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Dan in WY
Associate III
June 1, 2019
Question

SWDIO & SWCLK on DiscoveryVL card - can I use these as GPIO?

  • June 1, 2019
  • 3 replies
  • 1422 views

I have a DiscoveryVL card (STM32F100RB) and I want to use pins A13 & A14. The manual says I have to unsolder some jumpers on the back to use these as GPIO but then SWD won't be available. I have been using the ST-LINK utility program via a USB cable to program it. Will I still be able to program it if SWD is disabled?

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3 replies

Dan in WY
Dan in WYAuthor
Associate III
June 1, 2019

And I'm assuming pins PD0 & PD1 - are the outputs for X2 and PD14 & PD15 are the outputs for the X2 & X3. There are jumpers I have to unsolder on the back to use these pins as GPIO. Right?

Tesla DeLorean
Guru
June 1, 2019

Will make programming much more difficult. If you reconnect the pins you might need to hold the device in reset to stop your code running, or use the BOOT0 jumper.

You could also use the ROM based System Loader, and USART1 via PA9/PA10.

At the software level you'd want to Remap the JTAG/SWD off the PA13/PA14, etc pins

The VL card is very old, surely you can find better boards with more available pins if you need them.

Review the schematic to understand connectivity options. Should be one in the User Manual

https://www.st.com/content/ccc/resource/technical/document/user_manual/f3/16/fb/63/d6/3d/45/aa/CD00267113.pdf/files/CD00267113.pdf/jcr:content/translations/en.CD00267113.pdf

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Dan in WY
Dan in WYAuthor
Associate III
June 1, 2019

I will look into the F407 Discovery card. I still have a few pins left. I think I can also change the jumpers underneath and use PD0, PD1, PA13 & PA14 as they are just X2 and X3 clock outputs, which I don't need to see the clock outputs.

Tesla DeLorean
Guru
June 1, 2019

PD14/PD15??

PC14/PC15 would use the OSC32, but are low current pins powered from the backup domain. Good for inputs, not for LEDs

PD0/PD1 you'd need to remove the components, and make the bridges

Max speed from HSI clock source would be 64 MHz via PLL and HSI/2 input

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