Replacing array member on the fly (big LCD characters idea)

[CuriousOne]

Yes, there are 8 custom characters and char #255 - Full block is used.

[CuriousOne]

Here's 2x2 font for 1602 OLED (Here you can write bytes directly, not limited by 8 custom chars).

[CuriousOne]

Wanted to store above font in EEPROM. each character takes 2x13 bytes. so 260 byte of memory are needed, but most chips have only 256 bytes of eeprom available.
I come up with run length encoding compression idea. Since there are only 5 bits used, can use remaining 3 as a counter, showing how many times current pattern should be repeated. This gives ability to repeat up to 8 positions

Say for character 4 (top left part), in "normal" mode, bit pattern looks like this: %11000. But if we add %110 to end of it, so it now looks like %11000110, decoder software will know that it have to repeat that pattern 6 times.

So code for reading and decoding char to appropriate DDRAM or whatever it is called, should work like this:

1. Set pointer address from which the bitmap should be read.
2. Read it, if 3 last bits<>0 then separate it, and do the loop, writing the code of first 5 bits, repeating them times specified in these 3 bits.
3. Continue reading of bitmap as needed.

But I have issue with statement for dividing bit variable into two. Say I have %10101010. How should I divide it into two variables, one which has 5 bits from left, and another having 3 bits from right?

[Ioannis]

But I have issue with statement for dividing bit variable into two. Say I have %10101010. How should I divide it into two variables, one which has 5 bits from left, and another having 3 bits from right?

Something like this?

byte_var    var byte
a_left         var byte
b_left         var byte

byte_var=%10101010
a_left=byte_var & %11111000
b_left=byte_var & %00000111

Ioannis

[CuriousOne]

Yes, but I was thinking about either <<, >> or DIG() operators...

[Ioannis]

then combine accordingly like that:

a_left=(byte_var & %11111000)>>3

to make it right justified if needed.

Ioannis

[CuriousOne]

Found interesting thing. On power up, custom character area in normal LCD are empty, but on WS0010 OLED displays, they are filled with random numbers on power up.

[CuriousOne]

Just did a rough estimation - the above idea should save 30-40% of EEPROM space. Not bad.

[CuriousOne]

Also it is possible to separate and replace some similar blocks with additional indexes - this should save additional 10-20%...