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If the technical information states that the maximum current is 16mA at 5V you should keep the current value in the safety range. I checked the schematic for the Galileo Gen2 and I found that the IO2 is attached to the SN74LV125A buffer. Looking at its datasheet I found that the maximum current is 16mA at 5V and 8mA at 3.3V (source and sink) so according to that, the maximum current each pin can provide is 16mA at 5V.
You can check the datasheet of the SN74LV125A here: http://www.ti.com/lit/ds/symlink/sn74lv125a.pdf, in page 5.
thanks! I saw the PDF show that each pin can provide 16mA at 5V.
The following two photo is a quick test I did.
I want to read the current value from D2 so one side that I connceted to 150ohm, 300ohm and GEN, the other side I connected to the D2 (Digital 2) .
The current values were 24.8mA and 14.2mA.
Anything wrong when I did this experiment?
The tests that you are doing are correct; however you are forcing the board to manage current values out of the recommended range.
According to the datasheet, the absolute maximum current is +-35mA but the recommended range is +-16mA (check pages 4 and 5, http://www.ti.com/lit/ds/symlink/sn74lv125a.pdf). This is the safety range and you have to keep your current output in this range, otherwise the board would be under stress conditions and it may cause permanent damage.
You will read higher current values if you use lower resistance values, but you are attempting to force the board to source or sink higher current values than it has been designed for. Ideally you will get an infinite value of current but in the reality you will get a damaged device if you force it beyond its limits.