Asus x450ep rev 2.0 touchpad synaptics not detect

[mon2]

Re: Asus x450ep rev 2.0 touchpad synaptics not detect

The touchpad is detached
TP CLK = 0v

This is of concern.

On the I2C / SMBUS interface, there will be a 'bus master'. The bus master is the EC controller so it will be the one to generate the CLOCK stream to communicate with the target I2C device = touchpad.

I2C / SMBUS are open-drain pins where there will be a logic low but no logic high (not push-pull style). For this reason, when the EC spits out a '1' state, the pin is floating. For the same reason, it is a MUST to have a local pull-up resistor to define the 'soft high' logic level. If the resistor is missing, then the pin will never offer a '1' state and will remain at '0'.

You have no voltage here. This may be due to a damaged pin on the EC or someone is loading down this line or the local required pull-up resistor is not working.

From the boardview, it appears that RN5202 is the pull-up resistor network for the touchpad interface.

Specifically, pin # 7 is the CLK pin from the EC and believe that pin #8 will be other side of this local pull-up resistor.

See attached.

Meter in DC volts mode - check the voltage again on pin # 7 but without the touchpad connected. You should see ~3v if all is well.

Check the voltage of pin # 8 on RN5202 which should be ~3v3.

Is this voltage present ?

Next, remove all power and configure the meter to resistance mode (10k or higher scale).

Check the resistance between pin # 7 & pin # 8 of RN5202.

What is the resistance reading ?

[Yosua]

Re: Asus x450ep rev 2.0 touchpad synaptics not detect

This is of concern.

On the I2C / SMBUS interface, there will be a 'bus master'. The bus master is the EC controller so it will be the one to generate the CLOCK stream to communicate with the target I2C device = touchpad.

I2C / SMBUS are open-drain pins where there will be a logic low but no logic high (not push-pull style). For this reason, when the EC spits out a '1' state, the pin is floating. For the same reason, it is a MUST to have a local pull-up resistor to define the 'soft high' logic level. If the resistor is missing, then the pin will never offer a '1' state and will remain at '0'.

You have no voltage here. This may be due to a damaged pin on the EC or someone is loading down this line or the local required pull-up resistor is not working.

From the boardview, it appears that RN5202 is the pull-up resistor network for the touchpad interface.

Specifically, pin # 7 is the CLK pin from the EC and believe that pin #8 will be other side of this local pull-up resistor.

See attached.

Meter in DC volts mode - check the voltage again on pin # 7 but without the touchpad connected. You should see ~3v if all is well.

Check the voltage of pin # 8 on RN5202 which should be ~3v3.

Is this voltage present ?

Next, remove all power and configure the meter to resistance mode (10k or higher scale).

Check the resistance between pin # 7 & pin # 8 of RN5202.

What is the resistance reading ?

for voltage rn5202 without touchpad

pin#7=0.02v
pin#8=3.3v

resistance for rn5202 on pin#7 & #8=4.60k ohm


does this mean the EC is broken sir?

[mon2]

Re: Asus x450ep rev 2.0 touchpad synaptics not detect

I don't have experience with ec devices so wait on other comments but it may be the case.

Some ec devices are programmable so maybe you need to reflash the controller.

One perhaps final check, with no power, what is the resistance to ground of this same ec pin ?

Also, configure the meter to diode mode. Then red meter lead (yes red) to ground. Black meter lead to the same ec pin.

What is the diode mode reading of this I2C line ?

The above details will help to determine if the pin is damaged.

Is the same touchpad still functioning on another logic board?

[Yosua]

Re: Asus x450ep rev 2.0 touchpad synaptics not detect

I don't have experience with ec devices so wait on other comments but it may be the case.

Some ec devices are programmable so maybe you need to reflash the controller.

One perhaps final check, with no power, what is the resistance to ground of this same ec pin ?

Also, configure the meter to diode mode. Then red meter lead (yes red) to ground. Black meter lead to the same ec pin.

What is the diode mode reading of this I2C line ?

The above details will help to determine if the pin is damaged.


Is the same touchpad still functioning on another logic board?

for this mobo using EC IT8572E and this ec does not need to be programmed.

and the ohm value in the measurement is 735 ohms for pin #7 on this rn5202.


thank you sir, I hope there are colleagues who have experience with this problem can help

[mon2]

Re: Asus x450ep rev 2.0 touchpad synaptics not detect

735 ohms to ground is very low.

Is this the same resistance with or without the touchpad?

The fault appears to be the EC controller.