BS2pe OEM off a 3.3V supply?

Helen C

Hi,

Is it possible to run the BS2pe OEM off a 3.3V supply?
I have been looking at the SX48 chip spec sheet at it seems to run off 3.3V as does the EEPROM chip.· Is there any reason why this is not possible?

Cheers
Helen

Chris Savage

Helen,

The BS2pe MOBO could run from 3.3V, however the BASIC Stamp Module version cannot. While the SX chip used is capable of this, the firmware is set to detect brownout at 4.2V, causing a reset below that voltage. I hope this helps. Take care.

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Chris Savage
Parallax Tech Support

Helen C

Hi Chris,

Thanks very much for the quick reply.· I thought that there must be a reason.· Is it possible to get a version with the firmware brown out changed to say 3V?

Cheers

Helen

Chris Savage

Not with the modules, however if you were integrating the BASIC Stamp into an OEM design you could, in theory, install the interpreter with a smaller voltage brownout detector and get the same results. You would just have to make sure your EEPROM supported this voltage and had consistent timing as if from 5V.

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Chris Savage
Parallax Tech Support

allanlane5

That's remarkable, implying (as it does) that the CUSTOMER could "install the interpreter" in their own chip, changing the brown-out detector setting as they do so.· But maybe I'm misunderstanding this part.

Since I thought "the interpreter code" was the most jealously guarded Parallax secret -- only available in an "OEM" chip pre-programmed by Parallax, with the "hide" fuse set.

A more likely scenario (it seems to me) would be to request Parallax to create some OEM chips with the lower brown-out setting. I wonder how many they'd have to sell to make it financially worth it? Do they program OEM chips one-by-one now?

Tracy Allen

Also my OWL2pe uses an OEM special BS2pe chip with the brownout set at 2.6 volts, also as 32 i/o instead of 16. Parallax does maintain control of the interpreter, and they sell me those chips in trays (250 to a full tray) preprogrammed with my small variant of the normal BS2pe that they kindly keep on file. My understanding is that they do not offer small lots of special programming for the good reason that it is very hard to track and support these variations.

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Tracy Allen
www.emesystems.com

Chris Savage

Allan,

I guess that was a loaded response and I took for granted that not everyone noticed or knows of the current changes in the modules. The brownout detector on the BS2 has always been external. For consistency and to ensure extended temperature range considerations, the brownout detector has been moved external on all other models of BASIC Stamp as well. This means the firmware does not dictate the brownout setting. As I was getting at earlier though, you need to be sure that the voltage change doesn’t affect anything else such as timing of the EEPROM, etc. I think it is also possible for the resonator drive to be somewhat affected. This may only affect the temperature range that the device will operate in, however since it is done on the MOBO there is one example.

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Chris Savage
Parallax Tech Support

Phil Pilgrim (PhiPi)

Chris Savage said...
For consistency and to ensure extended temperature range considerations, the brownout detector has been moved external on all other models of BASIC Stamp as well.

I assume the SX48 on the MoBo is an exception to this, though, since its design still relies on the internally-programmed brownout detector. Um, right?

-Phil

Tracy Allen

Phil,

A couple of years ago I found that the problem with low temperature operation on the SX based Stamps could be traced to the brownout detector, and specifically to the BOR42 setting. The BOR26 setting does not exhibit the problem, so the MOBO should be quite safe. I did extensive testing in an LCO2 chamber using both Stamps and SX chips at that time to evaluate and resolve this problem. Also asked John Barrowman and Jeff and Chip for help. With the BOR26 setting, it works down to -65 degC (limit of chamber). I have to assure operation of my OWL2pe to -40 degC for some customers.

For general information, the problem with the BOR42 happens at somewhere with chip to chip variation in the neighborhood of -5 to -25 degC. There is an interaction with the clock setting, so the problem is less pronounced on the BS2p, but it still happens, at a lower temperature bracket. It is not a matter of the clock oscillator stopping or failing to start. The chip just goes off into never-never land and stops executing code. I think Parallax is playing it safe, and making for consistency and opening up 3.3 volt possibilities for others by using the external brownout. They now have a very nice environmental chamber on site for testing, and I see that more of the modules are being advertised for extended temperature operation. I think Chip made a very careful design of the brownout detector for the Propeller.

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Tracy Allen
www.emesystems.com

Post Edited (Tracy Allen) : 7/31/2008 8:18:48 PM GMT

Chris Savage

Phil, the MOBO has 5V or 3.3V selection on-board, but I believe you are correct in that the firmware on that module is different. But if you purchase an interpreter chip from us it will require an external brownout detector.

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Chris Savage
Parallax Tech Support

Phil Pilgrim (PhiPi)

Thanks, Chris. 'Just wanted to make sure nothing got changed inadvertently, since the MoBo depends on the BOR26 setting being programmed in.

And thanks, Tracy, for the extra details. Your tests with the BOR26 setting are certainly reassuring!

-Phil

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'Still some PropSTICK Kit bare PCBs left!

allanlane5

Well thank you, Chris, I hope I wasn't too snarky there. It IS good to find out that the brown-out setting is external to the processor.

RobotWorkshop

If you want to run the OEM version of the surface mount BS2p40 chip at 3.3v I have a blank board that can be used to make a 3.3v version of the BS2p40 stamp. I have built one of these and it works great. The blank PCB is $7.95 plus shipping. It is similar to the SX48 OEM PCB board I made up a while back.

Robert