F405 & F411 versions of the BluePill

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Pito
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Re: F405 & F411 versions of the BluePill

Post by Pito » Sat Jan 06, 2018 2:14 pm

:idea: Can you reuse the Vcc/Gnd pins from the SWD header for the battery as well :?:
a) You do not need battery connected when doing programming via SWD..
b) You may not need Vcc connected on the Vcc pin while programming..
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Squonk42
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Re: F405 & F411 versions of the BluePill

Post by Squonk42 » Tue Jan 09, 2018 10:04 pm

Pito wrote:
Sat Jan 06, 2018 2:14 pm
:idea: Can you reuse the Vcc/Gnd pins from the SWD header for the battery as well :?:
a) You do not need battery connected when doing programming via SWD..
b) You may not need Vcc connected on the Vcc pin while programming..
Yes! So, I added a 0R between the SWD +3.3V pin (now +VBAT) and the +3.3V signal, so:
  • it behaves like on the BluePill if there is no LiPo charger circuit, the +3.3V pin on the SWD header is an input that will compete with the LDO output (bad :? )
  • if you have a LiPo charger circuit and no battery connected, just connect the SWD +3.3V power to the +3.3V pin on the header near the NRST pin (still bad :? )
  • better: feed the board from +5V or USB if no battery or no battery charger circuit!
  • but if you have a LiPo charger circuit and a battery connected, just don't connect the pin to anything and use the battery power
On other subjects, I fixed the AGND problem on the analog LDO and separated the GND pads on the capacitors in the CLC filter option: actually, one is now on AGND, the other on GND and much farther apart.

I also have the Olimex LiPo charger circuit routed, I just need to clean up all this mess before committing the changes.

racemaniac
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Re: F405 & F411 versions of the BluePill

Post by racemaniac » Wed Jan 10, 2018 8:23 am

Squonk42 wrote:
Tue Jan 09, 2018 10:04 pm
Pito wrote:
Sat Jan 06, 2018 2:14 pm
:idea: Can you reuse the Vcc/Gnd pins from the SWD header for the battery as well :?:
a) You do not need battery connected when doing programming via SWD..
b) You may not need Vcc connected on the Vcc pin while programming..
Yes! So, I added a 0R between the SWD +3.3V pin (now +VBAT) and the +3.3V signal, so:
  • it behaves like on the BluePill if there is no LiPo charger circuit, the +3.3V pin on the SWD header is an input that will compete with the LDO output (bad :? )
  • if you have a LiPo charger circuit and no battery connected, just connect the SWD +3.3V power to the +3.3V pin on the header near the NRST pin (still bad :? )
  • better: feed the board from +5V or USB if no battery or no battery charger circuit!
  • but if you have a LiPo charger circuit and a battery connected, just don't connect the pin to anything and use the battery power
On other subjects, I fixed the AGND problem on the analog LDO and separated the GND pads on the capacitors in the CLC filter option: actually, one is now on AGND, the other on GND and much farther apart.

I also have the Olimex LiPo charger circuit routed, I just need to clean up all this mess before committing the changes.
sounds great :)

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Pito
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Re: F405 & F411 versions of the BluePill

Post by Pito » Wed Jan 10, 2018 9:57 am

:idea: Also - for demanding users who are ready to pay $3 more for 4 layers - what would happen if you add 2 layers - GND and VCC? It may help you with routing as well..
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Squonk42
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Re: F405 & F411 versions of the BluePill

Post by Squonk42 » Wed Jan 10, 2018 9:30 pm

Pito wrote:
Wed Jan 10, 2018 9:57 am
:idea: Also - for demanding users who are ready to pay $3 more for 4 layers - what would happen if you add 2 layers - GND and VCC? It may help you with routing as well..
Actually, routing is not that bad, there is still some unused space left :mrgreen:

The idea is to get an F4 version of the BluePill board, if possible made by a Chinese manufacturing house. IMO, a large part of the success of the BluePill board is because of its cheap price: it's in the same ball park as the Arduino Pro Mini @$1.72. You can get cheaper boards featuring ATMega 168, ATTiny85 or down to STM8S103F3P6 @$0.66, but you get so much more power with the BluePill...

OTOH, you can get much more powerful chips with a little more money, including ESP8266 and ESP32.

So if there is a sweet spot for an F4 BluePill, it must be at the lowest possible cost, with the benefit of raw CPU power and numerous peripherals with DMA.

Most people here are very concerned about price, so I think we should stick to a 2-layer design only. I admit 4 layers would bring better performance (including for EMC reasons), but then, you can always add the GND and power layers and clean up traces if required for your needs.

Ollie
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Re: F405 & F411 versions of the BluePill

Post by Ollie » Thu Jan 11, 2018 3:46 pm

I do agree

victor_pv
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Re: F405 & F411 versions of the BluePill

Post by victor_pv » Thu Jan 11, 2018 5:25 pm

I agree with leaving it at 2 layers, at least at the moment.
Let's try to get some prototypes working, then if we need to change things for another revision because there is too much noise or whatever else, can be done later.

ChrisMicro
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Re: F405 & F411 versions of the BluePill

Post by ChrisMicro » Thu Jan 11, 2018 6:49 pm

On Hackaday there was this article about a prototyping company. Probably it could be useful to get boards fast.

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Squonk42
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Re: F405 & F411 versions of the BluePill

Post by Squonk42 » Sat Jan 13, 2018 9:01 pm

I pushed a new version of the BluePill F4 board with the following features:
  • Main thing: I added a LiPo battery charger as an option on the bottom of the board below the SWD connector. It uses the same MCP73812T-420I/OT and ideal diode made up of a PMOS FET transistor and a Schottky diode as Olimex in its OLIMEXINO-32U4 board. The battery has to be connected to the 2 extreme pins on the SWD header,
    as there are other ways to power the board anyway. If the charger option is not installed, a 0R mounted on the board top side makes it strictly compatible with the original Bluepill by connecting it to +3V3
  • The GND on the analog LDO is now on AGND
  • The alternative (simpler) analog power supply using a CLC filter is now laid out better
  • The VBUS_EN pin has been changed from PC4 to PC0, as this pin is less useful for anything else
  • The pads on the bottom side of the board for PC1-PC7 are now aligned and no longer below the SDCard, with a nice 1.27 mm pitch
Here is what it looks like:
Image
Image

Please let me know if you find a problem, or just if you want to discuss regarding the board!

racemaniac
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Joined: Sat Nov 07, 2015 9:09 am

Re: F405 & F411 versions of the BluePill

Post by racemaniac » Sun Jan 14, 2018 8:43 am

Squonk42 wrote:
Sat Jan 13, 2018 9:01 pm
I pushed a new version of the BluePill F4 board with the following features:
  • Main thing: I added a LiPo battery charger as an option on the bottom of the board below the SWD connector. It uses the same MCP73812T-420I/OT and ideal diode made up of a PMOS FET transistor and a Schottky diode as Olimex in its OLIMEXINO-32U4 board. The battery has to be connected to the 2 extreme pins on the SWD header,
    as there are other ways to power the board anyway. If the charger option is not installed, a 0R mounted on the board top side makes it strictly compatible with the original Bluepill by connecting it to +3V3
  • The GND on the analog LDO is now on AGND
  • The alternative (simpler) analog power supply using a CLC filter is now laid out better
  • The VBUS_EN pin has been changed from PC4 to PC0, as this pin is less useful for anything else
  • The pads on the bottom side of the board for PC1-PC7 are now aligned and no longer below the SDCard, with a nice 1.27 mm pitch
Here is what it looks like:
Image
Image

Please let me know if you find a problem, or just if you want to discuss regarding the board!
niiiice XD
one tiny remark though: there's a silk screen line going trough the pc7 pad :) (although when plotting the gerbers, you can substract it from the silk screen :) ).

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