Electronic – Microcontroller requirements for TFT display

This is a difficult problem. Normally when you run a wide cable full of single ended signals with 1nS rise time, you can expect high supply/ground currents and high radiated noise. I am not surprised you can hear the video content on your audio.

Every EMC Engineer ought to have a book by Mr Henry Ott in their bookshelf. OK I don't, but I remember what he wrote back in the early 80's and it has served me well.

Let me recall some relevant topics.

Conducted Noise

• Isolating Analog and Digital ground currents
• Low ESR caps
• multi-point grounds

Radiated Noise

• Common-mode ferrite filters ( lossy noise absorption )
• Shielding, shield termination and shield transfer impedance
• ground planes
• optimal driving impedance
• controlled impedance cable and terminators
• interleaved grounds or twisted pair
• standing wave effects

I recall the biggest radiation on ST506 device FCC testing was always the interface 50 wire ribbon cable.

If you were to pick the top 2 of each list and implement an appropriate fix, I would hope these will eliminate your problems. If you use ribbon cable I would find a flat bar ferrite sleeve to absorb the radiating noise and locate it near the transmitting end or a clamshell sleeve just like on all VGA cables. The ferrite beads help on differential noise but not CM noise radiation. I think this fix is a must have. Laptops will usually have a flat ferrite layer somewhere over the LCD ribbon cable.

I probably missed a few topics but I don't believe buffers will help your issue unless they are ECL differential.

The INT057ATFT uses an SSD1961 controller, whose I/O can be configured in Motorola 6800 mode or Intel 8080 mode. So if your microcontroller has an 8080 type interface you can connect it without problems. But also a microcontroller without external address or data bus can talk to the LCD controller, of course.

The left side connections are the only ones you should look at. The ones on the right are the controller's business; you don't have to worry about those. That's very different from the TM056KDH01 you refer to in a comment. That's an LCD controller which needs continuous data, combined with vertical and horizontal sync. You can compare it somewhat with video + sync: if you stop supplying a video signal you won't have a picture. Only here you have 18 digital lines instead of one analog. The SSD1961's microcontroller interface runs asynchronous of the LCD refresh. You just have to fill the buffer.

There are a couple of control lines, like D/C (Data/Control) select, R/W and enable, which will be familiar for users who have worked with text LCD modules with a 44780 controller. The SSD1961 datasheet has a list of commands you can use to configure the LCD. You supply the commands via the 18-bit data bus. That allows to send a complete pixel data of 3 x 6 bit (RGB) simultaneously. An 8080 microcontroller only has an 8 bit bus, and you can configure the device to use only 8-bit; the unused data lines should remain floating. In 8-bit mode you need less I/O pins on you microcontroller, but each pixel will need three successive writes.