Qeedji DMB 400 User Manual page 16

Video input connector (HDMI 1.4)
Jack 3.5 mm connector (GPIO1/IR)
N° Name
1 Voltage reference 3.3 V
2 GPIO1
3 Ground
Electrical features
Vin min
GPIO1 -0.5 V
The 3.3 V pin must not be used as power supply, but rather as a reference voltage.
Along the device booting, the GPIO1 is configured as input during some seconds. And then after the system startup, the GPIO1 is operational.
The GPIO has a weak pull-up.
It is not recommended to hotplug/unplug the GPIO1 connector, which could damage the device.
Principle schematics for several use cases
Three wires input configuration for GPIO1:
Two wires input configuration for GPIO1:
Output configuration for GPIO1:
Vin max VOH min
3.6 V 2.9 V
Write/Read
IN or OUT
VOL max
0.4 V
16
Control
CPU/GPIO1
VIH min VIL max
2.0 V 0.8 V