TrxAVR-Picastar - TFT colour

TFT colour display development - TftAVR

TrxAVR supports a 480x272 colour TFT display with touch panel..

For screenshots from TrxAVR-Picastar see: Colour TFT screenshots.

The TrxAVR code to drive these display was developed using an eDIPTFT43-ATP 480 x272 intelligent
colour display from Electronic Assembly. These cost 200ukp. A few builders use these.

A large number of builders are using the TftA display driver board which was developed to provide
a low cost way of achieving a 480x272 colour Tft display.

The initial development using the EA display is described further down this page

TftA - achieving a low cost TFT display

480x282 colour TFT displays can be abtained on eBay for as little as 20ukp. The displays used are
4.3 inch (as the EA display) or more commonly 5inch. They can have an optional touch panel.
They are mass produced for use in GPS navigator units etc.
The total cost is in the order of 30ukp + display cost.

This controller board project is named TftA. (The protoype was TftAVR)

Glenn, VK3PE has provided an excellent description / construction manual for TftA at:

http://www.carnut.info/tftpcb/tft.htm

Further construction information and the software is on the TftA_Central yahoo group

I therefore make no attempt to repeat Glenn's information here. - Just some useful backgroud information:

Chris Stake designed the TftAVR board using an Epson S1D13781 display driver chip and an
Atmel ATXmega128A1 processor. This board is too small and intricate for home PCB manufacture.
Gerard, VK3CG has so far (Feb2011) supplied over 190 PCBs, some with S1D13781 chips of more complete
kits of parts.
TftA communicates with TrxAVR using the I2C, two wire interface, and uses the same command sequences
as used with the EA displays. Therefore, identical, standard TrxAVR-Picastar code will drive both the EA
and the TftA controllers.
Initially (prior to feb 2011) The I2C address was fixed at hex 6F in TrxAVR code abd TftA code.
It is now stored TftA Xmega User Signature Row flash an in the 24LC512 EEPROm in TrxAVR.
If can be changed from Hobact. See : User Signature Row and TftA I2C address configuration
Gerard has done the TftA programming. This code is written in C using Atmet Studio4 /WINAVR.
It does not attempt to emulate the extensive firmware of the intelligent EA display. It simply to performs
those functions needed by TrxAVR-Picastar.

There is the need to load fonts etc into the flash memory on the display controller board (both for EA and TftA).
This can be done in a single operation from Hobcat.
(The route is: PC file > Hobcat > USB > TrxAVR > I2C > TftA )
This has removed the need for a separate programmer (thus keeping costs down)

Epson S1D13781

TftA uses a very recent display driver chip from Epson. this is the S1D13781. The development was done
on samples which were begged from Epson agents before the chips were commercially available.
Most of the S1D13781s have been been bought in bulk purchases from Rutronik UK. The price is aprrox. 6.00ukp.

TftA controller board

Full construction infomation at: http://www.carnut.info/tftpcb/tft.htm

TftA top view ATXmega128A1 on the left. Epson S1D13781 on the right

TftA components include:

Epson S1D13781 display controller
Atmel ATXmega128A1 32Mhz microcontroller
Atmel AT45DB321D 4Mbyte I2C flash memory (fonts etc)
(Supply problems lead to support for 16Mbit and 8Mbit flash memeory devices)
CAT4240 invertor for display illumination
Voltage regulators
Display connector
Mosfets for I2C bus connection

Programming the display flash memory

The flash programming code is in a zip files on the downloads page.
It is also distributed by HobcatSetup.exe.

eDIPTFT43-ATP uses file TfteDIPTFT43A.df in zipped folder: TfteDIPTFT43A_flash_125.zip
TftA uses file TftA.df in zipped folder: tf_font_100.zip

It is possible to program the display via its I2C interface.
I have therefore created a TFT flash programming window in Hobcat.

Hobcat's display flash programming window

The flash file travr.DF is generated by the compile button in the EA Kit Editor software.
(An error report occurs because te USB programmer is not found)
trxavr.DF is currently 98kbyte. Hobcat transmits it to TrxAVR via USB and then TrxAVR
send it via I2C to the display.
- so you dont need the USB programmer and there is no interface mode switching needed.

History - initial development

The inital development display: an EA eDIPTFT43A display mounted on an optional
USB programmer back-board from EA.
This was purchased in the UK from MMS Electronics (supply of displays from Electronic Assembly).
The cost is 180ukp + VAT (plus 20ukp for the USB programmer ... if purchased with the display)
A blank (unpopulated) backboard - (same as the USB programmer) can be purchased for 11ukp.

eDIPTFT43-ATP 480 x272 intelligent colour display.

The display data sheet is: http://www.lcd-module.de/eng/pdf/grafik/ediptft43-ae.pdf

This is an excellent piece of kit ... and I cant find anything else like it on the web.

Hardware:
Most colour TFT panels (including those on offer on eBay) have a RGB scanning interface - typically
a 6 bit connection for each of Red green and Blue.
They are not intended to be connected direct to a microcontroller.
An interface chip is needed with an 8 bit microcontroller interface, display memory and scanning hardware.
Epson provide a range of such controllers.
TrxAVR-Picastar could drive such a controller .... but the eDIPTFT43-ATP makes things much easier.

The eDIPTFT43-ATP hardware includes:

A colour TFT touch panel display
An Epson S1D13A05F00A1 display controller
An Atmel Atmega1280 procressor at 16.5Mhz
An Atmel 32Mbut (4Mbybte) serial flash memory
5v/3v level convertors.

Rear view of display. The chip with the label is an ATmega1280.

It has interfaces for:

SPI - which is actually available on TrxAVRs' programming socket
I2C - two wire interface - This is used by 24LC512 serial EEPROMs.
Glenn has now added a 4 pin I2C socket to his TrxAVR boards.
RS232 (with an added MAX232) and RS485 serial interfaces.

TrxAVR-Picastar uses the I2C interface.
I2C allows bidriectional inter-processor communication using a simple two wire connection.
Eight devices can be paralleled on the bus. TrxAVR's 24LC512 eeprom is hard-wired to address 0.
The EA display defaults to address 7.

In my test rig, I interposed an additional turned pin 8-way DIL socket beneath the 24LC512 eeprom
and soldered wires to the clock, data and ground pins.
Glenn's boards provide a four pin socket for I2C.

Interfacing

The display is driven by simple ESC command sequences which can be ASCII text or binary.
I have chosen the use ASCII text.

For example:

#TA switches off terminal mode
#FR 100,100,200,200,7, fills a rectangle with colour 7
#GD 30,30,200,300, draws a line in the current line-drawing colour
#ZL 50,50 "Have a nice day" writes a left justified string at 50,50 in current font, font zoom and font colour.

TrxAVR-Picastar code contains functions to generate these commands from the C code:

etTerminalOff();
etColourRect(100,100,200,200,7);
etLine(30,30,200,300);
etString(50,50,'L',"have a nice day~");

Display Flash memory:
The display's 4Mbyte flash memory can be used to store fonts, macros (command sequences), fill-patterns, images etc.

Macros
Macros are command sequences that are programmed into the display flash memory.
The macro language supports C type arithmetic manipulations.
There are no loop structures, but the use of the i++ structure as in C allows repetive tasks to be generated
quickly by copy and paste. eg: from file trxavr.kmc

   ;DSP monitor cailbration mark, two pixel vertical lines
   ; top and bottom of each bar
   i=1
   #GD L+X2+20*i,y,L+X2+20*i,y+2
   #GD L+X2+20*i,y+GS-2,L+X2+20*i++,y+GS-1
   #GD L+X2+20*i,y,L+X2+20*i,y+2
   #GD L+X2+20*i,y+GS-2,L+X2+20*i++,y+GS-1
   #GD L+X2+20*i,y,L+X2+20*i,y+2
   #GD L+X2+20*i,y+GS-2,L+X2+20*i++,y+GS-1
       etc.......

The above is a sequence of identical command pairs.
The i++ increments i for the next pair and so simulates the effect of: for i = 1 to n

For illustration purposes, links to the two macro-language files are here.
( Do not use these links for flash programming as they might not be the latest)
trxavr.kmc trxavr_font.kmi ( *.kmi signifies a file 'included' in a *kmc file)

In the TrxAVR-Picastar C code, a macro sequence is simply called by:

etcMacro(n) where n s the macro number.

Fonts
The display comes loaded with eight fonts - two of which are big fonts for numerics (and +/- ) only.
The EA software kit includes FontConvert.kmc which will convert any Windows font into a *.FXT bitmap file
for use in the display.

TrxAVR-Picastar uses Arial14, Arial16, Arial18 and Arial20 for most of the text
and OldSansBlack 42 and 28 for the frequency display.

TrxAVR-Picastar home page