I have been a bit busy these days but I managed to solder the base board for the 7 inch LCD and another 5 inch base board for further testing. One good thing about this project is that the base board for the 5 inch LCD can be used with a 4.3 inch LCD with no modifications at all.
Here you can see the 7 inch being used with a Raspberry Pi Zero, the Arduino was wired for other test and left there.
Here for a size comparison I show you all the LCD's I have tested, the top one being used by the Raspberry Pi zero is the 5 inch with the HDMI module (yellow board), the 7 inch is on the left used by the arduino and the one on the right is the 4.3 inch used with the arduino. The two LCDs connected to the arduinos have the SPI module on the back (red board).
Next I show you here a small side by side test run with the 3 LCD's working together, the touch screen is working with the SPI video module (red board) but not yet with the HDMI board, that is one of the next steps. If you see the detail picture of the yellow board, you will see some missing components that are there to translate the touch screen to USB.
I found some image quality issues with the 7 inch base board, I think the length of the H_SYNC, V_SYNC and color lines is the problem. With the SPI video module this is not an issue because the frequency is much smaller than with the HDMI, a detail to take care for the next version of the base boards.