DavidSchoen

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• What volts can I supply the VBAT pin with?

  @DavidSchoen started

  • 35 comments
  • 18,868 views

  @Gordon replied
• What volts can I supply the VBAT pin with?

  in General • 9 years

  

  Awesome, thanks again +Gordon (especially for taking the time to humour me about figuring out what the PFET was) :)

• What volts can I supply the VBAT pin with?

  in General • 9 years

  

  Thanks +allObjects, that's way more illustrative!

  Do you know what the device between the GATE/SRC/DRN pads is? I had assumed that would be a regulator for 16V -> 5V (and hadn't yet been confident enough to supply > 3.7V to BAT_IN), but clearly it's something else and now I'm just curious :)

• What volts can I supply the VBAT pin with?

  in General • 9 years

  

  It doesn't I'm afraid (there's no 5v regulator) - the VBAT pin is battery or USB volts, so you need to be careful there. There's actually the circuit diagram of the power supply here: espruino.com/Pico

  Given this is the only big thing you thought I got wrong, I had enough confidence to wire up 10V to the BAT_IN and check it with more than just USB coming in, you are of course right :)

  I've had a look at that power diagram a couple of times, but without knowing more about how it worked I couldn't really get much out of it because the pins on it are VBAT, 5V and VDO - given they're not referenced like that anywhere else on that page it's not obvious (to me) that they were pins so I'd originally assumed this was somewhere in the middle of the circuit and hadn't realised I could easily probe any of those points.

  Given the little business card that comes with the kit, the board itself and the schematics all have different names for these pins - do you think that a section could be added to that page clarifying which pins have changed names over time and what those various names are?

• What volts can I supply the VBAT pin with?

  in General • 9 years

  

  Hi All, Thanks for all the answers.

  I've had a go at following all of the above and also spent more time following traces, probing points on the board, etc, my understanding is now as follows:

  • It's safe to power the Pico via the BAT_IN pin (aka BAT) from any DC 3.5-16V source
    
  • The VBAT pin (aka VCC or 5V) will get power from a 5V regulator
    
  • The 3.3V pin (aka VDO or 3.3) will get power through a 3.3V regulator (which is powered from the 5V regulator)
    
  • USB will always run through a schottky diode to prevent BAT_IN from giving power to USB if it's > 5V
    
    

  I think my original question was doubly confusing as I'd confused VBAT and BAT_IN (partly due to all the different names for the same pins in different places).

  Another question comes up though if I need a few 3.3V devices - the regulators according to the power section appear to be MCP1703T-3302E-CB which is rated up to 250mA - is this the correct limit for the version on the board and are there any other limits that will cause a problem first?

  Would it make sense to put as many devices on the 5V regulator (VBAT pin) as reasonable to increase efficiency / raise maximum Watts if I'm coming at all close to that limit?

  I don't think I will come close to the limit for anything I'm currently trying to solve (but I will actually test mA on each device individually now), but I'd just like to know what the best approach would be (short of introducing another regulator / external voltage follower / etc).

  Cheers,
  Dave

• What volts can I supply the VBAT pin with?

  in General • 9 years

  

  Hi,

  This may be kinda dumb, but I'd rather ask a dumb question before I break my Pico :)

  On the Pico page (http://www.espruino.com/Pico) it talks about the voltage regulator accepting between 3.5-16v and the board being happy to run on a 3.7v Lithium cell - can I use the VBAT pin for either or if I wanted to supply a higher voltage should I be supplying it via some other pin?

  So far I've been running a regulated buck converter set on 5V through a USB plug I've wired up "just in case", but I'm wondering if I can just chuck a less well regulated supply straight at VBAT?

  Cheers,
  Dave

• Getting function not found errors when uploading code

  @DavidSchoen started

  • 14 comments
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  @DavidSchoen replied
• Getting function not found errors when uploading code

  in General • 9 years

  

  What happens if you disconnect your voltage divider and connect the 3.3v pin in Espruino directly to A5? That should ensure that you have over 2.9v on A5, while not running the risk that you're over-volting it?

  This works fine :/ and now that you ask, I remember this was actually the first test I ran (i.e a wire straight from 3.3 -> A5, as a quick way to see what analogRead(...) gave).

  Depending what you're connecting to, it's possible that you're actually measuring something with an AC component? If so the volt meter may well read less than the actual peak voltage.

  I think you're probably right and you've given me a couple of good things to try out.

  I'm trying to switch a couple of devices based on the voltage in a 24V (nominally 24, in the real world 22-32V) offgrid solar system - to try to do that I'm currently testing with a cheapie Lab PSU in that range (I'm pretty sure the DC signal on this is ok) and supplying power to the Pico through a regulated buck converter circuit (this looks identical to the one using http://www.ebay.com.au/itm/181409861491) set to 5V and supplying the 5V via the USB plug. When I actually tested I was very slowly ramping up volts on the PSU (started at about 7V).

  All GNDs are common.

  I suspect if there's an AC signal getting in it might be the switching noise from the buck converter regulator.

  I'll see if I can get some time with an Oscilloscope to see if I can find any fluctuations that shouldn't be there.

  Cheers,
  Dave

  edit: many many typos.

• Getting function not found errors when uploading code

  in General • 9 years

  

  Thanks for confirming it should be right to go to at least 3.3V +Gordon.

  The troubleshooting page is where I figured out how to reflash and boot to an empty program from.

  I'm going to stick with a much bigger voltage divider gap (and less accuracy in the range I care about for now).

  I'm also getting a more accurate multimeter on the off chance that's the issue :)

• Getting function not found errors when uploading code

  in General • 9 years

  

  I'm still not worried about the code conventions at this point and more that something is going wrong at the hardware level...

  I appreciate the concern about the specific code, but it's kinda missing the point that I'm looking at some hardware problem and would really like to focus on that.