Red Pill or Blue Pill?

Generic boards that are not Maple or Maple mini clones, and don't contain the additional USB reset hardware
denis
Posts: 17
Joined: Wed May 11, 2016 8:38 pm

Re: Red Pill or Blue Pill?

Post by denis » Mon Aug 29, 2016 8:09 pm

arhi wrote:how many variants of these boards are there?!
https://youtu.be/eAvqU8QzRwU
I have found 3 variants of blue pill: viewtopic.php?f=28&t=117&p=14095#p14095

marekic
Posts: 8
Joined: Sun Sep 25, 2016 5:29 pm

Re: Red Pill or Blue Pill?

Post by marekic » Tue Sep 27, 2016 1:27 pm

New version spotted (I suppose, I'm new on this platform). It doesn't have any components on the bottom side, has screw mounting holes, and none of the headers are soldered. I don't know what chip is between oscillator and USB port - an LDO? I don't see RTC, unless it's packed under the oscillator. Shame it has weak USB port.

Image

stevestrong
Posts: 1747
Joined: Mon Oct 19, 2015 12:06 am
Location: Munich, Germany

Re: Red Pill or Blue Pill?

Post by stevestrong » Tue Sep 27, 2016 2:06 pm

Mounting holes with same size => it has less power pins than the "standard" pills...

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zoomx
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Location: Mt.Etna, Italy

Re: Red Pill or Blue Pill?

Post by zoomx » Tue Sep 27, 2016 2:31 pm

€ 1,45 !!

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Pito
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Re: Red Pill or Blue Pill?

Post by Pito » Tue Sep 27, 2016 2:41 pm

That is the voltage reg between the usb conn and the big crystal. 32kHz resonator is the yellow piece between the big crystal and the mcu. Most probably :)
It has got an 1k5 (the resistor close to B8) as the usb d+ pullup.
There is none 5V available on the headers..
BlackPill
Pukao Hats Cleaning Services Ltd.

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RogerClark
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Re: Red Pill or Blue Pill?

Post by RogerClark » Tue Sep 27, 2016 8:50 pm

Looks interesting.

I think I better order a few for testing.

marekic
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Joined: Sun Sep 25, 2016 5:29 pm

Re: Red Pill or Blue Pill?

Post by marekic » Wed Sep 28, 2016 1:39 am

stevestrong wrote:Mounting holes with same size => it has less power pins than the "standard" pills...
Yes. Although, I don't need them. But, what is also missing is 3V battery connector so that makes onboard RTC useless.
Pito wrote:That is the voltage reg between the usb conn and the big crystal. 32kHz resonator is the yellow piece between the big crystal and the mcu. Most probably :)
I believe you are right.
Pito wrote:BlackPill
:D
RogerClark wrote:Looks interesting.

I think I better order a few for testing.
I ordered four of them, and now I realize I could have ordered regular ones with 3V battery connector, since I need RTC for my current project. But OK, I intended using RTC module anyway since I wasn't aware of internal RTC of stm32f103.

madias
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Joined: Mon Apr 27, 2015 11:26 am
Location: Vienna, Austria

Re: Red Pill or Blue Pill?

Post by madias » Wed Sep 28, 2016 12:33 pm

Meanwhile the "regular" blue pill price is about 1.38 EUR (less than AVR pro mini!)
https://www.aliexpress.com/item/Free-Sh ... 44057.html
and 1.63 EUR if you buy 10pcs (registered mail - strongly recommended on ali!) : https://www.aliexpress.com/item/10pcs-l ... 93738.html

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ahull
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Re: Red Pill or Blue Pill?

Post by ahull » Wed Sep 28, 2016 1:48 pm

marekic wrote:
stevestrong wrote:Mounting holes with same size => it has less power pins than the "standard" pills...
Yes. Although, I don't need them. But, what is also missing is 3V battery connector so that makes onboard RTC useless.
Pito wrote:That is the voltage reg between the usb conn and the big crystal. 32kHz resonator is the yellow piece between the big crystal and the mcu. Most probably :)
I believe you are right.
Pito wrote:BlackPill
:D
RogerClark wrote:Looks interesting.

I think I better order a few for testing.
I ordered four of them, and now I realize I could have ordered regular ones with 3V battery connector, since I need RTC for my current project. But OK, I intended using RTC module anyway since I wasn't aware of internal RTC of stm32f103.
You can of course get the STM core to shutdown completely before you reach the lower limit of the RTC retention voltage, and run the whole thing on one battery rather than having a separate supply for the RTC. So for example, if the RTC and/or CMOS data retention registers are required you could set the project/STM to enter its lowest power mode when VCC hits say 0.3V above the LiPo protection cutoff voltage assuming you are running on a LiPo. This would be about as low as I would risk letting the supply go anyway, as allowing the protection to cut in when the processor is running risks uncontrolled behaviour rather than a clean shut down.

According to the datasheet the VBAT pin can be connected to the external battery (1.8 V < VBAT < 3.6 V), so it will continue to function so long as your LiPo Isn't allowed to drop <1.8V (at which point most LiPo cells will be toast anyway). Obviously if you are using a protected LiPo and you allow the voltage to drop below the protection threshold voltage, you loose the RTC, as the battery protection IC will disconnect the load (the STM and any other peripherals) completely from the circuit.

Monitoring the LiPo voltage might require a dedicated analog GPIO pin and a suitable voltage divider, since you need to measure that voltage *before* any voltage regulator on your board.

You will see this method used in quite a few types of consumer equipment. My Samsung phone for example powers on from battery disconnect with the date unset, so it clearly doesn't retain the RTC time without the main battery, setting the time instead from phone network time or manually, following complete power loss. It does retain the time, so long as the battery is attached, even if the battery is too flat to actually power the phone.

Clearly this may not be perfect for all scenarios, but if correctly implemented, it will be fine for most.
- Andy Hull -

Sylvan_YZY
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Joined: Mon Sep 19, 2016 8:35 am

Re: Red Pill or Blue Pill?

Post by Sylvan_YZY » Thu Sep 29, 2016 8:42 am

i have a bunch of these boards some of them even GD32 and would say i defenitely dont like the red one, for the usb is loose soldered and consumes 1 of my pull up resisters, choose the blue one

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