5811 Datasheet, PDF (6/11 Pages) Allegro MicroSystems – BiMOS II 12-BIT SERIAL-INPUT, LATCHED SOURCE DRIVERS

JP14 – Touch Screen 1
This 4-way FPC connector is compatible with the touch screen fitted to the Hitachi SP14Q002.
JP14
1234
X+ Y+ X- Y-
JP13 – Touch Screen 2
The same touch screen inputs are also provided on this 4 pin header.
JP13
1234
X+ X- Y+ Y-
Configuration
MAKE lcdpower Digital(22)
lcdpower.On
The above two lines are needed to turn the power on to the DC-DC converter which provides VEE. The
required timing of this relative to initializing the display controller depends on the display hardware
manufacturer - in some cases this may need to be done after creating the display object.
MAKE display GLCD (3,320,240, $e0)
The value of the last parameter selects the correct module when addressing the GLCD on the application
board.
MAKE t Touchscreen(0, 1, 144)
The second parameter selects I²C bus 1.
Display Supply and Contrast Voltage Adjustment
QVGA displays require a negative voltage supply. The voltage range required varies with the make of display,
and the exact optimum voltage may vary from one unit to another as well as with temperature. Depending on
the display specification the voltage may be referenced to ground or to the +5 volt rail. Additionally a contrast
adjustment voltage is needed. Sometimes this is achieved by varying the supply voltage itself, otherwise by a
separate control voltage supplied though another pin on the connector. The application board can provide a
negative rail VEE of 0 to -24 volts referenced to either ground or the +5V rail, adjustable and with a low source
impedance from an emitter follower buffer. A contrast adjustment voltage derived from VEE via a 10k pot R7 is
also available.
R8 controls the VEE voltage. Set this before adjusting R7.
LK1: link pins 1-2 for VEE referenced to VCC; link 2-3 for VEE referenced to GND.
R7 sets the contrast adjustment voltage VADJ. Set VEE with R8 before adjusting R7.
To avoid damage do not connect the display initially and follow this sequence:
1. Set VEE and the link LK1 for the correct voltage.
2. Power off.
3. Connect the display.
4. Power on.
5. Re-adjust VEE (R8) as it may have dropped slightly because of the current drain of the display.
6. If the display uses VADJ, adjust R7 for best contrast.
Doc 44306 V20041130
VM-1 Application Board 3 (Issue A)
Page 6 of 11