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R
RDR102
Associate
October 12, 2023
Question

making my own board from scratch (literally)

  • October 12, 2023
  • 4 replies
  • 3528 views

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)

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4 replies

R
RDR102Author
Associate
October 12, 2023

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?

Tesla DeLorean
Tesla DeLorean
Guru
October 12, 2023

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.

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R
RDR102Author
Associate
October 12, 2023

For the rest is my schematic ok?

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Senior II
October 12, 2023

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.

ONadr.1
ONadr.1
Senior III
October 13, 2023

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.

    ONadr.1
    ONadr.1
    Senior III
    October 13, 2023

    Sorry, PA11, PA12

      Piranha
      Piranha
      Principal III
      October 12, 2023

      The R2 is not connected... But the best question is why are you choosing that old and limited MCU instead of something newer?

      R
      RDR102Author
      Associate
      October 13, 2023

      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 

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