Last Updated or created 2024-01-26

While ordering components for a mini C64 project I’m doing with my friend Bigred, I ordered a cheap ST7789-v2 display.

I want to make a generic pico gadget with a display, buttons and sound.
This to make a mini device for writing micropython demos.

The 3 tactical buttons are controlling the X,Y and Z axis of the rotating Cube.

Pinout:

PICO	DISPLAY
GP2	Tactical switch (other side to 3v3)
GP3	Tactical switch (other side to 3v3)
GP4	Tactical switch (other side to 3v3)
GP9	CS1
GND	GND
3v3	VCC
GP18	SCL (SPI clock)
GP19	SDA (MOSI / SPI Data)
GP20	RES (reset)
GP17	DC (data command)
GP16	BLK (backlight)

I know it says SCL/SDA (i2c) but it’s SPI controlled.

Used library : https://github.com/russhughes/st7789_mpy/tree/master

Some 3D explanation I drew a long time ago.

Using python you can use the Math funtions. (sin/cos)
Note: these are in radians!
print(math.sin(math.radians(30))) # 30 degrees

When using MachineCode you can use lookup tables.
These are generated tables which hold precalculated sin data for every degree.
You don’t have to use both cos and sin! (these are just 90 degrees shifted!)

Erik and I used a little basic program to generate an ASM include file like this

Costab LABEL BYTE
DB 0B4h,0B4h,0B4h,0B4h,0B4h,0B3h,0B3h,0B3h,0B2h,0B2h,0B1h,0B1h,0B0h,0AFh,0AFh
DB 0AEh
DB 0ADh,0ACh,0ABh,0AAh,0A9h,0A8h,0A7h,0A6h,0A5h,0A4h,0A2h,0A1h,0A0h,9Eh,9Dh,9Bh
DB 9Ah,98h,96h,95h,93h,91h,90h,8Eh,8Ch,8Ah,88h,86h,84h,82h,80h,7Eh
DB 7Ch,7Ah,78h,76h,74h,72h,70h,6Eh,6Ch,69h,67h,65h,63h,61h,5Eh,5Ch
DB 5Ah,58h,56h,53h,51h,4Fh,4Dh,4Bh,48h,46h,44h,42h,40h,3Eh,3Ch,3Ah
DB 38h,36h,34h,32h,30h,2Eh,2Ch,2Ah,28h,26h,24h,23h,21h,1Fh,1Eh,1Ch
DB 1Ah,19h,17h,16h,14h,13h,12h,10h,0Fh,0Eh,0Dh,0Ch,0Bh,0Ah,09h,08h
DB 07h,06h,05h,05h,04h,03h,03h,02h,02h,01h,01h,01h,00h,00h,00h,00h
DB 00h,00h,00h,00h,00h,01h,01h,01h,02h,02h,03h,03h,04h,05h,05h,06h
DB 07h,08h,09h,0Ah,0Bh,0Ch,0Dh,0Eh,0Fh,10h,12h,13h,14h,16h,17h,19h
DB 1Ah,1Ch,1Eh,1Fh,21h,23h,24h,26h,28h,2Ah,2Ch,2Eh,30h,32h,34h,36h
DB 38h,3Ah,3Ch,3Eh,40h,42h,44h,46h,48h,4Bh,4Dh,4Fh,51h,53h,56h,58h
DB 5Ah,5Ch,5Eh,61h,63h,65h,67h,69h,6Ch,6Eh,70h,72h,74h,76h,78h,7Ah
DB 7Ch,7Eh,80h,82h,84h,86h,88h,8Ah,8Ch,8Eh,90h,91h,93h,95h,96h,98h
DB 9Ah,9Bh,9Dh,9Eh,0A0h,0A1h,0A2h,0A4h,0A5h,0A6h,0A7h,0A8h,0A9h,0AAh,0ABh,0ACh
DB 0ADh,0AEh,0AFh,0AFh,0B0h,0B1h,0B1h,0B2h,0B2h,0B3h,0B3h,0B3h,0B4h,0B4h,0B4h
CosTabE LABEL BYTE


Basic:
0 DEF SEG = &H7000: c = 0
1 pi = 3.14159265#
2 FOR x = 0 TO 2 * pi STEP 2 * pi / 256
3 d = COS(x) * 127 + 127
4 POKE c, d: c = c + 1: NEXT

Most i learned from a book called “Art of Graphics”
(This is image of the book from the internet, i don’t think I still got my copy somewhere.