I'm trying to figure out how much current is coming from the GPIO on olinuxino a20 (and a20 SOM, for that matter.) I checked the manual and couldn't find anything.
I hope you mean the maximum that can be supplied. See the datasheet as it's in there.
I don't think the total is, but expect "not much" unless you fit a good heatsink in which case go for "somewhat more".
Do not fail to use resistors (or the like) to limit the current or expect a dead pin/chip.
John
Oh, durr. Thanks John, I think I get it now. I'll take another look through and see what I can find.
You can easily add some drivers such ULN2003 or ULN2803, this will provide strong outputs which can drive things such relays.