I don’t think that would be possible I’m afraid doug!
Thanks jon… so you mean there is no chance at all to modify the capacitive touch screen sensitivity? Perhaps the drivers are precompiled and no configuration parameters are supplied in Raspbian Jessie?
I just spotted this note above, and found it interesting because I too was wondering what those additional jumpers were for and had never seen them documented. I’m not sure what you mean though by using them for touch when not using an RPi2 - does that mean that touch doesn’t work automatically on RPi 1 Bs? Can you elucidate more on their use?
Another area not fully documented is the power connection. Here is my take on the power connections that I’ve never seen stated in the following way:
You can power the display from two different places: the micro-USB port or the jumpers, just like you can power the RPi from either the micro-USB port or the jumpers. Therefore you have a number of combinations possible: If the display is being powered externally, you can power the RPi from the display’s USB or the jumpers. If the RPi is being powered externally, you can power the display from the RPi’s USB or the jumpers. Or you can power both externally. The official documents only show a couple of those combinations, but all are possible.
Am I incorrect in any of the above?
That’s the understanding I came to, but as I said, the guides all just tell you to connect two or four of the jumper cables and don’t really go in to any detail about why.
Not really sure from where I got it but my understanding was that on the Pi 2 the touch input goes through the ribbon cable but needs the jumpers on older models. But yea, can’t find a source and I can’t be bothered setting up a card for my old B+ and hooking the screen up to that…
With the jumper cables for power you can plug power in to either the Pi or the Display and it’ll be shared. I had it plugged in to the Pi, FAQ above days display and that worked when I tried just now.
You can also power the Pi as normal and then use a normal USB to Micro USB cable between the Pi and Display in case you can’t use the GPIO and don’t want two power supplies.
I see the backlight power commands were added to the FAQ, but not the backlight strength control?
I wrote the FAQ that exists in the Raspberry Pi docs, and here, and was in something of a rush trying to tackle the common issues so I didn’t go into much detail on this or power options.
You are correct, however, the Pi 2 has the second i2c available through the DSI ribbon cable to the LCD, so it can be used to initialise the display, control the backlight and read back touch coordinates.
The old Model A and Model B Pi’s don’t have this i2c bus, so you need to give over control of your main bus to the LCD (unfortunate if you want to use any other i2c devices) and connect SCL/SDA manually with the supplied jumper wires.
There are, as people mention, several ways of powering the display. By far the best is to use two 2A adapters and power the display/Pi individually. Yes, two mains adaptors is overkill for many setups, but it’s also great for making sure enough power is available to HATs and peripherals without ever seeing a rainbow-square-of-low-voltage. I only use one adaptor myself with our split cable, and with an external hard disk connected, so I don’t practise what I preach, but it’s nonetheless the best configuration for making the most power available.
With the Pi 3, when the new official 2.5A adaptor is available then that would certainly be the best balance of power/portability. I haven’t tested one with our split cable yet, but it’s my personal favourite setup.
So to summarise, you can ( and I have tried all of these configurations ) power the:
- display from the Pi via jumpers
- Pi from the display via jumpers
- Pi and display from separate adapters
- Pi from the display via a USB to microUSB cable
- Pi and display with a single adaptor using a Y splitter cable
The two configurations I use regularly are the Y cable, and Pi/display connected via jumpers and powered by which ever port I bother to plug it into. I have jumpers soldered to the underside of the Pi to avoid blocking the GPIO header.
You could even power the display from a USB port on the Pi, but that would count toward the USB current limit (absolute max 1.2A) shared across all USB devices so I wouldn’t ever bother.
I read that the camera ribbon can also be used just fine and that made me question can the camera hdmi extension cable be used to offer hdmi input to the display? Would be useful for the RPi zero?
Absolutely not. Don’t try this, at best nothing will happen, at worst you might fry something. The camera HDMI connection does not convert the signal to HDMI, it simply uses an HDMI cable as a convenient way to get the camera signals from A to B.
The HDMI extender will work with the display to connect it to the Pi’s DSI port, I’ve tested this myself, although your mileage may vary with different HDMI cables.
Thank you for the swift reply. I feared that was going to be the case, it seemed a far too easy way to add hdmi connectivity to the pi display! Never mind, a different display it is then. Thanks again for answering my question.
No worries! If you don’t mind tiny, the 5" HDMI display is ( adorably cute ) the same resolution as the official touchscreen and runs beautifully: https://shop.pimoroni.com/products/hdmi-5-display-backpack-without-touch
Too many people have had great success with this screen. It must just be me! I ordered one screen, installed a fresh copy of raspian, updated (including rpi-update), tried everything I could find and have had absolutely no luck getting even the slightest glimmer out of the display. I ordered a replacement and tried it today with the same results. Power is wired into the display and out to the Pi. Pi is a Model B v 1.1.
I’ve ‘triple checked’ the FPC and DSI cables and ensured I’ve got a good 5V 2A power source, yet…nothing.
I did notice, however, that I don’t have a folder labelled /sys/class/backlight/rpi_backlight/ in my system. (Was going to try and crank the brightness up to make sure it wasn’t dimmed for some reason). Any ideas on why that folder might not be present or what else could be going wrong?
as far as I’m aware it does NOT (currently) work with the any Pi prior to the B+, this is likely your problem right there.
Actually, quoting this very FAQ:
Have you tried the above?
Yes, I have tried the ignore_lcd parameter as well. And it’s not that I can’t get the touchscreen working. It doesn’t blink on at all. I have a sneaking suspicion that I’ve toasted something on the Pi.
Come to think of it, RogueM, I could’ve sworn that I saw the Pi I have is compatible. I definitely need the i2c bus for this project, so I might have to upgrade. I was a total noob to the Pi world and am finally getting my feet wet, so I had made the assumption that the model with the higher listed RAM and quad core processor was the newer version, but that’s apparently not so.
Greetings,
Where can one obtain a schematic diagram for the PI Touchscreen Display? There is a USB 1 connector on the display board I tried to use for power but no joy. A schematic might tell me why.
I’m afraid there’s no schematic available to my knowledge. Could you possibly go into more detail about your power setup? We might be able to offer an explanation!
trying to turn off LCD and everything points to using:
echo 0 > /sys/class/backlight/rpi_backlight/bl_power
echo 1 > /sys/class/backlight/rpi_backlight/bl_power
but i get the error "file/directory doesn’t exist"
I have the /sys/class/backlight dir but it is empty, also cannot create files/folder within… even with sudo?
any help would be helpful!
1 Like
That’s odd! What version of the Raspberry Pi are you using, and what OS are you running?
Do you see any clues ( errors from the display/backlight drivers ) if you open Terminal and run: dmesg?
The 7" screen is working well… but for certain development tasks I want to go back to the HDMI screen.
When I do, I find the desktop environment is changed. Specifically:
- the mouse pointer is sometimes missing, sometimes a heavy “X”
- all newly opened windows are “pinned” to the upper left.
This is not the standard behavior of the desktop under Jessie; how do I restore it?
Thanks!
How have you switched back to HDMI?