Goal: creating a visual summary of GPIO configuration modes. The summary at the bottom shows the major configuration choices.

 

Basic electrical info: GPIOs can sink or source up to ±8 mA, and sink or source up to ±20 mA (with a relaxed VOL/VOH)

except PC13, PC14 and PC15 which can sink or source up to ±3mA.

When using the PC13 to PC15 GPIOs in output mode, the speed should not exceed 2 MHz with a maximum load of 30 pF.

For more I/O static and AC characteristics refer to the product spec pdf page 109.