It should be a lot of blue stripes with a series of coloured pixels on the first line.
The blue stripes are the background. Because I have no SD card action yet I am going
Code: Select all
ldi r18, 0x01 ; Load 0b00000001 to show a blue stripe
nop
Code: Select all
in r18, _SFR_IO_ADDR(SPDR) ; Get a byte from the SD card for the 1bpp background bitmap
out _SFR_IO_ADDR(SPDR), r14 ; que the next byte to read from the SD card in 40 clocks time
The coloured pixels are all 16 possible combinations that one nibble in 2bpp ramTiles gives
YY
RY
GY
CY
YR
RR
GR
CR
YG
RG
GG
CG
YC
RC
GC
CC
Where Y=Yellow, R=Red, G=Green and C=Clear (the background colour either blue or black)
If that works on real hardware then I shall put my thumbs up and say "great success". That is the HARD part of tempest nailed.
It only takes 12,000 lines of ASM code to do it as well.