how can I use my OLED display with ST7789v Controller?

O-Family · Joined: 23 May 2010 Posts: 320 Location: Japan

I changed the library of ST7789V to 240x320 pixels.
I don't have this LCD, so try 4 ways: landscape , portrait , upside , down.

The graphic instructions (LINE, BOX, LCDAT, etc) of BASCOM-AVR are limited to byte addressing (0-255) for LCD.

To specify a position where the screen address exceeds 255, put (1) in the variable [Offset256].
An address can not be drawn across 255 and 256.
If the address specification of each instruction is 256 or more, the description of the address value is the same whether 256 or 0.

dj7th · Joined: 27 Nov 2015 Posts: 14

Thanks again for adapting the driver.
I have expanded the test program a bit and provided it with waiting cycles in order to be able to follow the video display (see attachments)
Is it to be expected that BASCOM-AVR will expand the graphic instructions to value ranges greater than 255 (word instead of byte)?
Many LCD displays on the market could then be better used. In my case, I will be able to implement my text and graphic programming with a few compromises . Very Happy

O-Family · Joined: 23 May 2010 Posts: 320 Location: Japan

I'm glad that the display was done well!
Were all four display directions normal?

The problem that the address of the graphic instruction is limited to 255 is also reported to Mark.
However, it seems that there is no extension of word passing for graphic instructions.

Currently, there is no choice but to create a function in the original library or draw it with an offset like me.
If you devise the screen configuration, it will not be too much trouble!

dj7th · Joined: 27 Nov 2015 Posts: 14

sorry for my late reply.
I have tested the 4 display options and can confirm that everything works fine.
However, I have a problem:
In contrast to a display with 4 lines and 20 characters, the data output on the graphic display is much slower, which makes real-time display of measured values almost impossible. My ATMEGA328 with 8MHz internal clock seems to be overwhelmed.

albertsm · Joined: 09 Apr 2004 Posts: 5921 Location: Holland

a text lcd has a built in font. most graphical lcd do not have that.
you can increase the clock speed to 16 or 24 Mhz. Or use an Xmega which goes up to 32 mhz.
or use a serial based nextion , see also the shared code section. i think the nextion is a good alternative.

dj7th · Joined: 27 Nov 2015 Posts: 14

Thanks for the advice.
My ATMEGA328 only runs at 8MHz with the internal clock. I don't want to use an external clock, as experience has shown that this leads to interference in my hf receiver. Since the circuit exists as a finished board, unfortunately no other cpu can be used.

MWS · Joined: 22 Aug 2009 Posts: 2262

SZTRAD · Joined: 30 Dec 2019 Posts: 165

What it means in "real time". How often do you need to change the contents of the display?

O-Family · Joined: 23 May 2010 Posts: 320 Location: Japan

This type of color LCD module uses an SPI interface to reduce wiring.
In addition, this library uses software SPI to freely arrange ports.
If make the library compatible with hardware SPI, you can expect some speedup, but you can not expect it.

In addition, the LCD controller sends a 1-byte command and 4-byte address for row addresses, and a 1-byte command and 4-byte address for column addresses , followed by 2 bytes color data to send to display a single dot.
In order to display one character, it requires dozens of times more data transmission than the character LCD.

Therefore, even if you increase the clock speed with 8-bit AVR, it will be quite difficult to update the full screen drawing in seconds.
I think that the fundamental countermeasure is to control using many ports in a parallel data type module.
I devised a program to divide the update of the character string of each part into time division and display it with a time lag.

MWS · Joined: 22 Aug 2009 Posts: 2262

SZTRAD · Joined: 30 Dec 2019 Posts: 165

As written correctly MWS da can change the frequency of the RC oscillator upwards, but I would be careful to go outside the recommended frequency given by the manufacturer. The frequency is used not only for EEPROM but also for Flash and may not be able to change it back in the program.
O-family uses if he understood correctly 16-bit RGB, ie for a complete rewrite it needs to transfer 1,228,800 bits purely for data (320x240x16 bits). If I count on moving one bit 6 the instruction will get to the time 0.9216 seconds (if I count correctly). Data preparation is not counted at this time, so the time will be extended.
I see the acceleration of redrawing in the possibility of changing only what I need to change, as indicated by MWS. Or if I display the number 3.26 and need 3.21 I will only change the last number. It is longer to write in the program, but again the speed will increase significantly. That's why I asked what real time means for interviewers.
Of course, it would be much better to use xmeg and direct connection via DMA memory and SPI when the operator interface is outside the program itself. Or use a smart display like the already mentioned nextion.
RS

dj7th · Joined: 27 Nov 2015 Posts: 14

Many thanks to everyone who has published information here.
In my next project I will consider these recommendations.
In the current project I will do a test with the 2.8 "Nextion display.
I think this is the most effective solution.

MWS · Joined: 22 Aug 2009 Posts: 2262

MWS · Joined: 22 Aug 2009 Posts: 2262

dj7th · Joined: 27 Nov 2015 Posts: 14

Hi WMS
sorry, but i would still like to reply to your completely inappropriate comment.
I am extremely grateful to O-Family for his support, even if it did not lead to the hoped-for success.
Many thanks for the hint from albertsm to use the Nextion display. That helped me a lot.

To my person:
I'm 77 years old and unfortunately not a skilled programmer, but more at home in hardware.
For over 10 years, BASCOM has been a tool that I could learn quickly and that I have been able to use without any help until now.

Stay healthy and pass on your knowledge