F405 & F411 versions of the BluePill

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RogerClark
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F405 & F411 versions of the BluePill

Post by RogerClark » Fri Sep 29, 2017 4:54 am

Update...
After evaluating the practicality of this, it does not appear to be economic to produce a F4 board, especially in in BluePill form factor.

The only devices which would fit on such a small board are the F411, which does not provide substantially more processing power than the F103, as its clock speed is only 100Mhz.

The F411 is worse than the F103 for signal acquisition, as it only has 1 ADC (the F103C has 2)

The F405 is a much better processor, but is is not available in a package that would fit on the Blue Pill form factor without using a 4 layer board.
But 4 layer boards as many times more expensive than 2 layers - some PCB plants seem to change 10 times as much for 4 layers.

The other option is to use a BGA version of the F4xx, but these parts are hard to source as they have minimum order quantities of several thousand (probably 1 reel)

And... As has been pointed out by Chris Micro, you can buy a Teensy 3.6 for $19 USD, which is also on a very small form factor, and outperforms most STM32F4 MCU's

Hence I'm going to park this, as its not worth the time and effort.



_______________________________ Original post ______________________________________


Following form a discussion with @lkcl about creating a STM32 board which is mechanically compatible with the Arduino Due,
http://stm32duino.com/viewtopic.php?f=9&t=2630
the possibility was raised of getting a F4 version of the Blue Pill made by a Chinese manufacturing house.

As the STM32Stamp Eagle design files were published several years ago. ( http://eleccelerator.com/stm32f4stamp-breakout-board/ )



I've taken these files and run them though the Eagle2KiCad converter and put the resultant files on Github

https://github.com/rogerclarkmelbourne/ ... ill_Boards

In the F405Pill folder

The current status of the files is that the PCB fails DRC because it looks like some vias are not connecting to the filled GND zone on the bottom layer.
I've not had chance to figure out why this is happening, and I think perhaps all the via's to GND may need to be replaced.

So far I've made one change to the schematic, as it looks like the USB D+ was missing the 1.5k pullup to 3.3V that is required by the USB Spec and important if the board has to re-enumerate the USB.

Although the PCB looks good, its wide than the Blue Pill which is a problem on breadboards as there is only 1 row of pins available on each side.

Which makes me wonder if it would be possible to rotate the F405 by 45 deg and perhaps use a 4 layer board for routing - as it would be impossible to route on a 2 layer. However I'm not sure if this would help or worth the additional cost.

The other thing which seems to be making the board wider is are the decoupling caps, and the power LED and its series resistor.
I think that if the LED and resistor are moved, and all the tracks re-routed, the width could be reduced a bit e.g. probably by 0.1 inch at least

If a power LED is needed at all, I'm sure it can be positioned elsewhere


One other omission, seems to be the 32khz crystal. I think there is space on the board for this, and I presume as its low frequency, that the tracks to the crystal don't need to be ultra short.
F405Pill.pdf
(84.56 KiB) Downloaded 17 times
Print F405Pill-brd.pdf
(77.01 KiB) Downloaded 12 times
Print-F405Pill-brd.png
Print-F405Pill-brd.png (135.85 KiB) Viewed 931 times

racemaniac
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Re: F405 & F411 versions of the BluePill

Post by racemaniac » Fri Sep 29, 2017 6:15 am

As i've mentioned before, i've done plenty of modifications on bluepill boards :).
Started out with putting a f303 on it (which is fairly easy to do)

But i've also got a bluepill with an F411 on it, and there are also compatible F401, F410, F412 & F413 for it (especially the F413 is ridiculous. 1.5Mb flash, 320kb RAM, and tons of peripherals (but of course you're still limited to the 36 IO pins...)

the soldering is a PITA, as these are QFN chips, but if you've got a hot air station, it's doable.
And the only other thing you need to do, is put a capacitor on pin 22 (PB11), as on the 4 series it's an extra capacitor for the internal voltage regulator, and not PB11 (which isn't present..)

see thread here: viewtopic.php?f=39&t=1658

little extra not (initially?) mentioned in that thread: the bluepill is the only good board to do this on. The maple mini's pads don't fit the QFN chips, andn the blackpill is REALLY annoying since it has smd caps right next to the stm32, so changing the stm32 also means you'll be removing the caps, and then have to get them back on >_<.
bluepill411.jpg
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RogerClark
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Re: F405 & F411 versions of the BluePill

Post by RogerClark » Fri Sep 29, 2017 6:47 am

@racemaniac

Thanks

I think perhaps the 41x on the BluePill form factor would be better than the F405 on the larger form factor, as there are plenty of larger F4 boards around.

I just looked on AliExpress, and the F411 is available for $4, no one seems to sell the F413 etc

I'll have a go at entering what we have for the BluePill schematic into KiCad and post to a different repo

http://wiki.stm32duino.com/images/c/c1/ ... ematic.pdf

racemaniac
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Re: F405 & F411 versions of the BluePill

Post by racemaniac » Fri Sep 29, 2017 7:54 am

i've got 2 412's and 1 413 lying around (used them to get up to the 50€ mark for free shipping from digikey). But they're indeed not found on aliexpress/ebay/... so a lot more expensive (but also a lot more powerful).
The only sad thing on the f411 is that it only has 1 ADC (so not all pins can do ADC), and no DAC. but it does have i2s (so you can connect a 24 bit I2S dac on it), and a 4 bit SDIO port :). Which both are awesome in bluepill format. One small issue is that you can't both have the 4 bit sdio & an i2s masterclock. (on my board i'm thus using an i2s chip that doesn't require clock signal).

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zoomx
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Re: F405 & F411 versions of the BluePill

Post by zoomx » Fri Sep 29, 2017 8:00 am

Two suggestions:
1) a reset circuit Maple Mini like or better
2) Power led with solder pad that you can cut to disable for low power.

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RogerClark
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Re: F405 & F11 versions of the BluePill

Post by RogerClark » Fri Sep 29, 2017 8:12 am

@racemaniac

I was just looking at the schematic symbol in KiCad and I could not find an VDDA (analog supply for ADC I presume) but the 411 doesnt seem have that :-(

Re: ADC's
Umm. Thats not so good.

Perhaps the F405 is a better option after all, as I can't see any of the 64 pin F4's that have more than 1 ADC (but its really hard to see from STM's product selector as it doesnt list the actual number of ADC's in the selector table)

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RogerClark
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Re: F405 & F411 versions of the BluePill

Post by RogerClark » Fri Sep 29, 2017 8:14 am

zoomx wrote:
Fri Sep 29, 2017 8:00 am
Two suggestions:
1) a reset circuit Maple Mini like or better
2) Power led with solder pad that you can cut to disable for low power.
Reset circuit I think can be a PFET, I think thats what the Seeed Studio Maple clone uses, I'll try to find their schematis

Re: Power LED

Is it even necessary ?

Also
Boot1 is not really needed, it can be permanently pulled low.
Perhaps it can double as USB DISCONNECT

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RogerClark
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Re: F405 & F411 versions of the BluePill

Post by RogerClark » Fri Sep 29, 2017 8:29 am

Image

SIngle transistor USB reset


BTW. I think STM have a single NPN transistor reset circuit on some of their Nucleo's now.

I'll see if I can find that... Though I think a PNP may be a better

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Rick Kimball
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Re: F405 & F411 versions of the BluePill

Post by Rick Kimball » Fri Sep 29, 2017 8:30 am

These chips have builtin pullup/down resistors you control via the usb peripheral. You don't need/want external ones. Read up on the OTG FS PHY features in the reference manual.
-rick

racemaniac
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Re: F405 & F11 versions of the BluePill

Post by racemaniac » Fri Sep 29, 2017 8:42 am

RogerClark wrote:
Fri Sep 29, 2017 8:12 am
@racemaniac

I was just looking at the schematic symbol in KiCad and I could not find an VDDA (analog supply for ADC I presume) but the 411 doesnt seem have that :-(

Re: ADC's
Umm. Thats not so good.

Perhaps the F405 is a better option after all, as I can't see any of the 64 pin F4's that have more than 1 ADC (but its really hard to see from STM's product selector as it doesnt list the actual number of ADC's in the selector table)
All the chips have advantages & disadvantages ^^
I'm happy with the f411 for my projects, but it indeed depends on what you need :)

might also one day have a go at drawing out a compact board for a bigger f4 chip with more pins :).

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