BASIC Stamps run at 3.3V? BS2px 3.3V

Comments

• Peter Verkaik Posts: 3,956

  2009-12-22 22:16 edited 2009-12-22 22:16

  Use a spinstamp instead of bs2sx. The spinstamp runs at 3.3V
  
  regards peter
• BrooksL Posts: 17

  2009-12-22 23:13 edited 2009-12-22 23:13

  Peter,
  
  The SpinStamp is the Propeller chip. I don't mind over-kill processing capabilities at a lower cost, but different language and development environment... not so good.
  
  The 3.3V request is to decrease power requirements of the entire design BS2px, peripheral devices and all, with minimal code porting issues.
  
  The higher speed request is to increase performance to afford windows of sleep-time in the application's code.
• $WMc% Posts: 1,884

  2009-12-22 23:40 edited 2009-12-22 23:40

  BrooksL
  
  The BS2 wont run at 3.3v because of the reset supervisor chip on board, But the BS2SX might. I think if it did it would be pretty close to the edge of browning out.
  I take it Your looking at a battery powered App.?
  
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  The Truth is out there············___$WMc%___···························· BoogerWoods, FL. USA
• BrooksL Posts: 17

  2009-12-23 01:17 edited 2009-12-23 01:17

  $WMc%,
  
  On the BS2px, the brown-out detector (brown-out is really a misnomer because brown-outs are supposed to be distiguishable from power-outs) is in the SX48BD device and it's threshold is programmed by two bits in the FUSEX register.
  
  Yep, it's a battery powered app and I'm hoping to find someone who can affirm this track will probably work rather than be a dead end.
  
  Ooh, can I reprogram just the FUSEX register, or do I need the Parallax BS2px source for the SX48BD??
  -- BrooksL
• Phil Pilgrim (PhiPi) Posts: 23,514

  2009-12-23 02:09 edited 2009-12-23 02:09

  The MoBoStamp-pe will run at both 5V and 3.3V. This is because the onboard BS2pe chip (SX48) has been programmed with a lower brownout voltage. In a way, it does have intermediate capabilities between the traditional BASIC Stamps and the Prop, since it has two onboard coprocessors that can offload mundane and/or time sensitive tasks from the Stamp.
  
  Since the SX48-based Stamps have their security bits set, I doubt you'd be able to reprogram the BOE without also erasing the PBASIC interpreter. IIRC, there are also some issues with the EEPROM timing that need to be addressed at the lower voltage.
  
  -Phil
• Tracy Allen Posts: 6,667

  2009-12-23 17:59 edited 2009-12-23 17:59

  The most recent PS2p, rev E with firmware 1.7, uses an external reset/brownout chip and disables the internal BOR setting of the SX48 chip. Therefore with a BS2p you could conceivably change out the 3-pin brownout detector to make it 2.6 Volt instead of 4.2 Volt. And either either supply 3.3 Volts to Vdd, or swap the LT1121A voltage regulator for the 3.3 Volt version. The EEPROM would probably work okay, but among other caveats are the potential timing issues that Phil mentioned. (The external reset chip allows the BS2p to operate down to -40 Celsius).
  
  However, the above does not apply to the BS2px module. It still uses the SX48's internal BOR42 setting, and there is nothing you can do about that.
  
  BrooksL said, "The higher speed request is to increase performance to afford windows of sleep-time in the application's code." Another consideration is the device reset timer setting in the FUSEX register of the SX48. All the Stamps _except_ the BS2pe use the DRT=11 setting, which gives an 18 millisecond delay on wake up from SLEEP. The BS2pe uses DRT=10, which makes the delay almost 2 orders of magnitude less, 0.25 millisecond. The consequence is that the BS2pe can wake up from SLEEP, do useful status checks, and go back to SLEEP during the time the other Stamps would still be lying in bed doing nothing but at full power. That makes the 'pe more able when it comes to short sleep-wake cycles.
  
  The MOBO Stamp and also my OWL2pe data loggers are based on the BS2pe with 2.6 Volt BOR setting (which allows operation to -40 degC), and also the 0.25 ms DRT setting for more efficient sleep/wake cycles.
  
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  Tracy Allen
  www.emesystems.com
• BrooksL Posts: 17

  2009-12-23 19:02 edited 2009-12-23 19:02

  Tracy, - and Phil,
  
  Thanks, this is getting good now! I ran into your OWL web page a few months ago. I need to stay in the 24pin form-factor; so, the MoBoStamp-pe is out.
  
  I looked at the 24FC128 EEPROM and don't see the problem you suggest; it appears the 24FC can still hit the 1MHz clock rates as long as it's VCC >2.5V.
  
  Thanks for the mention of the DRT bits; I saw those but hadn't made the connection between those and the sleep wakeup delay.
  
  So, it sounds like a 3.3V BS2px mod is doable except for the security bits set in the SX48BD. Do you think Parallax would trust enough to provide the existing .HEX file for modification?? [noparse]:)[/noparse]
  
  -- BrooksL
• Tracy Allen Posts: 6,667

  2009-12-23 19:22 edited 2009-12-23 19:22

  Don't even dream that Parallax would supply the HEX file for modification. You could ask about a BS2px-IC programmed chip especially for you, but don't get your hopes up for that either. Specials like that seem easy looking from the outside, but they can be a real headache for a company. I do think your best bet in the 24 pin format would be a hack of the version E BS2p24-IC. I don't know what exactly is your need for speed vs low power drain, but the BS2p might come off favorably on that axis compared with the 'px.
  
  The EEPROM issue has to do with setup times, not with clock speed per se. My guess is that it would not be a problem at 3.3. It is your hack though, and you are on your own!
  
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  Tracy Allen
  www.emesystems.com
• BrooksL Posts: 17

  2009-12-23 21:12 edited 2009-12-23 21:12

  Serial EEPROM timing at 3.3V does not appear to be an issue - so long as the stamp in question is using the Microchip 24FC128 - for which all the shorter setup/hold/clock timings are valid with VCC >2.5V
  
  So, what would really be nice is a BS2px-e product - that runs 3.0~5.5V Vdd, 32~40MHz, DRT=10, with on-board 64Kb 1MHz SPI RAM and native PBASIC instructions to access the RAM. That should be an easy turn to production....
  
  -- BrooksL
• $WMc% Posts: 1,884

  2009-12-24 00:59 edited 2009-12-24 00:59

  BrooksL
  
  
  "So, what would really be nice is a BS2px-e product - that runs 3.0~5.5V Vdd, 32~40MHz, DRT=10, with on-board 64Kb 1MHz SPI RAM and native PBASIC instructions to access the RAM. That should be an easy turn to production...."
  
  It's hard to answer production questions on a forum.
  
  But maybe Santa is looking at these forums and can help? If Santa does answer back, Please ask Him about My 4.0GHz BS2 I've been asking about for years now.
  Thanks
  
  Just Kidding: Merry Christmas/happy holidays
  
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  The Truth is out there············___$WMc%___···························· BoogerWoods, FL. USA
  
  Post Edited ($WMc%) : 12/24/2009 1:13:05 AM GMT
• Phil Pilgrim (PhiPi) Posts: 23,514

  2009-12-24 03:11 edited 2009-12-24 03:11

  When I was developing the MoBoStamp-2pe, I was also hoping to introduce a -2p version, so I included a hybrid pad layout to accommodate both 8MHz and 20MHz resonators. But the -2p version could never be gotten to work at 3.3V, even with special firmware and even though it worked fine at 5V. The problem was with the EEPROM timing. For this reason, I wouldn't hold my breath on getting it to work with just a brownout detector change. OTOH, that was more than three years ago, so a change in firmware versions, along with a newer EEPROM may just be the ticket to success. Bottom line: try it, see if it works, and report back.
  
  Frankly, though, I consider the BS2pe to be the king of the BASIC Stamps in terms of features and speed vs. power consumption. I've never really regretted not having a MoBoStamp-2p to offer.
  
  -Phil