.phanderson.com/picaxe/