Pot luck board. aka STM32 Smart V2.0

I recently ordered one of these, on a whim because it was so cheap …

… and received one of these instead …

PotLuckFront.JPG (53.1 KiB) Viewed 1462 times

Sounds like a fun secret santa idea for this forum
You order a random stm32 board for your target, and they can be surprised by what arrives in their mailbox XD.

It is actually quite a good board, very compact, oled connector, mini USB rather than micro, LED, 2 x buttons (one reset) and very well constructed. The inclusion of the 24C04 is useful too. I’ll keep you posted if I ever hear back from ebay or the supplier.

If the ugly board is ugly, then this is more the cute board. All of the soldering is perfect, the silk screen and layout are tidy, and apart from the dodgy ST logo on the rear, it is fine and did I mention the soft green eyes blinking at me .

Well worth the not very much I paid for it.

Andy, you’ve placed some bad URL again, probably including your session cookie that prevent seeing them …

martinayotte wrote:Andy, you’ve placed some bad URL again, probably including your session cookie that prevent seeing them …

i ordered some of the first one with stm32f103rc(??), then found it had a stm32f107 on it, but both types had the nrf24 socket.
they still program and seem to work.
i muttered about it here and added some info on them to the wiki.
i speculated that the boards were distinguished by the button colour, nope

stephen

I finally got round to playing with this board today.
It has an OLED demo flashed to it, but unfortunately I don’t have a suitable OLED display to test it with.
I’ve attached the file for the curious. It is a .bin but I added a .txt suffix to keep phpBB happy.
A quick glance at it shows that it contains some strings..
...
0.96' OLED TEST
mcudev.taobao
2014-06-16
ASCII:
CODE:
Eeprom--OK

...


Thanks

A lot of additional info and even a schematic with full BOM added to the wiki.
Time to sleep now I think.

Thanks

More info and details of how to access the on board 24c04 eerom added to Wiki page.

Thanks Andy

I lot of boards have similar eeproms

The 24c02 is simple to write to, bur the 24c04 had me scratching my head as most of the libs out there are for larger capacity devices (24c32 and above).

After a quick read through the datasheet I discovered that you can effectively treat the two 256 byte pages of the 24c04 as two 24c02 devices on consecutive addresses.

Since most of the boards simply tie the chip address pins low, this becomes a matter of reading/writing 256 bytes to device address 50, or reading and writing 256 bytes to device address 51. I did need to add external 10k pullups too as these are not fitted on this board.

The same consecutive address trick should work for 24c08 and 24c16 devices too but I don’t have any of these to test with.

Below is the result of me writing some data to the first page (device 0x50), then some similar data to the 2nd page (device 0x51)
Scanning...

I2C device found at address 0x50
-- : 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
-
00 : FD FA 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F -
10 : 70 17 17 71 44 02 16 17 18 19 1A 1B 1C 1D 1E 1F -
20 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
30 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
40 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
50 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
60 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
70 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
80 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
90 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
A0 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
B0 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
C0 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
D0 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
E0 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
F0 : FF FF FF FF FF FF FF FF FF FF CE 1E FF FF FF FF

Done

I2C device found at address 0x51
-- : 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
-
00 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
10 : 70 17 17 71 44 02 FF FF FF FF FF FF FF FF FF FF -
20 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
30 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
40 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
50 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
60 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
70 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
80 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
90 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
A0 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
B0 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
C0 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
D0 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
E0 : FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF -
F0 : FF FF FF FF FF FF FF FF FF FF CE 1E FF FF FF FF
Done

Thanks Andy, I was wondering why these eeproms were used, but I see they have a million write cycles.

This is very handy for me, as I am building a controller for an electric bike and want to store the milage.

I will probably buy a few to use with the maple mini and blue pill etc

@Roger, don’t purchase those low 8 bits addressing EEPROMs, choose 24C32 or higher, which are 16 bits addressing, and they are not much more expensive than the others, while most of them still have 1 million write cycles.

Thanks Martin

I’ll take a look on eBay and AliExpress and see whats available

At the moment I’m going to need to use battery backed ram and also use the onboard flash to store the data, as its a project I’m doing as a Christmas gift and the eeproms won’t arrive in time for me to integrate them into the project

RogerClark wrote:need to use battery backed ram

Yes. I did consider FRAM but I’m a cheapskate and I think I can do it using internal flash, As the STM32 has thousands of erase cycles, and lots of free flash (I think I have at least 32k free).

So if I increment the write location in flash, it gives be around 32k write before I need to erase a single page, and if I can erase each page tens of thousands of times, then that gives me serveral hundred thousand write to flash.

Or I could just add a capacitor that keeps the CPU running for long enough to write to flash when the power is removed (and use the same principal of incremental addresses in flash)