Processor power?

[steved]

Bit of an open-ended question here - I'm trying to get a feel for how much processing power I'll need to provide a responsive display using uGFX.

Looking at the Displaytech INT070ATFT-TS, which is a 800x480 display with touch screen, using the SSD1963 controller and MAX11802 touch screen interface.

The graphics side is pretty undemanding - mostly simple coloured boxes with text in them - no images and no animation, and little user interaction.

Main need for responsiveness comes when the user is entering configuration data, which I envisage being a selection of the elements supported by GWIN - radio buttons, checkboxes, lists and some numeric entry, with data entry solely by touch screen.

The processor will be doing very little apart from servicing the display - a modest amount of I2C comms and that's all.

I've used the ST 32F051 with ChibiOS on another project, so that processor, or if necessary a more powerful one from the 32F family, is the favoured choice provided its likely to be adequate.

Can anyone give any advice based on practical experience?

Thanks

[Joel Bodenmann]

Hello steved and welcome to the community.

The major performance "issue" you will face is the actual interface speed between you and your display controller. 800x480 are quite a lot of pixels that need to be handled. Within our algorithms, we try to just modify the area which needs to be (no complete screen redrawings). However, if you build some GUI inteface like

where you clear the complete screen often, you will still observe quit a long build-up time if you use a slow interface. The display controller used in the video is an SSD1963 as well, but in 8-bit mode. Using the 16-bit mode instead would lead to a very big performance gain.

Long story short: Choose a microcontroller which provides a fast parallel interface to talk to your SSD1963. Every STM32F1xx and STM32F4xx MCU does provide a 16-bit FSMC interface. Make sure you get a package with enough pins for all your stuff as the FSMC will eat up 20 pins (watch out for pin collisions!)

If you can afford it (no mass production etc), go for some STM32F407 instead of an STM32F1xx as that one runs on a frequency twice as high. Also, more RAM and FLASH is never a bad option anyway. You might just need the basic elements like buttons and check boxes, but the GUI will look A LOT nicer if you blit some custom bitmaps (images) over them. With 1MB of flash, you can store a lot of bitmaps

I hope that answers your question a bit - feel free to ask any further.

~ Tectu

[steved]

Just the sort of constructive response I was hoping for, thankyou.

Low volume project, so STM32F407 it will be.