Austriker
Posts: 19
Joined: Wed Aug 26, 2015 1:18 pm

Touch Screen i2c issue

Mon Sep 14, 2015 7:20 pm

Hi,

I am having trouble with the touch part of the screen. I power the raspberry using the micro usb from the display and the jumper cables.
I have a raspberry pi 2.
The screen works nicely and the colors are really nice.
But when i tried to wire the touch with the i2c cables.
It works on start up but after that it stops working.

when i try :

Code: Select all

sudo i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- 38 -- -- -- -- -- -- -- 
40: -- -- -- -- -- 45 -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --    
but after a while when i try this again :

Code: Select all

sudo i2cdetect -y 1
Every -- is replaced by a number

I just found out that the problem comes up when i execute the i2cdetect command. I checked with an Oscilloscope looking at the SDA i2c :

when i execute

Code: Select all

sudo i2cdetect -y 1
the first time it keeps working but the second time the signal drops and the touch stop working.

I don't understand why it does this.

Sincerely,

User avatar
PeterO
Posts: 6095
Joined: Sun Jul 22, 2012 4:14 pm

Re: Touch Screen i2c issue

Mon Sep 14, 2015 7:32 pm

Which model of the PI are you using ?

You don't need to use the jumper wires on Pi2s and A+ and B+ (I think that's right) Models as the I2C connection is included in the ribbon cable between the PI and the driver board.

PeterO
Discoverer of the PI2 XENON DEATH FLASH!
Interests: C,Python,PIC,Electronics,Ham Radio (G0DZB),1960s British Computers.
"The primary requirement (as we've always seen in your examples) is that the code is readable. " Dougie Lawson

fjkraan
Posts: 1
Joined: Sat Sep 12, 2015 12:14 pm

Re: Touch Screen i2c issue

Mon Sep 14, 2015 7:48 pm

I seem to have a very similar or the same issue.

At startup of the latest Raspian the display is recognized and used, the HDMI display remains black.
When starting the X Window System, the touch screen is working, but after some time (and user activity) it stops. The behaviour is either a mouse pointer jittering vertically at the left, or no response at all. When restarting X the touch isn't working at all. Only a power cycle restores the touch screen for some time. An USB mouse can move the cursor, but the left button is not working.

At this time I am not sure this is a hardware or software (driver) issue.

I use a separate power supply cable for the display and Pi boards to a dual port USB mains charger. The Pi is a new 2B.

Code: Select all

sudo i2cdetect -y 1
complains about nonexisting /dev/i2c-1 or /dev/i2c/1.

Austriker
Posts: 19
Joined: Wed Aug 26, 2015 1:18 pm

Re: Touch Screen i2c issue

Mon Sep 14, 2015 8:12 pm

I am using the raspberry pi 2.

So i just need to wire the power and the touch should be working ?

Sincerely

User avatar
PeterO
Posts: 6095
Joined: Sun Jul 22, 2012 4:14 pm

Re: Touch Screen i2c issue

Mon Sep 14, 2015 8:38 pm

Mouse stopping seems to be fixed in the very latest firmware.. See this thread viewtopic.php?f=43&t=120642&p=815836#p815820

PeterO
Discoverer of the PI2 XENON DEATH FLASH!
Interests: C,Python,PIC,Electronics,Ham Radio (G0DZB),1960s British Computers.
"The primary requirement (as we've always seen in your examples) is that the code is readable. " Dougie Lawson

Austriker
Posts: 19
Joined: Wed Aug 26, 2015 1:18 pm

Re: Touch Screen i2c issue

Mon Sep 14, 2015 9:11 pm

Normally you don't need to wire the i2c to use the touch screen ?

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alexeames
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Re: Touch Screen i2c issue

Mon Sep 14, 2015 9:32 pm

Austriker wrote:Normally you don't need to wire the i2c to use the touch screen ?
If you have a B+, a Pi2 or an A+ you need not connect the i2c GPIO wires as they are taken care of in the DSI ribbon connector.
Alex Eames RasPi.TV, RasP.iO

User avatar
PeterO
Posts: 6095
Joined: Sun Jul 22, 2012 4:14 pm

Re: Touch Screen i2c issue

Tue Sep 15, 2015 9:18 am

alexeames wrote:
Austriker wrote:Normally you don't need to wire the i2c to use the touch screen ?
If you have a B+, a Pi2 or an A+ you need not connect the i2c GPIO wires as they are taken care of in the DSI ribbon connector.
There's an echo in here ! :D

PeterO
Discoverer of the PI2 XENON DEATH FLASH!
Interests: C,Python,PIC,Electronics,Ham Radio (G0DZB),1960s British Computers.
"The primary requirement (as we've always seen in your examples) is that the code is readable. " Dougie Lawson

User avatar
alexeames
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Location: UK

Re: Touch Screen i2c issue

Tue Sep 15, 2015 10:08 am

PeterO wrote:
alexeames wrote:
Austriker wrote:Normally you don't need to wire the i2c to use the touch screen ?
If you have a B+, a Pi2 or an A+ you need not connect the i2c GPIO wires as they are taken care of in the DSI ribbon connector.
There's an echo in here ! :D

PeterO
I know. He didn't seem to hear you, so I repeated it :)
Alex Eames RasPi.TV, RasP.iO

Austriker
Posts: 19
Joined: Wed Aug 26, 2015 1:18 pm

Re: Touch Screen i2c issue

Tue Sep 15, 2015 3:06 pm

alexeames wrote:
PeterO wrote:
alexeames wrote: If you have a B+, a Pi2 or an A+ you need not connect the i2c GPIO wires as they are taken care of in the DSI ribbon connector.
There's an echo in here ! :D

PeterO
I know. He didn't seem to hear you, so I repeated it :)
Oh sorry my bad...

Thank you for your help.

Sincerely

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