HUAWEI TECHNOLOGIES CO., LTD.
Page 25
The keypad circuit consists of KCOL0-KCOL4 and KROW0-KROW4, which form a
5*5 keypad matrix. In particular, the KCOL series contains internal pull-up. The initial
state of the KROW series is low level. When the key is pressed down, the KCOL is
pulled down. After the interrupt report to the CPU, the value of the key is confirmed
according to the signals transmitted by the KCOL.
5.2 Fault Summary
First confirm whether all keys or individual keys cannot work properly. In the case that
all keys cannot work properly, check whether one of the KCOL wires is always low.
Check whether it is due to a stain on DOME. Then change DOME to perform a cross
test. ESD damage of each wire may result in the keypad failure. In the case that
individual keys are faulty, check whether KCOL or KROW wires are the same. In that
way, check the signals of the network.
5.3 Cases
Key OK was faulty. The corresponding KCOL and KROW were normal. Use ethanol to
cleanse the corresponding DOME chip.
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