Hello all

I have a small project where I thought that I could use existing inexpensive 2.8” tft as display. The Arduino shield in question utilises ili9341 chipset. Obviously this setup would require fbtft module and spi drivers installed. This kind of displays have been around in the raspb scene.

Tried to locate fbtft spi but did not have much success. Is it necessary to get kernel sources+fbtft source from git and do the compile to get this display to work? Is there some other display which could be used a bit more ’out of the box’. Are the spi drivers in the image?

I am looking mostly frame buffer -type functionality and possibly some kind of elementary touch detection.. so full X is not needed.

Another question about serial ports. In the manual there is a debug port (tty3 ?). Is it possible to use this port from application? It seems that OS sends some kind of data at boot.

Regards aku

fbtft is part for the Linux kernel for a long time, but only as a "staging" driver. That means its code had - and apparently still has - significant quality issues. We do not enable staging drivers for the IOT2050 kernel, but you can build your own image with a custom kernel configuration (e.g. some changes to https://github.com/siemens/meta-iot2050/blob/master/recipes-kernel/linux/files/iot2050_defconfig_extra.cfg) and try out if that driver works for you.

But: You likely need additional device tree adjustments in order to explain the driver how the display is attached. That may not be trivial, though, also due to the multiplexed pins that are connected with the SPI bus. Using iot2050setup to configure the multiplexed pin on-the-fly may help, but the proper way would a description via a device tree extension.

Regarding the debug tty: You can tell the kernel to not use ttyS3 as console (kernel command line adjustment). Edit /etc/default/u-boot-script and run update-u-boot-script afterwards. But be careful, you may render the image unbootable.

Ok and thanks for the info.

Maybe I am not willing to go into the kernel internals at this time. So I purchased today a Joy-It SBC 20*4 lcd display with i2c interface. Let’s see if there is any better luck with this one :)

BTW, gpio ports seem to work okay with supplied system software. Same test program was used (Intel c examples) as with iot 2040. Checked mraa ports 0..19 as inputs and port 8 as output. All ports were configured as gpio ports.

regards aku

Yes, this character based unit was almost like a piece of cake.  Connected four wires and ”i2cdetect -r -y 4” command  showed the display at address 27. However, I had to change jumper X83 to 1-2 (=5V) position because I was getting numerous i2c bus errors. Tried also to operate the display at 3.3V- worked- but it was too dim. Thought that changing the jumper it is not necessary for the i2c bus. These Hitachi based character displays are nothing new - I think have seen similar displays at least 30 years ago. Updating speed is a bit slow compared to modern devices.