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Red Pill or Blue Pill?

Posted: Thu May 14, 2015 3:50 pm
by Rick Kimball
If you look on the ebay site there are some red boards and some blue boards. I didn't really look closely at the differences when I ordered. I just picked the least expensive one. I ended up with one of the red stm32f103c8t6 boards. Well the fun has ended. The usb connector came loose and now it only works if I power it externally.

Looking at the differences between the red board and the blue boards ...

The red board:
Good things about the red board:
  • 1.5k pull up resistor on the PA12 pin (USB D+) which you can programatically drag down for automated USB reset.
  • large power capacitors and LDO power (AMS1117 3.3v).
Problems with the red board:
  • Silk screen is barely readable, the text is chopped off on some of the pins
  • USB connector only has two anchor points and it is directly soldered on the surface
  • Small reset button with hardly any resistance
The blue board:
blue32466.jpg (78.03 KiB) Viewed 20827 times
Good things about the blue board:
  • Four soldered anchor point on the USB connector. What you can't tell from this picture is that there is a notch in the pcb board and the USB connector sits down inside it some. This provides some lateral stability that takes some of the stress off the solder points. +2
    (Actually there are now blue pills that have a two anchor point usb connector)
  • It has nice clear readable silkscreen printing. +1
  • It also a larger reset button.+1
  • Often supplied with a 300mV regulator (rt9193-33gb)
Problems with the blue board:
  • Probably won't work as a USB device if it has a 10k or 4k7 pull-up on PA12. You have to check the pull up on PA12 (USB D+). If it has a 10k or 4k7 pull-up resistor, you will need to replace it with a 1k5 one to use the native USB.
Nice features common to both:
  • SWD pins broken out and easily connected (VCC, GND, SWDIO, SWCLK)
  • USB 5V is broken out with easy access.
  • User LED on PC13
  • Power LED
  • You can probably use more flash (128k) than officially documented for the chip (stm32f103c8t6 64k), I was able to load 115k of flash on mine and it seemed to work.
  • Both boards have the same pinouts, you can use them interchangeably
Problems with both boards:
  • No preloaded maple bootloader * to me this isn't really a problem as the entire 64k of flash is available for use. Also, every chip provides a factory ROM based serial boot.
  • No user button
If people have any more comparisons or comments, please post on this thread.

Another style BluePill (note: pinouts valid for both Red and Blue boards)
bluepillpinout.gif (142.14 KiB) Viewed 15037 times ... iagram.pdf


Re: Red Pill or Blue Pill?

Posted: Thu May 14, 2015 4:14 pm
by JensEP
I have two blue boards where the USB is like on your red board, but the silk screen is like your blue one.

Re: Red Pill or Blue Pill?

Posted: Fri May 15, 2015 1:19 pm
by zoomx
I din't noticed how the USB connector was soldered but searching for differences in the photo that I have posted here
it seems that if you have a bad USB connector you have also a big LDO underneath.

I believe that big LDO meah high current.

Re: Red Pill or Blue Pill?

Posted: Sat May 16, 2015 8:11 pm
by strawberrymaker
But pinout seems to be the same. Compared it with the Board that i got today and it seems like it uses the same pinout. Maybe the boards were manufactured by different manufacturer and they changed it because they have f.ex. the usb port with 4 ground pins or the bigger button already in stock?

Is there a difference on the bottom side between the red and blue one? I think i've already seen some with ams1117 as an ldo instead of the sot235 one (DEA1D if i can read it right, prop not)


Re: Red Pill or Blue Pill?

Posted: Mon May 18, 2015 4:07 pm
by zoomx
See the link that I have posted for more photos.

Red and blue seems identical in functionality.

Re: Red Pill or Blue Pill?

Posted: Thu May 21, 2015 8:17 am
by RogerClark
I have the red board, and got the same problem as Rick.

I had to reflow solder the connector, both its electrical connections and also the 2 pads that hold it down ( or doesn't )

But as I knew the repairs wouldn't last, I got out my hot glue gun and completely smothered the connector and the end of the board in hot glue. I suspect epoxy resin glue would be even better, but it takes a while to set, ( even the 5 minute epoxy seems to take somewhat longer to fully set)

I'd advise anyone who has one of theses boards to put a load of epoxy over the USB connector, but make sure you don't let it ooze inside the connector.

Re: Red Pill or Blue Pill?

Posted: Thu May 21, 2015 12:36 pm
by mrburnette
A trick I have used for years is DeoxIT by Caig. Cheap USB connectors often 'stick' metal-to-metal and cause strain on the reflow joints holding the connector to the PC board. This product is the best I have ever used - not cheap, but one only uses a small amount, so it is economical over time.

I still think the epoxy or Goop overcoat is not a bad idea. If you decide to use the DeoxIT product - "small amount" means to use very little! Whatever is in this stuff is concentrated. Using a lint-free lens cleaning cloth, one can actually see the dirt and oxide come off connectors! A film applied to DIP components assure easy insertion, excellent contact low-resistance, and ease of future removal, if necessary.


Re: Red Pill or Blue Pill?

Posted: Thu May 21, 2015 9:00 pm
by RogerClark

Connector failure because of bad design seems common loads of boards that I've seen, not just stm32

Just fixing into 2 small PCB pads causes the copper pads to be pulled off the board.

Actually it could also be the quality of the whole PCB. I managed to accidentally dislodge a reset button on a Zigbee programmer board a few months ago, and had to hand solder some tracks back into place.
So perhaps the copper is not well bonded to the fibreglass

Re: Red Pill or Blue Pill?

Posted: Thu May 21, 2015 9:09 pm
by ahull
The progressively smaller and smaller features on modern PCBs don't help. There are mechanical limits to how much strain the bond between a very small track and a very small pad can take. Smaller means more fragile. Potting things in hot glue, silicone or epoxy is sometimes the only option it you want it to survive. On the plus side, potting a tiny board is far easier and cheaper than potting a large one.

Re: Red Pill or Blue Pill?

Posted: Thu May 21, 2015 9:31 pm
by Rick Kimball
Good idea @ahull. I'd like to see what one of those look like.