BASIC Stamp P40 not ID'ing

Painless

After being disappointed with an OEM BASIC Stamp P40 I purchased, I ordered the real thing from Parallax (A BASIC Stamp P40). I've wired the stamp onto a breadboard as follows:

7.5v to pin 40 (VIN)
Ground to pin 39 (VSS)
VSS & VDD were taken from the stamp to the positive and negative power rails of the breadboard for external use (nothing connected at the moment).

I also connected a serial cable:

DSR shorted to RTS at the PC
RX to pin 1 (SOUT)
TX to pin 2 (SIN)
DTR to pin 3 (ATN) with a 0.1uF cap in line
GND to pin 4 (VSS)
I also joined ATN & VSS with a 0.1uF cap

The stamp will not ID with the stamp editor tool, I get a loopback and echo response but that's it. I've verified the serial cable is good with my OEM stamp. I did note that the RES pin (38) on the stamp is only showing 200 millivolts, which according to the docs indicates that the power supply is less than 4.2 volts, however, this is not the case.

Can anyone please help me understand what's wrong here? I've double checked the instructions over and over again and can't find a mistake. I've also tried using a 7805 5 volts regulator to supply VDD (removing VIN) but with no change in results.

Thanks in advance for any help,

Russ.

dandreae

Can you take some voltage measurements?· If so, please measure:

Vin to Vss =
Vdd to Vss =
Rst to Vss =
Sout to Vss =
Sin to Vss =

Thanks,

Dave

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Dave Andreae

Parallax Tech Support·

Painless

Dave,

Thanks for your reply, here are the measurements you requested:

Vin to Vss = -7.56 v
Vdd to Vss = -4.96 v
Rst to Vss = -315 mv (I assumed you meant RES?)
Sout to Vss = 3.272 v
Sin to Vss = 9.74 v

Each measurement was taken 'black to red'.

Thanks again,

Russ.

dandreae

Hello,

Your reset seems to be the main issue here, it should read 5 volts.· Your other voltage readings seem fine except that the polarity on your meter looks like it was switched.· The readings should be:

Vin to Vss = source
Vdd to Vss = 5v
Rst to Vss = 5v
Sout to Vss = -5v
Sin to Vss = -10v

Send me an e-mail at dandreae@parallax.com and·I will see what we can do?· In the future you'll want to power the BS2p either with Vin or Vdd, not both.


Kind regards,

Dave









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Dave Andreae

Parallax Tech Support

Post Edited (Dave Andreae (Parallax)) : 4/28/2009 4:05:30 PM GMT

RobotWorkshop

Since you didn't specify the pin #'s and connector used on the PC can we assume that you are using the one posted here:

http://www.parallax.com/Portals/0/Downloads/docs/prod/schem/bs2p40SchemRevB.pdf

It sounds like you have it working with an OEM p40 chip but can't get a 40-pin BS2p40 Stamp to Identify correctly.

Are you using the latest BASIC Stamp software on the PC? Also, are you using a connection to a real serial port on the PC or are you using a USB to Serial adapter?

Robert

Painless

RobotWorkshop,

Yes, that is the schematic I was following for the PC serial connection, it is to a standard 9 pin serial port with no need for a USB adapter.

From Dave's response it seems that perhaps the Stamp is not functioning correctly. Just to clarify, I didn't attempt to power both Vin and Vdd at the same time, simply tried both methods of powering the stamp separately. For example, I tried powering Vin with 7.5v and simply taking Vdd's output (which should then be a regulated 5v) for power to future components. Alternatively, I tried using a 7805 5v regulator to feed 5v to Vdd with Vin left unconnected. I was following Page 20 of the Basic Stamp Syntax and Reference manual.

Thank you for both of your responses and time, I have just emailed Dave as requested.

Russ.

Painless

Just wanted to thank Parallax for taking care of my defective BS2P40. I received a replacement from their RMA team a couple of days ago and just got the time to test it out on my breadboard, all is working great this time.

Thanks Parallax for a quick and friendly response to my issue.

Russ.