acer vn7-791g - 14203-1m - wistron - touchpad dead

[rediii]

hello guys,

i have an acer vn7-791G machine here. the touchpad died (controller shorted out - synaptics). i ordered a new touchpad, which should work fine though. but the problem is, that this clickpad is working neither. i measured the voltages on the connector tp1 and found out that the ec_tpclk signal is missing (no 3.3 V here). i replaced the kbc but no luck... resistors are working fine. tp_in_r goes low when tp is connected an stays high if no touchpad is present. already tried different flex cable (but orignal one is working fine).

3D3V_TP_S3: 3.3 v
EC_TPDATA_R: 3.3 V
EC_TPCLOCK_R: 0 V
I2C lines are present with 3.3v
tp_lid_close_: 3.3 v (when machine is running)

measurements around the connector an i2c circuit for usb serial connection are not suspicious.

i also cleared me with the newest firmware band tried different bios files...

in windows the device manager isn't recognizing the touchpad at all...

everything else looks fine, functional and without any problems. any suggestions here? thanks guys!

tp circuit on page 62, kbc lines can be found on page 24

[mon2]

Re: acer vn7-791g - 14203-1m - wistron - touchpad dead

To help with reviews, use the EXACT labels as shown in the schematic.

EC_TPCLOCK_R

is not present in the schematic.

EC_TPCLK_R

works.

1) Remove the touchpad and check the I2C lines again - any difference on the EC_TPCLK_R voltage status ?

What is the voltage of EC_TPCLK ?

2) Keep the touchpad removed -> (with all power removed) -> what is the resistance to ground of:

EC_TPCLK_R

3) Confirm that the I2C pull-up resistor for the EC_TPCLK is present @ RN6201. Also, with power removed, confirm the resistance of RN6201 resistor network, specifically the pull-up leg (pins 2 & 3) for the I2C clock line.

Personally do not have experience with the KBC but does it need to be programmed to function as needed ? Most of an internal 8051 that need firmware to function properly.

[rediii]

Re: acer vn7-791g - 14203-1m - wistron - touchpad dead

To help with reviews, use the EXACT labels as shown in the schematic.


is not present in the schematic.

EC_TPCLK_R

works.

1) Remove the touchpad and check the I2C lines again - any difference on the EC_TPCLK_R voltage status ?

What is the voltage of EC_TPCLK ?

2) Keep the touchpad removed -> (with all power removed) -> what is the resistance to ground of:

EC_TPCLK_R

3) Confirm that the I2C pull-up resistor for the EC_TPCLK is present @ RN6201. Also, with power removed, confirm the resistance of RN6201 resistor network, specifically the pull-up leg (pins 2 & 3) for the I2C clock line.

Personally do not have experience with the KBC but does it need to be programmed to function as needed ? Most of an internal 8051 that need firmware to function properly.

sry for missspelling and thank you.

there is no difference in the i2c lines, no matter if tp is present or not.

resistors are present and have the right values

resistance to ground for ec_tpclk_r is 0.L without tp, if the touchpad is connected it's first rising to over 1 Mohms, falling down to 230k slowy (same for ec_tpdata_r)

voltage for ec_tpclock is low mV

voltages for rn6201 are
pin 1 and 2: 3.3v
pin 3: low mv
pin 4: 3.3 v

kbc is not programmed

all signals for the complete circuitry are present (no shorts etc.), but ps/2 clock signal from kbc won't go high.

[mon2]

Re: acer vn7-791g - 14203-1m - wistron - touchpad dead

Remove all power. Meter in DIODE mode.

Red meter lead to ground.

BLACK meter lead to rn6201, pin # 3 - what is the reading ?

BLACK meter lead to rn6201, pin # 4 - what is the reading ?

Would you know if this KBC requires programming ? If yes, this could be the fault.

Soldering clean on the KBC ? All power & ground rails are present on the KBC ?

If the KBC has a metal ground belly - it has been reflowed properly for a good connection ? I recall on XMOS devices - had many OEMs claiming their devices on custom boards would not function. 9/10 times, the issue was with the improper connection of the metal belly pad for the XMOS devices.

[rediii]

Re: acer vn7-791g - 14203-1m - wistron - touchpad dead

there is no ec file available (or at least i didn't found one in different forums) and the old ec has had no firmware on it

diode readings:
pin #3: 0.610
pin #4: 0.612

i soldered so many kbcs, joints are looking good

no metal ground belly

maybe the chip is bad, but i doubt it.

thank you very much so far, i'll need some sleep and report the results later

one funny thing is: if i want to measure all_sys_pwrgd the device is shutting down (regardless of the smd component)... whatsoever

[mon2]

Re: acer vn7-791g - 14203-1m - wistron - touchpad dead

Based on the logic board name, this is officially the 'Poseidon Adventure' ? Sorry, could not hold back on that one. It is not everyday such a pun can be thrown out there.

one funny thing is: if i want to measure all_sys_pwrgd the device is shutting down (regardless of the smd component)... whatsoever

Perhaps the capacitive load of your meter lead causing this signal line to tank?

Confirm, when you are fully rested, the pull-up resistor @ R3708. Remove all power and confirm that it is ~10k.

Then with power, confirm that pin #1 (R3708) = ~3v3.

The diode readings look ok - was expecting to see a different diode value for the non-functional I2C bus pin.

[rediii]

Re: acer vn7-791g - 14203-1m - wistron - touchpad dead

Based on the logic board name, this is officially the 'Poseidon Adventure' ? Sorry, could not hold back on that one. It is not everyday such a pun can be thrown out there.




Perhaps the capacitive load of your meter lead causing this signal line to tank?

Confirm, when you are fully rested, the pull-up resistor @ R3708. Remove all power and confirm that it is ~10k.

Then with power, confirm that pin #1 (R3708) = ~3v3.

The diode readings look ok - was expecting to see a different diode value for the non-functional I2C bus pin.

hey, so the resistor measures 8.7k in line and 10k out of circuit. 3.3 v on pin#1 present.

[rediii]

Re: acer vn7-791g - 14203-1m - wistron - touchpad dead

hey, so the resistor measures 8.7k in line and 10k out of circuit. 3.3 v on pin#1 present.

soldered another kbc, same problem. so i think it maybe has something to do with the pch...

well well, if anyone has another idea i appreciate every little hint or help

[mon2]

Re: acer vn7-791g - 14203-1m - wistron - touchpad dead

What are the full markings on the KBC ?

From the review yesterday, the I2C bus master is the KBC for the trackpad so would think the fault is linked to the KBC.

Are datasheets available for the KBC ? Suspecting (only a guess) that firmware is required to apply a fresh KBC onboard to allow for the I2C bus master to operate normally (in open drain mode).

Respectively, do you see any I2C bus activity on this non-working interface pin during power up on a scope ?

[rediii]

Re: acer vn7-791g - 14203-1m - wistron - touchpad dead

What are the full markings on the KBC ?

From the review yesterday, the I2C bus master is the KBC for the trackpad so would think the fault is linked to the KBC.

Are datasheets available for the KBC ? Suspecting (only a guess) that firmware is required to apply a fresh KBC onboard to allow for the I2C bus master to operate normally (in open drain mode).

Respectively, do you see any I2C bus activity on this non-working interface pin during power up on a scope ?

hey, i thought i2c bus is coming from the serial bus chip cy7c65211 to the clickpad and this serial bus controller will be fed by the pch via usb 2.0 interface? kbc is communicating with the touchpad via ps/2 lanes? i'll test with scope later this evening here in germany. i'm not home atm.

there is no firmware available for the kbc and if i try to write or read with i/o programmer kbc inserted in external board, it can't read the chip id (the programmer is working fine. is use it frequently). i tried 3 different kbcs and these do not seem to be programmable at all. but maybe you are right. on the other hand the firmware should be available online somewhere, but like is said, i can't find any rom out there. will report later then! thanks again

[rediii]

Re: acer vn7-791g - 14203-1m - wistron - touchpad dead

hey, i thought i2c bus is coming from the serial bus chip cy7c65211 to the clickpad and this serial bus controller will be fed by the pch via usb 2.0 interface? kbc is communicating with the touchpad via ps/2 lanes? i'll test with scope later this evening here in germany. i'm not home atm.

there is no firmware available for the kbc and if i try to write or read with i/o programmer kbc inserted in external board, it can't read the chip id (the programmer is working fine. is use it frequently). i tried 3 different kbcs and these do not seem to be programmable at all. but maybe you are right. on the other hand the firmware should be available online somewhere, but like is said, i can't find any rom out there. will report later then! thanks again

it's getting hilarious. while i was touching the ec_tpclck line with scope the singal recovered. all singals are up now, but tp won't work till now. i'll report later... this makes no sense at all, hahaha

[rediii]

Re: acer vn7-791g - 14203-1m - wistron - touchpad dead

well i'm going to replace the usb serial controller now... after that i'm out. have to order it sadly, thanks for your help mon2