Huawei U8860 Maintenance Manual page 75

U8860
Maintenance Manual
The principle of capacitive touch panel is: Attaching a layer of transparent metal conductive
materials on the glass. When the finger touches the touch panel, the capacity on the touching
point varies, which causes the oscillator frequency to vary. Then system can obtain the
touching position according to the frequency variation.
As the touch panel module is integrated on the touch panel, the main board and touch panel
must be connected by a BTB connector. The connector can be damaged easily. In addition,
you must power on the touch panel according to the power-on sequence. First supply the 2.7
V power, and then supply the 1.8 V power; otherwise, the touch panel is disabled. When the
touch panel is operating, the I2C controls data transmission.
Four touching key fields are added to the U8860's 4-inch capacitive touch panel, and four
backlight LEDs for the four keys are added to the touch panel module.
The definitions of the interfaces for touch panel and MSM8255 and touch panel and PM8058
are as follow:
Signal
VREG_L10_2P7
VREG_MSM_L20_1V8 Touch panel digit power supply and I/O connector power
TOUCH_INT
I2C_SCL_HW
I2C_SDA_HW
TOUCH_RESET

Failure: The touch panel is faulty.
Solution:
Issue 1.0 (2011-11-14)
Troubleshooting process:
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd
Description
Touch panel analog power supply, 2.7 V
supply, 1.8 V
Touch panel interrupt signal
Touch panel' I2C clock cable
Touch panel' I2C data cable
Touch panel reset signal
9 Principles and Troubleshooting
70