Another STM32F103C8 board spotted on Aliexpress – Without USB

Just a note for anyone who has seen this board that I came across on Deal Extreme and AliExpress

sku_380789_1.jpg (85.84 KiB) Viewed 1013 times

Please read (again) what Roger wrote

So you will be very disappointed if you buy this board an try to use it with the bootloader or Serial USB etc – as it won’t work.

This looks like a nice board.

For me, the big disappointment is that they missed to use a standard order in the female SWD connector. If they have done it with

• 3V3
• SWCLK
• GND
• SWDIO

then you could insert a ST-Link device directly to this board without an adapter cable.

I think another downside with this board is that there are 2 rows of pins on each side.

This means you can’t stick it into a breadboard, like you can with the Maple Mini or the Blue Pill etc.

@Ollie

I’m not sure there is a standard for for SWD is there ?

My STLink dongle pinout is

VDD
GND
SWCLK
SWDIO
RESET

Roger,

I have 3 low cost dongles and all of them are sharing these 4 pins in the same order. In one case there are two rows of 4 pins and the VCC is selected by 3V3/5V jumper. Even in that case RST is on top of SWDIO. In the other case, there are two rows of 5 pins and the 5V is the 5th pin and not used with F103.

For most use cases, this board is not an alternative for Blue Pill or Baite. When breadboard mounting is not required, then the double row male connection pins is suitable for custom shields or ribbon cable quick connect.

Cheers, Ollie

I looked at it the other day it came up on Ali Express when I searched for maple mini (together with some bonsai trees). I did not bother to look at the circuit so did not realise the usb was just for power. I agree with Roger its hopeless for bread boarding but may be handy if you want a to use it as a small sub on a bigger project. If you don’t want / cant solder the f103 directly it will make a shorter break out board for the f103. The problem with buying qpf48 adapter boards is you still need someone to solder the part to the board.

Simon

I agree, there may be some projects where a shorter board is needed, but the HY-Tiny STM32F103T board would also be a contender, as its shorter than the blue pill and the maple mini and has USB.
But the HY-Tiny also has less pins, because the F103T has less pins.

I dont think building onto one of those adaptor boards is significantly smaller, but it would definitely work out more expensive than a Blue Pill.

Whoever makes the Blue Pill, must be able to source there STM32F103C8, for significantly less than the prices quoted on AliExpress for the MCU, as I cant find one listed ( even in large quantities) for under $1.40; and you can buy the Blue Pill for just over $2

The idea of building an STM32F103C8 board and *not* wiring up the USB port data pins does seem even more bizarre than wiring up the RTC supply pin directly to VCC (per the ugly board). This same bizarre design choice also seems to be a “feature” of this board too, so be aware that you would need to find and cut the trace between VBAT and VCC if you wanted to add a backup RTC battery to this board too. Someone needs to get hold of the designers of these boards and point out the error of their ways.

I did try blowing up the photos on the DX page, and messing with the colour curves in Gimp, and there appear to be two traces that head up in the general direction of the micro USB connector, (towards the edge of the board just above the 3.3V LDO) which look to be too fine for power traces, so there is a possibility that the schematic is leading us astray, and the USB data pins may be connected, all be it, potentially without the correct resistors etc.

I guess there is only one way to find out… any volunteers?

EDIT: I did find this however which also suggests the USB is power only…

https://github.com/jdesbonnet/STM32F103C8-dx-sku-380789

…which states…

“USB mini connector for power. The USB data lines are not connected (although they are brought out to test pads on the underside of the board, so it should be possible to use some wire to link to the MCU’s USB data pins). “

Thanks Andy

It does seem insane not to add the 3 SMD resistors needed to have working USB on this board, the additional cost would be just a few cents, and if they were that concerned about cost, they could have dropped the SWD header as it would duplicate connections to the GPIO pins.

I will post an issue to that GitHub repo asking them to confirm, and also letting them know that it probably works with libmaple abeit without USB

If the form factor is not the attraction, you could spend an extra £0.04 and pick up one of these instead….

http://www.dx.com/p/stm32f103c8t6-stm32 … lue-337043

.. you get more bang for the same bucks. I know which of the two I would go for.

EDIT: I see these… http://www.dx.com/p/stm32f103rct6-devel … ard-390431 … have reappeared too.

ahull wrote:If the form factor is not the attraction, you could spend an extra £0.04 and pick up one of these instead….

simonf wrote:ahull wrote:If the form factor is not the attraction, you could spend an extra £0.04 and pick up one of these instead….

Yes.
Its cheaper on AliExpress ($3.80 USD)

I was keeping an eye on the UK exchange rate, on ex.com

http://www.xe.com/currencycharts/?from= … SD&view=1W

and it looks like things are going to get a lot more expensive in the UK in the short to medium term.

(Note, This isnt so good for me, as I have some pensions tied up in the UK as well as some cash)

Yes

Brexit has cost Me £10K so far and I don’t know how much on my pension yet. The only plus is that Gold is priced in $ so that will have gone up in £’s.
They threatened that every one in the uk could be up to £4K worse off because of BREXIT I didn’t realise they meant in the first 30 minutes.

simonf wrote:Yes

Brexit has cost Me £10K so far and I don’t know how much on my pension yet. The only plus is that Gold is priced in $ so that will have gone up in £’s.
They threatened that every one in the uk could be up to £4K worse off because of BREXIT I didn’t realise they meant in the first 30 minutes.