Pages: [1]   Go Down
Author Topic: Reading back from 1.44"/1.8" TFT  (Read 547 times)
0 Members and 1 Guest are viewing this topic.
IRL
Offline Offline
Full Member
***
Karma: 0
Posts: 146
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

These TFTs are well known, serial interface.

In the 1.44" TFT datasheet there is a line the read command only works with parallel interface.
i tried, but when I attempt to read data, the TFT no longer updates the display.
When I restart next time, I see the updates written to the TFT RAM tough, and they display.

How about the 1.8" TFT? Reading back from the RAM is possible or not?

The datasheets are somehow very identical, even if the chips have different manufacturer/type number.

The only other alternative is to switch to use a larger, parallel TFT with 2.5".

I want to move a cursor on the TFT with a playstation XY encoder, and for that I really need to read the pixels under the cursor, and restore them.
Logged

I also have PIC related web domain.

Offline Offline
Faraday Member
**
Karma: 87
Posts: 4960
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

You may need a bidirectional level converter like the TXB0108
https://www.adafruit.com/products/395 
Since you didn't provide any link to where you bought the display or any documentation  or library info or anything else, it is unlikely you are going to get any help on this issue until you provide something to reference.
The statement:
Quote
These TFTs are well known, serial interface.
does not relieve you of your obligation to provide reference material. You are supposed to do the leg work , not us. Give us the documentation or links or something to go on and we can go from there. Otherwise, good luck...
Logged

Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,
DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

IRL
Offline Offline
Full Member
***
Karma: 0
Posts: 146
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

http://www.ebay.com/itm/1-44-Red-Serial-128X128-SPI-Color-TFT-LCD-Module-Display-with-PCB-Adapter-/191047881658
The 1.44" TFT

http://www.ebay.com/itm/1-8-SPI-TFT-LCD-Display-Module-Serial-128-160-PCB-Adapter-Power-IC-SD-Socket-/200951258962
The 1.8" TFT

I have the 1.44" TFT working, but as said, can't read back. The 1.8" controller PDF has many pages appearing almost identical. But the line it can not read back IS NOT present.

So, I wanted to get a response if anyone has ever succeeded to read back from either one of these 1.44" or 1.8" displays.
Logged

I also have PIC related web domain.

Western New York, USA
Offline Offline
Faraday Member
**
Karma: 32
Posts: 4248
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
So, I wanted to get a response if anyone has ever succeeded to read back from either one of these 1.44" or 1.8" displays.
By wording your request this way and by not providing a link to specific documentation you are severely limiting the range of potential help.

It is quite possible that, with the proper information, someone who has never even heard of one of these devices before could help you. 

One does not necessarily have to have successfully read back information from a specific device to provide help on how to do so (although it helps).


Don
Logged

Offline Offline
Faraday Member
**
Karma: 87
Posts: 4960
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

If you have it working then why are you not posting the interface connections so we can answer your question ? One of the lines must be a R/W line. There is no OTHER line. (HIGH= READ/LOW=WRITE) at least that is how regular (non-TFT) lcds work. You haven't provided any interface connection or signal name info so I can't answer your question. (I don't see the docs at the links you posted either.
Logged

Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,
DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

IRL
Offline Offline
Full Member
***
Karma: 0
Posts: 146
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

From what i just saw in a PDF for a OLED, the serial connection is really write-only.

By the way the PDFs are available at the URLs above. I have also uploaded them to my blog for easier access (no unzip).
http://aranna.altervista.org/dragonsnest/microcontroller-projects/pic32-oled-pcb/pic32-oled-pcb-downloads/

So you kinda say, even without having used the displays, you'd be able to help?

As i say, one of the PDFs contain a line serial mode is write only, while the other doesn't.

Maybe i have to live with that, and build another circuit with a parallel controller.

How can I maintain a cursor on the TFT, if I can't read back? The only way would be to maintain a tile buffer or to use text only, but it would be complicated to code.

Logged

I also have PIC related web domain.

Offline Offline
Faraday Member
**
Karma: 87
Posts: 4960
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

http://web.engr.oregonstate.edu/~traylor/ece473/lectures/spi.pdf

Quote
SPI = Simple, 3 wire, full duplex, synchronous serial data transfer  
I was under the impression that full-duplex meant bidirectional. I could be wrong but that's what it sounds like.

http://www.totalphase.com/support/articles/200350126 
« Last Edit: March 14, 2014, 03:21:06 pm by raschemmel » Logged

Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,
DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

IRL
Offline Offline
Full Member
***
Karma: 0
Posts: 146
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Today I saw the OLED PDF explicitely metions the serial mode is write only.
Logged

I also have PIC related web domain.

Offline Offline
Faraday Member
**
Karma: 87
Posts: 4960
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Ok. My mistake. I couldn't find where it says it's write only but I'll take your word for it. So it sounds like you already know it is not possible to read back from the OLED and are asking how to do it. No matter. The only way I can think of is if you can add extra SPI based R/W RAM with a different chip select pin and write the same thing to that after each write to the OLED. You should then be able to READ back from the added ram that should contain the same data you wrote to the OLED. Because it has a separate chip select there should be no conflict with the OLED. The requirement would be that the added RAM would have to be the same or  larger capacity than OLED ram. The address you write to in the added RAM is the same address you wrote to in the OLED, wouldn't the data have to be the same ? I don't know if anyone has ever tried this but that is the only suggestion I have. Sorry about the confusion about write only but I didn't realize that when you said:
Quote
I have the 1.44" TFT working, but as said, can't read back. 
you didn't mean you were having problems reading back, but that the TFT is write only. The confusion was at my end , not yours.
Logged

Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,
DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

IRL
Offline Offline
Full Member
***
Karma: 0
Posts: 146
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Well yes I have 32K serial RAMs here but I'd need at least two and it's a lot of effort.

I was thinking maybe the 1.8" TFT would work since the line about write only is not found.


going to change to larger chip/2.4" TFT anyway.

In the meanwhie, I am wiring up the small OLED, it has all pins laid out so it can be used in parallel mode.
not so much FLASH left after adding the SD card file system, only about 30% from 32K.

Since I saw today in the OLEd pdf it is write only in serial mode, eventually all of these displays are write only in serial mode.
Logged

I also have PIC related web domain.

Offline Offline
Faraday Member
**
Karma: 87
Posts: 4960
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

The parallelel mode has the R/W line I was talking about. Also, the parallel ram concept would depend on you knowing the memory map of the display.
« Last Edit: March 14, 2014, 06:59:40 pm by raschemmel » Logged

Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,
DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

IRL
Offline Offline
Full Member
***
Karma: 0
Posts: 146
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

The parallelel mode has the R/W line I was talking about. Also, the parallel ram concept would depend on you knowing the memory map of the display.

Hmm, of course I know the memory map? I want to display a moving cursor as said above.
One solution is to maintain a smaller tiles memory, and update again, easy if it is graphics, not so easy if it is text from a font, and what if I draw lines and stuff?

I think I will just use the larger 2.4" TFT.

Why it is not possible to read back data? For a cursor it would only be a small number of pixels. All these small TFTs have serial interface only (which of course is handy for wiring).
Logged

I also have PIC related web domain.

IRL
Offline Offline
Full Member
***
Karma: 0
Posts: 146
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Since I have serial RAMs here I will try it. Thanks for the idea, 32K is just enough for 128x128 at 16bits/pixel.

They are not compatible with the TFT. First I need to write to SRAM only, then copy to the TFT.
Logged

I also have PIC related web domain.

Pages: [1]   Go Up
Jump to: