problem building an OEM BS2p40

skinnydude

I'm trying to build the BS2p40 on a custom design.· Using the schematic from this link

http://www.parallax.com/dl/docs/prod/schem/bs2p40SchemRevB.pdf

I tried to build one using these parts from parallax

PBASIC INTERPRETER CHIPS
PBASIC48W/P40

EEPROM
602-00013

RESONATORS
250-12060

also, for the PNP and NPN transistor pack, I used
DDTA114ECA
DDC114EU

Then I used the Basic Stamp Editor v. 2.2, go to run, identify and it doesn't detect it.
I get
Loopback: Yes
Echo: Yes
but nothing under Device Type nor version.

The software and cable works correctly because it can detect the Basic Stamp kit I bought, but not the one that was just designed.

Attached is my schematic.· Can anyone tell me if I'm using a wrong part number or if my design is flawed?· Thanks.

Jon M

I've had the same problem. it appears to do with the resonator timing but I can't see the reason why when I compare my design with the official one.

Any help would be very much appreciated.

Thanks

Jon Millard

skinnydude

I see you said "had."· Was wondering if you fixed it by redesigning somehow or if you still have the same problem.

K de Jong

Hi,

I see a resitor of 10k across the resonator, to my feeling that resistor may be a bit larger 1M, or so.

Regards,

Klaus

skinnydude

Parallax's schematic says to put 10k, not a meg.

Tracy Allen

I don't see anything amiss in your schematic. The oscillator should work at room temperature with just about any feedback resistor there. Have you checked for 20mhz at OSC2, or around 2.5 volts average there with a voltmeter. Also check at MCLR to be sure that ATN pulse is coming through when the IDE tries to identify the Stamp. Power supply voltage 5v okay? If it is hand soldered, check all the connections again under a microscope (I bet you've already done that at least 10 times!).

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Tracy Allen
www.emesystems.com

skinnydude

It looks like my oscillator isn't working right.· I think when hand soldering, the heat destroyed it.· I'll have to get all through hole and put a socket on it to make sure.· Hopefully I'll know by tomorrow.

mm

Change the 10 k resistor across the resonator to a 1 meg ohm and it should start working. I don't know here that 10 K resistor came from in the parallax data sheet but the Ubicom data sheet recommends 1 meg ohm.


Mike

Jason-WI

I have an older schematic of the p40 that shows a 1 meg across the resonator not 10 k. You are most likely loading down the resonator.

Jason

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He who dies with the most toys wins!

Chris Savage

Jason,

·· I believe the schematic is correct, but I will verify it with one of our engineers and post back.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

Chris Savage

Hello,

·· I confirmed today that we are, in fact, using the 10K resistors on the BS2p40 modules.· The schematic is correct.· If you're using a resonator purchased from us, the value is correct for it.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

skinnydude

apparently I had some bad 5pf capacitors.· I removed them and it works fine.· I put new ones in and it also works fine like that.· Thanks for all the input and help!