brendennerd
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what screens work for raspberry pi best?

Sun Oct 23, 2016 5:19 pm

I recently switched my electronic project from arduinoto raspberry pi and as such im very in exsperanced in the pi. I was looking at ebay posts for screens and i notice that some show the raspberry pi's Linux on them. My question is what type of screens is the raspberry pi defulted to output to for these screens. Does it use spi, i2c (dout it),composite? The screens im refering to are ones like this http://pages.ebay.com/link/?nav=item.vi ... 03&alt=web
It shows the raspberry pi using Linux but it has a unspecified data type.

W. H. Heydt
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Re: what screens work for raspberry pi best?

Mon Oct 24, 2016 1:52 am

Welcome to the Forums.

I see from the link that you're looking at a 2.8" screen. It appears to be using the SPI interface, plus a couple of GPIO pins. Since that's an Adafruit screen, try checking the specs at...Adafruit. I think the Adafruit link is here: https://www.hactrn.net/ietf/rfcgen/textms.html Once you get past about 3.5" to 4" most displays connect to the native HDMI connector on the Pi.

So the full answer to the question in your subject line is: It depends on the display. There are four ways to connect a display to a Pi. One is to use the interfaces in the GPIO block. The second is to use the on-board DSI connector (the RPF 7" touch screen is the only one I know of that does that), There is a composite video output that can be used, usually with an older TV. The final way is to use the Pi's HDMI output. That last is good for pretty much anything you can imagine. I've used 19" 1280x1024, 24" 1920x1200 and 27" 1920x1080 displays with a Pi connecting to the HDMI.

Since you're coming from Arduinos, where the Arduino is an MCU that runs a single task that was compiled on a different system and then installed, the Pi is a fully featured computer that runs a multiuser, multitasking OS where programs can be written and compiled. That includes the ability to run an Arduino IDE. As such, the Pi has I/O ports oriented to uses beyond embedded systems.

brendennerd
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Re: what screens work for raspberry pi best?

Mon Oct 24, 2016 5:00 am

Ah ok thank you! So if i was to simply connect up any old spi screen i could configure it up so its used as the main display of the device. How would i go about doing this? Is there a simple edit i would have to do to the config.txt? Or is it somthing more in depth?

W. H. Heydt
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Re: what screens work for raspberry pi best?

Mon Oct 24, 2016 5:33 am

brendennerd wrote:Ah ok thank you! So if i was to simply connect up any old spi screen i could configure it up so its used as the main display of the device. How would i go about doing this? Is there a simple edit i would have to do to the config.txt? Or is it somthing more in depth?
The display supplier should have directions. The one I have from Adafruit (their 3.5") requires a specially compiled kernel, which they provide as a downloadable system image. For the one I have from Neosec I found instruction on the web that takes changes to config.txt (to enable a dtoverlay) and some parameters added to cmdline.txt. So...you're going to have to do a bit of research.

brendennerd
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Re: what screens work for raspberry pi best?

Mon Oct 24, 2016 5:38 am

Oh i see. Well the one im wondering about is a spi screen made for arduinos. Ill have to see if its possible.

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CarlRJ
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Re: what screens work for raspberry pi best?

Mon Oct 24, 2016 6:01 am

The Adafruit PiTFT screens are nice screens, and well-supported, but note that there are, I believe, nine different models under that name at this point (it's more of a family than a single device). They go something like this:
PiTFT_models_posted.png
Adafruit PiTFT models
PiTFT_models_posted.png (36.58 KiB) Viewed 3250 times
If I'm looking at the picture on eBay right (and if they borrowed the right picture), that's a PiTFT Plus #2298, with the 40-pin connector (for newer Pi's), and the resistive touchscreen and on/off backlight. You might be interested in their #2423, which is basically the same, but with a much nicer capacitive touchscreen and variable backlight.

Pretty much all the small 3.5"-and-under screens for the Pi connect to the Pi's GPIO connector and use SPI to get data to the screen. And they all need Raspberry-Pi-specific drivers in order to work. One can't hook up just any SPI-based screen and have it work, but there are many screens where either the manufacturer, or some enterprising individual, has done the work to get it supported on the Pi. A while back, a collection of drivers, Notro's Linux Framebuffer drivers for small TFT LCD display modules got added to the standard release. It used to take a specially compiled kernel to get screens like the PiTFT running, now it can be some config file tweaks (though there's still a lot of older documentation floating around that insists you need a special kernel). Anyway, it's important to find out what's necessary to get any particular display up and running, before buying. Screens from Adafruit and Waveshare are popular choices. Keep in mind that these are framebuffer screens getting sent data over SPI from the CPU. They are not especially fast.

As W. H. Heydt mentioned, the "Official 7" Raspberry Pi Touchscreen" is also quite good (and the only one that can plug directly into the Pi's DSI connector, where it gets the full effect of the GPU). The other alternative is small HDMI monitors - I've seen a few posted around here that fit on top of the Pi like these smaller screens, with a sort of U-shaped HDMI connector to plug the board/screen into the Pi; being HDMI-based they also get the full benefit of the GPU.

BMS Doug
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Re: what screens work for raspberry pi best?

Mon Oct 24, 2016 6:21 am

brendennerd wrote:Oh i see. Well the one im wondering about is a spi screen made for arduinos. Ill have to see if its possible.
You may be able to reuse your display if you can find out the details of the driver chip.

If its already in the framebuffer device tree setup then a few simple parameter changes will have your display working.

If it isn't already in then its quite a bit more complicated.
Doug.
Building Management Systems Engineer.

brendennerd
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Re: what screens work for raspberry pi best?

Mon Oct 24, 2016 6:48 am

The PiTFT Plus #2298 looks like a good one. Now im left with only3 questions to make sure its right for my project 1 will it work with a pi zero? 2 can i simply only connect up the pins that are receiving and sending the spi image data and leave the other pins empty (ill likly be using the gpio for buttons and such) and 3 are there versons with out the touch screen? Its useful but really not necessary. I also want to keep my price low if i can.

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davidcoton
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Re: what screens work for raspberry pi best?

Mon Oct 24, 2016 10:00 am

brendennerd wrote:The PiTFT Plus #2298 looks like a good one. Now im left with only3 questions to make sure its right for my project 1 will it work with a pi zero? 2 can i simply only connect up the pins that are receiving and sending the spi image data and leave the other pins empty (ill likly be using the gpio for buttons and such) and 3 are there versons with out the touch screen? Its useful but really not necessary. I also want to keep my price low if i can.
1 and 2 Yes: see Adafruit spec here
This updated design fits perfectly onto the Pi Zero, Pi 3, Pi 2 or Model A+, B+! (Any Pi with a 2x20 connector) ... This one also has all 40 pins GPIO pins brought out so you can connect a 40-pin GPIO cable underneath.
3 Maybe. I don't think you will find as good a product, as well supported, at the same or lower price, even without touch.
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BMS Doug
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Re: what screens work for raspberry pi best?

Mon Oct 24, 2016 2:53 pm

brendennerd wrote:The PiTFT Plus #2298 looks like a good one. Now im left with only3 questions to make sure its right for my project 1 will it work with a pi zero? 2 can i simply only connect up the pins that are receiving and sending the spi image data and leave the other pins empty (ill likly be using the gpio for buttons and such) and 3 are there versons with out the touch screen? Its useful but really not necessary. I also want to keep my price low if i can.
http://www.neosecsolutions.com//product ... 8&cPath=17
$20 for 320x480 using just the spi pins + one gpio for backlight control.
Doug.
Building Management Systems Engineer.

W. H. Heydt
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Re: what screens work for raspberry pi best?

Mon Oct 24, 2016 4:04 pm

BMS Doug wrote:
brendennerd wrote:The PiTFT Plus #2298 looks like a good one. Now im left with only3 questions to make sure its right for my project 1 will it work with a pi zero? 2 can i simply only connect up the pins that are receiving and sending the spi image data and leave the other pins empty (ill likly be using the gpio for buttons and such) and 3 are there versons with out the touch screen? Its useful but really not necessary. I also want to keep my price low if i can.
http://www.neosecsolutions.com//product ... 8&cPath=17
$20 for 320x480 using just the spi pins + one gpio for backlight control.
Thank you for that....It appears to answer a question I've had for a while about controlling backlight on the Neosec display.

BMS Doug
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Re: what screens work for raspberry pi best?

Mon Oct 24, 2016 11:12 pm

W. H. Heydt wrote:
Thank you for that....It appears to answer a question I've had for a while about controlling backlight on the Neosec display.
Happy to help, I hope it works for you.

I don't have a neosec display myself, I have am old adafruit one That I got working for a month or so then disconnected until I found a project that needs it. That was maybe 2 years ago so I should probably get on with finding a project for it (one of these years).
Doug.
Building Management Systems Engineer.

W. H. Heydt
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Location: Vallejo, CA (US)

Re: what screens work for raspberry pi best?

Tue Oct 25, 2016 12:53 am

BMS Doug wrote:
W. H. Heydt wrote:
Thank you for that....It appears to answer a question I've had for a while about controlling backlight on the Neosec display.
Happy to help, I hope it works for you.

I don't have a neosec display myself, I have am old adafruit one That I got working for a month or so then disconnected until I found a project that needs it. That was maybe 2 years ago so I should probably get on with finding a project for it (one of these years).
For my purpose (an electronic name badge) the Neosec has one significant advantage (besides price) over the Adafruit model. It doesn't have a partial set of header pins sticking out the back to catch on things. I realize that that is not a common worry...but use case.

tinylcd
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Re: what screens work for raspberry pi best?

Tue Oct 25, 2016 5:13 am

hello

recently we have listed display specially for pi zero without the female header

hope this may suit your requirement

http://www.neosecsolutions.com//product ... 5&cPath=28

regards
tinylcd

W. H. Heydt
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Re: what screens work for raspberry pi best?

Wed Oct 26, 2016 3:50 am

tinylcd wrote:hello

recently we have listed display specially for pi zero without the female header

hope this may suit your requirement

http://www.neosecsolutions.com//product ... 5&cPath=28

regards
tinylcd
If that's addressing my comment.... I have no problem with the female header on either the TinyLCD 35 or the Adafruit 3.5" display. Where I prefer the TinyLCD 35 is that it does not have the male header in place as a pass through for the unused GPIO pins that the Adafruit display has. Having a bunch of male header pins sticking out the back of the display is a nuisance and gets in the way.

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