Hytera MD78X Service Manual page 19

Front Panel Section
Programmable Key
Up/Down Key
OK/Menu Key
Back Key
Power On/Off Key
Dial-back/End/Home
Key
Answer/Redial/Call Key
LCD Display
The TFT LCD transfers data via the bus EMIFS of U302. The control signals contain write/read enable,
memory chip select, LCD chip select and reset signal, each of which is pulled up by R36, R35, R34,
R33 and R6 respectively. The 5V voltage is converted to 3.3V by U5, in order to supply the LCD
module.
LED and Backlight
The LED enable signal is fed to the serial-to-parallel converter IC, and then is output by U302. RX
status is indicated by green LED, and TX status by red LED. Backlight is activated upon any key press.
The LEDs (red and green) in series are supplied by a 5V voltage (U902) and controlled by Q2 and Q3.
The backlight is also supplied by a 5V voltage and controlled by Q1. Control signals are output via U1.
MMC
For details, please refer to Interface Definition.
Audio output
The front panel provides two audio outputs: Handset_audio and SPK±. Handset_audio is the output of
received audio via MMC, and SPK± is the output by the audio PA (U201) as audio signal for the front
panel speaker.
Volume Control
The volume control is facilitated by the encoder switch (U7), which generates signals to be fed to U302
by GPIO17 and GPIO18.
Key
S2, S3, S7, S8, S9, S10
and S12
S5 and S11
S4
S6
S1
Screen
/
/
Conventional Mode
6
Service Manual
Trunking Mode
S3, S7, S9, S10 and
S12
S2
S8