While I know the pros and cons of each type of screen and how IPS is superior to TN screens in viewing angles and color reproduction I'm trying to understand how these two screens operate differently.

After viewing the datasheets of several IPS and TN screens there are 4 pins that seem to be different between an IPS and TN screen which are below:

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While these 4 pins seem to be present in all IPS screens I have come across(though they might be numbered differently), regular TN TFT screens do not have them. I've been unable to figure out from the datasheets what purpose these pins serve. Anyone know?

I'm trying to modify a TFT HDMI decoder board from Adafruit to use with an IPS screen but these 4 pins don't match up and I'm trying to figure out what additional circuitry/modifications are required to drive them.

For reference here is a datasheet of a IPS screen:https://www.scribd.com/document/386153053/T4D0BP

And here is a datasheet of a TN TFT screen: https://cdn-shop.adafruit.com/datasheets/KD50G21-40NT-A1.pdf

  • \$\begingroup\$ Most likely and becoming more common is they are for a "backdoor" comm channel to exchange config data, error flags etc. This is common in PCIe and USB-C connections. Similar to JTAG but has an arbitrary protocol. \$\endgroup\$ – Sparky256 Aug 15 '18 at 4:39

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