GPIO Control

[henryay1]

Hello,

I'm trying to control the GPIOs on the JLink but noticed that JLINK_EMU_GPIO_SetState has been obsoleted in the SDK which makes jlink.gpio_set()'s implementation obsolete as well. As a workaround, I'm trying to use the JLINK_IFUNC_PIN_OVERRIDE function as mentioned in the SDK user guide. They provide an example in the guide and I tried implementing the example in Python using ctypes, but I cannot figure out how to successfully implement this in Python. I do not see any code in Pylink that uses these JLINK_IFUNC functions, so, I'm a little stuck. Can someone suggest a way to implement this or point me in the right direction?

Thanks, Henry

CC: @charlesnicholson

[charlesnicholson]

@hkpeprah @sstallion any insights here? Henry's working with us; if you could give us any pointers we'd appreciate it!

[hkpeprah]

Sorry, meant to reply to this over the weekend. Unfortunately, I've never used that API. I'll take a look later to see. What issue are you running into?

[henryay1]

I'm a newbie to working with ctypes for more advanced uses in Python, so, I'm just having trouble figuring out the best way of translating the example given in the C example in the user guide to Python. There aren't too many examples on the web on casting a function prototype to a pointer (I think that's what the example is). I tried a few methods of implementing it, but I keep getting segfaults or implementation errors.

[hkpeprah]

There's an example of binding a callback here: https://github.com/square/pylink/blob/master/pylink/jlink.py#L415

Note that we have to create a ctype function to indicate what the function is: LOG_PROTOTYPE = ctypes.CFUNCTYPE(None, ctypes.c_char_p); this basically specifies the return type, and any number of arguments that the function takes. In this instance, callback will be called with a string (string pointer), and does not return anything (is void).

More information about CFUNCTYPEs can be found here: https://docs.python.org/2/library/ctypes.html#callback-functions

[willyteske]

Hello,

I am interested in using the PIN Override functionality as well. I was able to use the JLINK_FUNC_PIN_OVERRIDE function that is exposed via JLINK_GetpFunc(...).

See jlink_ifunc_pin_override.py.txt

Shell I create a pull request based on this POC?

[hkpeprah]

Feel free to create a PR; submissions are always welcome.