11.6 Blue LED

Helios contains a programmable blue LED along the top edge of the board, near the VGA connector. This LED is controlled by the Vortex processor GPIO port 3 bit 4. It can be turned on and off in the BIOS and in software. The LED is on by default. To turn the LED on or off in the BIOS, go to the Chipset menu, select South Bridge Configuration, and then LED. This will select the power-on state of the LED. To control the LED via software, write to GPIO port 3 bit 4. The direction control register for GPIO port 3 is preset by the BIOS and should not be disturbed.

outp(0x7B, inp(0x7B) & 0xEF); // clear bit 4 of port 3 to turn LED ON outp(0x7B, inp(0x7B) | 0x10); // set bit 4 of port 3 to turn LED OFF