i bought the Wi-Fi / Bluetooth Starter Kit with the Aster Carrier Board. Im trying to toggle the LED4 on the Carrier Board but it won’t work. The Datasheet says that the led is connected to Pin 104.
I am wondering which exact datasheet and page thereof you are talking about. Anyway, it is indeed connected to the SODIMM edge connector pin 104. Now, you would need to look into the Colibri iMX6ULL datasheet to figure out what exact SoC ball routes to that SODIMM pin. Table 3-1 tells you that it is ENET1_RXER and the Functions List in section 4.4.1 shows you this being gpio2.IO. The following list shows you what Linux kernel GPIO number it maps to: 39.
Can someone tell me which gpio is the correct one to toggle the led?
Alternatively, you may use libsoc where that whole carrier board/module ball/pin mapping is nicely abstracted.
Keep in mind that one also needs to make sure resp. pin is muxed properly in the device tree. If you are using the Aster device tree this should already be the case as can be seen here.