Meaning off GPIO_Speed declaration

[infoinfo973]

Posted on November 04, 2010 at 09:38

Meaning off GPIO_Speed declaration

[John F.]

Posted on May 17, 2011 at 14:13

Please see RM0008 Reference manual section 8.1.

Output MODE bits MODE[1:0] Meaning 00 Reserved 01 Max. output speed 10 MHz 10 Max. output speed 2 MHz 11 Max. output speed 50 MHz Also see the Data Sheet for your device and look at the Electrical characteristics / Input/output AC characteristics. Basically, choose lower speed if you don't need fast clocks or edge transitions. It will reduce EMC problems.

[Tesla DeLorean]

Posted on May 17, 2011 at 14:13

See also SLEW RATE CONTROL

If you drive the pin aggressively to get sharp edges, and over come line capacitance, you will typically see more over-shoot/under-shoot, and ringing, in the output signal.

[dthedens2]

Posted on May 17, 2011 at 14:13

Well, he does have a point.  Table 19 shows these values for MODE.  But no where does RM0008 explain what they mean.  The STM32F103ZE (which I use) data sheet table 47 has some additional info, but not much.

WHat really happens when MODE is set to 10 and the code performs a pin high and then a pin low? For that info, one has to go to other ARM vendor documentation and hope that the ST works the same.