F405 & F411 versions of the BluePill

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mrburnette
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Re: F405 & F411 versions of the BluePill

Post by mrburnette » Tue Oct 31, 2017 11:14 pm

RogerClark wrote:
Tue Oct 31, 2017 8:17 pm
]
Re: Regulator for analog Vcc

I presume that Leaflabs had a good reason for using the second regulator. I suspect, its potentially cheaper and takes less space on the PCB than the passive components you would need instead
Not sure, as the regulator will need at least 2x caps anyway (1x at the input, 1x at the output), and you still need at least a decoupling cap near STM32's AVDD pin, so it is necessarily more expensive, takes more space, and dissipates more power than a passive solution. Probably Leaflabs did not think much when doing this, and just used a bazooka to kill a fly. BTW, the Mapple is the only small dev board I have seen that used a second LDO for analog supply :)
The LeafLab Maple Mini was a 4 layer PCB with an analog ground plane and a separate digital ground plane. The separate voltage regulator for the analog likely was a decision made to enhance the overall low-noise floor. Most of us have come to think of the Maple Mini being the 2-layer knockoff from China.

Ray

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RogerClark
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Re: F405 & F411 versions of the BluePill

Post by RogerClark » Wed Nov 01, 2017 12:15 am

Thanks Ray. You're right, most of us forget it was 4 layer...


@squonk42

I forgot about F103R compatibility.

I think this needs to be a secondary consideration, as the primary focus as F4

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Re: F405 & F411 versions of the BluePill

Post by RogerClark » Wed Nov 01, 2017 6:53 am

I've just noticed that the Baite Maple mini clones also have components on both sides of the PCB.

The MCU is on the underside of the board, along with 8Mhz crystal (in a SMD package) and the regulator and the USB reset transistors

The top has the buttons, LEDS, USB socket and other passive components.


So...

My guess is that the cost of putting components on both sides of the boards can't be a big factor to these companies, otherwise they'd have spent a bit more time on the design and put all the components on one side.

BTW. The original LeafLabs Maple mini has components on both sides of the board as well

(there is photo of the bottom of the Maple mini on Leaflabs site)
Image

racemaniac
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Re: F405 & F411 versions of the BluePill

Post by racemaniac » Wed Nov 01, 2017 7:35 am

RogerClark wrote:
Tue Oct 31, 2017 8:17 pm
Re: 50 mm long board and components in bottom of board

I think with too many constraints, the board is going to take months to design and may never get produced.

Perhaps move as many as possible to the top without wasting hours of time and potentially adding conflicts to the PCB
tbh, personally i still prefer the bluepill solution: big things on 1 side, small things on the other.
It's the reason why the bluepill has been the board i've been putting other mcu's on. the maple mini's pads don't allow a qfn to fit, and the blackpill has small caps right next to the mcu, so changing the mcu means you'll also be removing the caps, and is just annoying extra work :).
if we want to allow for people to change crystals/mcu/... easily, making sure there are no tiny caps/resistors right next to them makes a lot of sense :).

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Re: F405 & F411 versions of the BluePill

Post by Squonk42 » Wed Nov 01, 2017 9:52 am

Re: LeafLab Maple Mini was a 4 layer PCB with an analog ground plane and a separate digital ground plane

OK, then it is a completely different story and much more understandable, thank you Ray! Low-cost was then not the primary concern like for us here. 4-layer is more expensive.

Re: Components on both sides of the PCB
It looks like it is a cheap option, so let's go for it!

However, I agree with @racemaniac to put all large components (what about the SD Card connector?) on top and small ones on the bottom. Plus, because of the package size, we don't have much space to sprinkle the decoupling caps around it, putting them below the chip would be much better and also easier for replacing the chip. For crystals, this is may be different, as vias should be avoided if possible on the clock traces.

Re: F103R compatibility
Not only F103R, but all STM32 MCUs featuring the simple USB Device peripheral in LQFP64 package:
STM32L052R6 STM32L052R8 STM32L053R6 STM32L053R8 STM32L063R8 STM32L072RB STM32L072RZ STM32L073RB STM32L073RZ STM32L083RZ STM32L100R8 STM32L100R8-A STM32L100RB STM32L100RB-A STM32L100RC STM32L151R6 STM32L151R6-A STM32L151R8 STM32L151R8-A STM32L151RB STM32L151RB-A STM32L151RC STM32L151RC-A STM32L151RD STM32L151RE STM32L152R6 STM32L152R6-A STM32L152R8 STM32L152R8-A STM32L152RB STM32L152RB-A STM32L152RC STM32L152RC-A STM32L152RD STM32L152RE STM32L162RC STM32L162RC-A STM32L162RD STM32L162RE STM32L433RB STM32L433RC STM32L443RC STM32L452RC STM32L452RE STM32L462RE STM32F070RB STM32F072R8 STM32F072RB STM32F078RB STM32F102R4 STM32F102R6 STM32F102R8 STM32F102RB STM32F103R4 STM32F103R6 STM32F103R8 STM32F103RB STM32F103RC STM32F103RD STM32F103RE STM32F103RF STM32F103RG STM32F302R6 STM32F302R8 STM32F302RB STM32F302RC STM32F302RD STM32F302RE STM32F303R6 STM32F303R8 STM32F303RB STM32F303RC STM32F303RD STM32F303RE STM32F373R8 STM32F373RB STM32F373RC
This is a long dropped-compatibility list for just a small 0402 pull-up resistor, don't you think?

Now, I agree that the Maple Mini dual transistor disconnect feature is probably a bit of overkill.

racemaniac
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Re: F405 & F411 versions of the BluePill

Post by racemaniac » Wed Nov 01, 2017 10:30 am

Concerning the dual supply: if we don't go for a dual supply, can someone draw me a schematic of what we would replace it by?

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Squonk42
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Re: F405 & F411 versions of the BluePill

Post by Squonk42 » Wed Nov 01, 2017 10:40 am

racemaniac wrote:
Wed Nov 01, 2017 10:30 am
Concerning the dual supply: if we don't go for a dual supply, can someone draw me a schematic of what we would replace it by?
See my post above: a simple PI filter with 1µF cap, 470R ferrite bead and 100nF close to the AVDD pin:
ImageImage

I will try to experiment this filter on a real BluePill 3.3 pin tomorrow

Other subject, I found this simple (no push-push) narrow (12.2 mm) and cheap (0.17RMB = $0.03) SD Card connector on Taobao:
https://item.taobao.com/item.htm?spm=a2 ... t=4#detail
Image

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Squonk42
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Re: F405 & F411 versions of the BluePill

Post by Squonk42 » Wed Nov 01, 2017 6:29 pm

Re: PCB overhang

Do we need to keep the PCB overhang on the outside of the header rows? On one hand, it is convenient to silkscreen to pin name, but OTOH, it makes the board wider by 2 pins on a breadboard...

Re: VBUS valid sensing for HNP SRP

In the STM32F4 Reference Manual RM0090, page 1254, section 34.6.2, there is a mention about connecting PA9 as a VBUS sensing for HNP/SRP: googling around, I found that both SRP (Session Request Protocol) and HNP (Host Negotiation Protocol) are 2 USB OTG protocols, but does anybody knows if these are required for proper USB operation or not?

Having to connect PA9 to VBUS would be rather inconvenient, as it also has the USART1_TX function used by the ROM bootloader...

racemaniac
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Re: F405 & F411 versions of the BluePill

Post by racemaniac » Wed Nov 01, 2017 6:40 pm

what i also like about the overhang is an easy place to route the 5v around the entire board, and it's easy having these edges where the fill zones can easily go to, when designing the board it made getting the planes get everywhere on the board a lot easier.
i was also doubting keeping them, but both for the labels and ease of routing, they do have their advantages.

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RogerClark
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Re: F405 & F411 versions of the BluePill

Post by RogerClark » Wed Nov 01, 2017 7:58 pm

IMHO. Easily visible pin names on the silk screen is essential.

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