Noise/Glitch Problems with Mikro HMI (7") - FT813 chip

[signalflow]

Hi, I am using this Mikromedia 7" HMI (Capacitive) touchscreen
https://www.mikroe.com/mikromedia-hmi-70-cap

It uses the FT813 graphics chip and has an FT90x microcontroller.

We really want to use this display (buy thousands of units) but we have been stuck on one problem and can't seem to get past it.

If the display is used in equipment that has inductive loads (pumps/motors/contactors) that are turning on/off, then the display is very susceptable to noise spikes and will not function properly. What I suspect is happening is the !PD (reset or power down) line on the FT813 is getting a tiny glitch (pulse low) on it due to the noise spikes and once that happens the intialization is ruined. Or if a command is being sent from the FT90x to the FT813 such as for displaying text or a button, and there is a tiny glitch on one of the SPI lines and the FT813 receives a bad command because of it, then it garbles the display. Most of the time, the HMI has to be powered down and restarted. The FT813 cannot filter out bad commands being sent to it as far as I can tell.

I had the same problem with the ConnectEve (Mikroe) and the FT800 graphics chip (same thing just resistive touch and lower resolution). Using a ferrite on the ribbon cable powering the 7" HMI and helps a little but still has unacceptable behavior that makes the HMI unusable. Added a small capacitor to the PD line helped a little as well (on the ConnectEve, so I might try this on the 7" HMI).

Has anyone else solved this? It just seems that this FT813 is a totally useless graphics chip in a real environment as far as I can tell so far. I contacted FTDI and they were no help at all. Hoping Mikroe can help.

One idea is to read in the FT813 chip ID and if not valid then force a reset/re-initialization of the FT813. This would just look bad to the user (having their screen reset on them when they turn a pump, motor or contactor on/off). It also does not fix the issue where text will be garbled on the screen (and stay there).

[dusan.poluga]

Hi,

Are you isolating your signals with optocuplers and are you shielding the display to prevent interferences ?

Best Regards,