SPI LCD on Pi

[apohero]

Hi there,
i bought a sainsmart 1,8" display to connect to my pi and followed the instruction here: http://www.youtube.com/watch?v=nMQJmVDgAl8
But its not working
So i wanted to know if someone already has connected a SPI LCD to the pi successfully and maybe has a simple hello world prog for testing?
thanks

apo

[jfornango]

so... right off the bat, I noticed that this screen in the video is not a sainsmart device. That will change things a bit from the vid. Also, in looking at the Pi pins in use in the video, you will notice that he is using I2C, not SPI, so your hookup and code will be completely different. (if you based your hookups on the video, that's your main problem)

I looked up the sainsmart for its pinouts, and here is what I found:
1. GND : Power Ground
2. VCC : 5V power input
3. CS : Chipselect for LCD,
4. SDA : LCD Data for SPI
5. SCL : SCLK for TFT Clock
6. RS/DC : Command/Data Selection
7. RESET : LCD controller reset, active low
8. CS (SD-CS) : Chipselect for TF Card,
9. CLK (SD-Clock): SPI Clock
10. MOSI (SD-DI) : SPI Master out Slave in
11. MISO (SD-DO) : SPI Master in Slave out

Note that pins 8 - 11 are for the SD card slot on the back of screen module and aren't discussed here.

To get SPI video, I think your GPIO hookups will work as follows: (if someone has more experience, please feel free to correct me)

Sainsmart........................RPi GPIO
1. GND..............................6. GND
2. VCC..............................2. +5 VDC
3. CS................................24. SPI CS 0
4. SDA.............................19. SPI MISO
5. SCL..............................23. SPI SCLK
6. RS/DC..........................22. GPIO 25
7. RESET.........................18. GPIO 24

As far as programming goes, I'll be honest, I'm clueless. No experience in that arena yet.

[bgreat]

Pin 19 on the Raspberry Pi is MOSI (Master Out Slave In). The MISO (Master In Slave Out) is an SPI input on pin 21.

You do want to use Raspberry Pi pin 19 MOSI connected to the LCD SDA on pin 4.

You can refer to the AdaFruit web site and GitHub for programming.

Enjoy!
Bill

[apohero]

Hi and thanks for the reply.
I found a nice page from the adafruit site mentioned http://marks-space.com/2013/01/08/raspb ... re-sensor/

Maybe I can use this to make the sainsmart display work. But I'm a little bit confused about the TFT/cs in the picture. He connected it to GPIO8(CE0). Or can I use your wirings?

[bgreat]

CE0 is Pin 24, so it is the same wiring. Just a naming difference.

One thing to note on the page you linked. The schematic is wrong for wiring the RF module. It shows the resistor in the ground path for the module. The resistor should be to the switch, but the ground should be connected directly to the RF module.

Enjoy!
Bill

[apohero]

Hi, I've connected everything said like above (just the display). I edited the code on the framebuffer line to /dev/fb0, cause i couldn't find fb1. The display seems to be initialized (i made some debug output). But i can't see anything, only the background light is flickering each time a command is send to display.

[bgreat]

/dev/fb0 is the primary display frame buffer for the Raspberry Pi. /dev/fb1 is the frame buffer for the TFT.

If you read the previous blog entry on the same site -- Raspberry Pi and TFT Display -- it covers the kernel frame buffer driver being used for /dev/fb1. Without this kernel driver, the python code from the subsequent blog entry will not work.

Enjoy!
Bill

[apohero]

Yeah exactly. I saw that kernel patch right after i posted here. Right now the pi is updating and my pc is downloading the kernel patch. I will you when its finished....

[mwilliams03]

Here is the link you should follow <which I think you have already found>;
http://marks-space.com/2012/11/23/raspberrypi-tft/
At the bottom of the blog, I also list what programs you can use to push stuff to the device.

Kamal's site will be very helpful as well, he updated the drivers for the ST7735R controller, which your TFT uses;
http://www.whence.com/rpi/


I have attached some python code that you can use to test.
It uses pygame to write to framebuffer 1.
I think Pygame is install by default on the pi image.

Plus you can edit it to display your own stuff.

Just run it with;
sudo python drawing.py


I hope this helps

[apohero]

ok so far.... I'got the following step
1. "compile the kernel" (i skipped the update things)
I cloned the kamal things, took the config from my pi and made the following configs:
ST7735 framebuffer support (FB_ST7735) [N/m/y/?] (NEW) y
ST7735 panel is ‘red tab’ type? (FB_ST7735_PANEL_TYPE_RED_TAB) [Y/n/?] (NEW) y
ST7735 framebuffer mapping to SPI0.0 (FB_ST7735_MAP) [N/m/y/?] (NEW) y
-> ST7735 RST gpio pin number (FB_ST7735_MAP_RST_GPIO) [-1] (NEW) 25
-> ST7735 D/C gpio pin number (FB_ST7735_MAP_DC_GPIO) [-1] (NEW) 24
ST7735 SPI bus number (FB_ST7735_MAP_SPI_BUS_NUM) [0] (NEW) 0
ST7735 SPI bus chipselect (FB_ST7735_MAP_SPI_BUS_CS) [0] (NEW) 0
ST7735 SPI bus clock speed (Hz) (FB_ST7735_MAP_SPI_BUS_SPEED) [4000000] (NEW) 4000000
-> ST7735 SPI bus mode (0, 1, 2, or 3) (FB_ST7735_MAP_SPI_BUS_MODE) [0] (NEW) 3

...I'm unsure with the bold ones.
The compiling, copying, blacklisting, module-inserting worked fine. Rebooted....but still no fb1 (Display is connected as usual)

The next thing i could test ist take the debian version he mentioned and make the updatethings before. I also noticed that reset and dc mismatch your wirings. Is this correct?
The line ST7735 SPI bus mode (0, 1, 2, or 3) (FB_ST7735_MAP_SPI_BUS_MODE) [0] (NEW) 3 is default 0 on my pi, not 3. I set it as above. Thats all I see... :(

[mwilliams03]

What Raspbian version are you using?
I used 2012-10-28-wheezy-raspbian.img


Try building the drivers as modules, By doing this;
ST7735 framebuffer support (FB_ST7735) [N/m/y/?] (NEW) M.

The answers you gave in bold are correct.
The diagram has RST as 25 and D/C as 24. In saying this, you can change these pins if you like, you just need to make sure that when you answer these, they actually match what is physically wired up on the Pi.
> ST7735 RST gpio pin number (FB_ST7735_MAP_RST_GPIO) [-1] (NEW) 25
-> ST7735 D/C gpio pin number (FB_ST7735_MAP_DC_GPIO) [-1] (NEW) 24


If after compiling as modules doesn't work.. send me the output of these;
cat /etc/modules
cat /etc/modprobe.d/raspi-blacklist.conf
lsmod
dmesg | grep 'fb\|2708'


And the config file you used to patch the kernel.
grep 'fb\|2708' .config

[apohero]

Hi and thanks for this perfect support!

I was using 2012-07-15-wheezy-raspbian, so its a bit older (maybe too old?). I downloaded the version mentioned in the tutorial and will make that rpi-update stuff(or can i skip that by using 2012-12-16-wheezy-raspbian/?).
I'll try that with modules switched on.

thanks again

[mwilliams03]

I havent used 2012-12-16... but someone posted this on my blog;

Ok, I finally managed it. Important: If you use raspbian 2012-12-16 DON’T UPDATE THE FIRMWARE! (don’t use rpi-update). The firmware is already new enough for the driver.
I had to set up a new raspbian-wheezy 2012-12-16 (on a slooowww 2gb sd-card) and did all steps except rpi-update. This keeps me the 3.2.27 kernel. (apt-get update; apt-get upgrade is o.k.)
Then I had to do a small modification. First I use menuconfig:

klaus@LittlX:~/src/raspberrypi-linux$ sudo make ARCH=arm CROSS_COMPILE=/usr/bin/arm-linux-gnueabi- menuconfig

The st7735 driver is in:
Device Drivers -> Graphics support -> Support for frame buffer devices
And then the driver has to be build as an module (don’ use ‘y’, use ‘M’ instead)

ST7735 LCD panel framebuffer support
[*] ST7735 ‘red tab’ panel type?
ST7735 framebuffer mapping to GPIO/SPI
(25) ST7735 RST gpio pin number
(24) ST7735 D/C gpio pin number
(0) ST7735 SPI bus number
(0) ST7735 SPI bus chipselect
(4000000) ST7735 SPI bus clock speed (Hz)
(3) ST7735 SPI bus mode (0, 1, 2, or 3)

Do the rest steps mentioned. it should work!

Reply ↓

[apohero]

hey...... my pi wants to say something...

http://postimage.org/image/qh30d6yed/

[apohero]

after i took the newest wheezy and build the kernel with the driver as module, the fb1 appeared. But the drawing example didn't cause the display to work it was just flickering. Then i rewired the pi (DC ->GPIO24 and RES->GPIO25) and voilá there was the drawin.YES!!!
Inspired by that I tried the mplayer example...and wow I was watching "wreckit ralph" (low framerate but cool).
The next things I will do is checking out why my terminal is no more reacting on "ctrl-c" when running the drawing example (or any other pygame example),and how to get the fbterm-login working (now saying that it reloads too fast and "wait 5 minutes" again and again).

Thanks a lot for the really really good help! Best support I ever got!

[gima]

Correct me if I'm wrong, but as I understand, the 3- and 4-wire serial protocols of the ST7735R are not SPI, even though the datasheet says so. They are protocols that are defined solely in the datasheet.

I found the tossing of the words "SPI" and "MOSI" misleading, and ended up creating simple, isolated demonstration on how to use the display driver. It's available here: https://github.com/gima/st7735r