Interfacing Resistive Touch-Screen Panels with a Microcontroller

[AceOfHearts]

Hello everyone,

Once again, I am counting on some sound advice from members of this very helpful forum.

After getting over the hurdle of learning to program Graphic LCDs, I am now stuck at my next big challange: Interfacing a 4-wire resistive touch screen panel over my Graphic LCD.

I have learned how the touch screen works, it seems simple enough. But where things have gotten complicated is how I would connect it to my microcontroller.

Now, I have purchased a ADS7843 and have even paid a lot of money to convert it to DIP. I have read the datasheet, but am puzzled as to why there are so many pins which are not making any sense to me (right now). I tried reading the datasheet but it all seems very puzzling it does not seem to explain things in plain terms.

I need some guidance on how best to interface such a touch-screen to a microcontroller. If using the ADS7843 is the best way, atleast some "plain english" explenation on how this chip works?.

I have seen Youtube videos of what I am trying to achieve (simple touch location recognition), Im sure you all know the feeling when you are stuck but know its possible! Hope someone knowledgeable in this area will show me the way to move forward a bit.

Regards.

 

[rezer]

Now, I have purchased a ADS7843 and have even paid a lot of money to convert it to DIP. I have read the datasheet, but am puzzled as to why there are so many pins which are not making any sense to me (right now). I tried reading the datasheet but it all seems very puzzling it does not seem to explain things in plain terms.

Pins 2-4 will connect to your touchscreen. It uses four pins for communicating with a microcontroller (serial bus -- pins 12-16, pin 13 is used for handshaking). In3/In4 are analog inputs to the ADC. You probably won't need these. A 10KO pull-up resistor is required on pin 11. Is this what you were looking for?
For actual specifics you might contact TI and see what kind of training/tutorials they may have.

 

[AceOfHearts]

Pins 2-4 will connect to your touchscreen. It uses four pins for communicating with a microcontroller (serial bus -- pins 12-16, pin 13 is used for handshaking). In3/In4 are analog inputs to the ADC. You probably won't need these. A 10KO pull-up resistor is required on pin 11. Is this what you were looking for?
For actual specifics you might contact TI and see what kind of training/tutorials they may have.

Thanks. Well I have no idea what kind of serial data it is, what format it is, what these mean, and the general operation of the whole device. At the moment, theres too many unknowns.

I suppose I gotta keep at the datasheet until something starts to click.

Thanks though.

 

[crutschow]

The I/O is a basic serial two-wire clock/data connection. It consists of a DIN external clock input, a CS enable input to start the conversion, a DIN serial input for control data ( 8 bits per Tables IV sent before each conversion) and a DOUT for the A/D output data. The input and output data is synchronized to the clock.

Basically, in operation you generate a low CS signal to start the conversion, input the 8 control bits, and then read the A/D digital output word.

The ADS7834 is operation is not simple, but it appears fairly straight forward. Just keep reading the explanations along with the diagrams. The information is all there, if perhaps a little cryptic in spots. Try to digest a little at a time. Read a small part and refer to the diagrams until you understand that portion. (Sometimes it's easier if you make a separate copy of the diagrams so you can more easily refer to them while reading.) Generally every sentence conveys an important piece of information. Skipping or skimming some of the data sheet often results in missing something important. Technical data sheets are usually written in a sparse syntax with few filler words or elaboration. It is in "plain english" but probably only to an engineer.

This is not something you can necessarily expect to understand in an hour or two. The old gray matter needs to be really exercised. Eventually it all will make sense.

If you get hung up on a particular question, place a post and someone can likely help.

And once you understand this device, understanding the next one will be a lot easier.