2023-10-12 09:21 AM
so my school has an old pcb milling machine that i want to bring back to life, so the first thing i want to do with it is to make a stm32f103c6t6a board, can someone check if that schematic could work and if i can implement other capabilities in this board?
ps (the pcb milling machine is a lpkf protomat s42 that uses boardmaster and some old version of circuitcam)
2023-10-12 09:23 AM - edited 2023-10-12 09:25 AM
also i didn't quite understand how i should implement oscillator for clock, i put a 16mhz for now i may be implementing a 8mhz oscillator, do i need a 32.768K oscillator or i can operate usb in a reliable way without it?
is that implementation good?
2023-10-12 10:44 AM
The F103's typically use an 8 MHz crystal to permit 72 MHz PLL operation, and USB / CAN clocking. It can probably take a 16 MHz one, but you'd be constantly modifying example code, and HSE_VALUE settings.
The 32.768 KHz LSE is needed only if you need the RTC and STANDBY operation, as it's the only clocking source with primary power off.
2023-10-12 12:03 PM
For the rest is my schematic ok?
2023-10-12 12:56 PM
Just wondering how / why you chose PB10 and PB11 for the data lines of the USB? I might be incorrect, but looking at Page 27 of this link USBDM and USBDP are on PB11 and PB12 ... https://www.st.com/content/ccc/resource/technical/document/datasheet/0d/93/e0/d7/77/bf/4c/54/CD00210843.pdf/files/CD00210843.pdf/jcr:content/translations/en.CD00210843.pdf
Might be worth double checking that your choice is correct against the datasheet for the exact IC.
2023-10-12 03:42 PM
The R2 is not connected... But the best question is why are you choosing that old and limited MCU instead of something newer?
2023-10-13 12:32 AM
Yes, PB11 and PB12 are for USB connection. And I would also put two small resistors of approx. 10-20ohm on the USB data wires.
2023-10-13 12:33 AM
Sorry, PA11, PA12
2023-10-13 12:40 PM
Thanks for the reply, this was my first try making schematic and as I didn't had cube MX installed on my machine I couldn't look up the right pin for usb, on the newer design that I did the pin are set on PA11 and PA12, I will also implement a can bus chip on board (just for fun) a classic mcp2515 , and I will try to create some driver for a temperature sensor, but for now I'm trying to understand more about the oscillator configuration
2023-10-13 12:43 PM
I got it for a few cent from AliExpress with other chip, I thought it was a decent way to start making a board and even if I make some mistake I wouldn't waste too much money and on the other hand if it work I can buy a more recent chip ,I also have a basic stm32f103c8t6 and a stm32f103ret6, I got them on AliExpress for less than 50cent for each and they don't seem to be fake