Tool/software:
We need your support to debug on the display blank failure reported. Backlight driver used in the display – LP8860Q1.
Display interface with the backlight driver is as below
Problem statement: Display blank.
Issue analysis:
- We observed only no backlight but the display content is available still. This is confirmed by visual when we flash light over the TFT.
- Battery voltage is 14V.
- I2C communication to backlight driver and TFT is available
- Register dump is taken in backlight driver. Slave – 0x2D. We have taken register dump in working and non working displays and comparison attached.
- Observations from the dump
i) No fault flags in TFT as well as backlight driver. Refer 0x0E, 0x0F, 0x10 address.
ii) PWM registers 0x17, 0x18 – 0.
iii) TEMP registers 0x13, 0x14 are 0.
iv) LED current registers 0x15,0x16 – 0.
v) Address 0x30 returns 1 in non working board and in working it returns 0xb.
vi) Address 0x70 through 0x78 returns all 0 in non working, in working driver there are values.
We are not intialising/ configuring any of the registers through I2C during our operation. Everything is default and the modes are all set HW.
In the issue board we tried to unlock EEPROM and configure PWM hardcoded based on backlight register instead of PWM pin. But even if we follow the unlock procedure we are not able to over write PWM values
We need your support to review the register values and explain the scenario in the backlight driver of issue board. Kindly provide immediate attention on this issue,
