Shop OBEX P1 Docs P2 Docs Learn Events
C3 - Power vs. Programming question — Parallax Forums

C3 - Power vs. Programming question

Paul Sr.Paul Sr. Posts: 435
edited 2011-01-14 14:24 in Propeller 1
Finally got some time to look into the C3 and one thing has me a bit surprised:

Caution: do not connect to USB and external power at the same time

So, one must unplug the external power every time you want to reload code to the C3 - true????

Comments

  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2011-01-14 06:20
    I'm running mine on USB all the time with the idea of putting power on it only if it were moved to a "finished" project state. (unlikely in my case)

    OBC
  • ElectricAyeElectricAye Posts: 4,561
    edited 2011-01-14 06:23
    Paul Sr. wrote: »
    Finally got some time to look into the C3 and one thing has me a bit surprised:

    Caution: do not connect to USB and external power at the same time

    So, one must unplug the external power every time you want to reload code to the C3 - true????

    I've been wondering about this, too. It seems to me that this is a PITA if you are trying to debug code while testing a device. There is this thread from a couple days ago, but I don't understand what it all means:

    http://forums.parallax.com/showthread.php?128699-C3-power-and-USB-usage
  • Paul Sr.Paul Sr. Posts: 435
    edited 2011-01-14 07:06
    Thanks for pointing me to that post. Interesting!

    What it means to me: Plugging in USB and External power may or may not destroy your C3 and/or PC. Do so at your own risk and if you blow things up, it's on you.
    ElectricAye wrote: »
    I've been wondering about this, too. It seems to me that this is a PITA if you are trying to debug code while testing a device. There is this thread from a couple days ago, but I don't understand what it all means:

    http://forums.parallax.com/showthread.php?128699-C3-power-and-USB-usage
  • schillschill Posts: 741
    edited 2011-01-14 07:20
    I think the main things you should take from the other thread (that I started) are:

    1) It's probably ok to have both connected at the same time - but you are doing so AT YOUR OWN RISK.

    2) It's unlikely that you would damage the C3. If anything is damaged, it will be the computer but this is unlikely for a modern computer. It will probably be the USB chipset or interface and not the entire computer (but this is not good if it's on your motherboard or you are using a laptop).

    3) Use a hub between your computer and C3 and don't worry about it. This is what I will be doing if I want both connected at the same time. I usually try to do this anyway when playing with exposed circuit boards connected to the PC by USB.

    Other topics in that post cover modifications that can be made to the C3 (and may be in a later version ?) to avoid this issue. But, they may create other issues as well.
  • JT CookJT Cook Posts: 487
    edited 2011-01-14 09:57
    I think the component that would get damaged is the 5v regulator on the C3, but I am not 100% on that.
  • Ken GraceyKen Gracey Posts: 7,401
    edited 2011-01-14 10:38
    schill wrote: »
    I think the main things you should take from the other thread (that I started) are:

    1) It's probably ok to have both connected at the same time - but you are doing so AT YOUR OWN RISK.

    2) It's unlikely that you would damage the C3. If anything is damaged, it will be the computer but this is unlikely for a modern computer. It will probably be the USB chipset or interface and not the entire computer (but this is not good if it's on your motherboard or you are using a laptop).

    3) Use a hub between your computer and C3 and don't worry about it. This is what I will be doing if I want both connected at the same time. I usually try to do this anyway when playing with exposed circuit boards connected to the PC by USB.

    Other topics in that post cover modifications that can be made to the C3 (and may be in a later version ?) to avoid this issue. But, they may create other issues as well.

    Our internal engineering discussion is identical to schill's conclusions above. Our primary concern is damaging PC motherboards, not the C3. If you damage the C3 that's okay - we'll replace it for you.

    Ken Gracey
  • SapiehaSapieha Posts: 2,964
    edited 2011-01-14 10:43
    Hi Ken.

    THAT was most appreciated answer from Parallax end.



    Ken Gracey wrote: »
    Our internal engineering discussion is identical to schill's conclusions above. Our primary concern is damaging PC motherboards, not the C3. If you damage the C3 that's okay - we'll replace it for you.

    Ken Gracey
  • ElectricAyeElectricAye Posts: 4,561
    edited 2011-01-14 12:25
    schill wrote: »
    ...
    3) Use a hub between your computer and C3 and don't worry about it. This is what I will be doing if I want both connected at the same time.....

    So is everyone in agreement that this is the safe way to do this?
  • AndreLAndreL Posts: 1,004
    edited 2011-01-14 12:40
    I tested the C3's powere design on 40 systems; 20 PCs including laptops and MACS and XBOX 360!!!, and 20 different hubs, USB powered and externally powered and hot plugging unplugging both supplies randomly. Never a problem, and I have 1000+ Chameleons in the wild with the same design. I use it with both supplies at the same time. The only concern here is that, since we are drawing power from the USB and can draw a lot of it, its possible under a 1 in a million set of conditions to damage a motherboard maybe. Its never happened in 1+ years, and 1000 units with people using my Chameleons (same power design) where I SUGGEST and ENCOURAGE them to use both supplies. But, Parallax has a more cautious position due to some experiences with another design that used USB power, and just wants customers to be careful. So, as the designer, I am saying, its fine, I tested it thoroughly for over 1 year and 1000 customers have the design in hand, not a single USB popped. But, Parallax error'ed on the safe side and we put the disclaimers in the manual.

    That said, I personally, would use a HUB if you are going to draw a lot of power, and or be hooking things up to power and have shaky hands and might short out the USB power :) Why put your PC thru that? So $5 hub makes everything safe. But, right now -- I have my C3 powered directly from my PC, and external power at the same time -- I am pulling the external power, putting it in, out, in, out -- nothing :) NOw, I am pulling the USB power, not a glitch, now putting it back it, the C3 resets in this case USB does that as it re-scans the port, and poof here's donkey kong again --

    So -- that's the deal.

    Andre'
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2011-01-14 12:49
    Ah, so you think you can play a little Donkey Kong now that the job is done huh?? :)

    Thanks for this Andre. I had mine plugged into both most of the first day before these threads surfaced.. so 1001+ now. :)

    OBC
  • Al BoothAl Booth Posts: 137
    edited 2011-01-14 13:02
    @ElectricAye,

    I don't believe that I agree with that statement. It should be a "powered" USB hub to isolate the USB devices from the PC power.

    Al
  • AndreLAndreL Posts: 1,004
    edited 2011-01-14 14:24
    The point electric eye is making is that these are not iPhones, they are dev kits and people are going to soldering to them, experimenting etc. So, me personally, if I know I am going to be doing a lot of high current stuff then a powered hub is not only a good idea, its required. Also, I have definitely overcurrented my PC USB purposely during testing and a few others to see the results, and all did what they were supposed to do, reset the PC, all good to go. However, I just don't like doing that. So, I think the general idea is that if you are going to play with any USB powered device and DRAW high currents, why use your PC directly, might as well use a $5 powered hub for a little protection. That's all -- just good common sense. Then you will never pop a USB port. Its like if you drink and drive sooner or later you are going to get in an accident, so either don't drink or don't drive, problem solved :)

    Andre'
Sign In or Register to comment.