Need help in microcontroller/board selection

Hello,

I want to design one system which need following features.

1. Graphical/Touch screen 7inch LCD interfacing for displaying and parameter controlling.
2. Approximately 100 I/O pins.
3. Low cost.

I am confused about my selection of microcontroller/board. Please suggest me that which microcontroller/board should I use ?

You could do it with many micro's ARM, PIC... 8, 16 or 32bit.... But the bigger / faster processors will give far better usabiliy... If you use a 100 pin 8 bit and a decent LCD driver, the results on a 7" will always be too slow... If you use a 32bit running at 100Mhz +... Well!! No contest....

I use a PIC32 and a 16bit LCD interface and the results are good on a 4.3" screen....

Here is a 5" touch screen for a Raspberry Pi.
The LCD is $29 and the Raspberry Pi 3 is $35.
https://www.banggood.com/5-Inch-800...berry-PI-3-Model-B2-Model-BBAB-p-1054289.html
I can't find a 7" but I have seen them.

The Raspberry Pi 3 does not have 100 I/O pins. BUT You can get from many places expansion boards that add 8 or 16 or 32 more.

Here are three.
**broken link removed**
https://www.adafruit.com/product/2718
https://www.sparkfun.com/products/13733