195 Tiny Pixel Processor :: Quicker, easier and cheaper to make your own chip!

How it works

Tiny Pixel Processor is a custom processer designed to procedurally generate graphics.

Specifications:

640x480 VGA Output
64x48 pixels resolution
16-bit custom instruction set
8 registers (4 general purpose, 4 read-only)

Instruction set

The processor uses a custom 16-bit instruction format, which is designed to be simple and efficient for graphics generation. The instruction set includes operations for arithmetic, logic, and control flow, as well as special instructions (sin, ramp, saw, rand) for generating procedural patterns.

EBNF
The assembler language for this processor consists of several instruction types, each with their own syntax (look at the later code examples).

Shader = {Instruction "\n"}.
Instruction = Type0 | Type1 | Type2 | Type3 | Type4 | Type5 | Type6 | Type7.

Type0 = "NOP".
Type1 = "SET" RDestination Immediate [Condition].
Type2 = ( "SL" | "SR" ) RSourceDestination Immediate [Condition].
Type3 = "MOV" RDestination RSource [Condition].
Type4 = ( "ADD" | "SUB" | "AND" | "NAND" | "OR" | "NOR" | "XOR" | "SIN" | "RAMP" | "SAW" ) RSourceDestination RSource [Condition].
Type5 = "COMP" RSource RSource [Condition].
Type6 = "OUT" RSource [Condition].
Type7 = ( "FH" | "TT" | "Credits" | "FlagP" ) RDestination [Condition].

Condition = "EQ" | "LT" | "GT"
RSource = "R" ( "0" | "1" | "2" | "3" | ( "4" | "X" ) | ( "5" | "Y" ) | ( "6" | "T" ) | ( "7" | "R" ) ).
RSourceDestination = RDestination.
RDestination = "R" ( "0" | "1" | "2" | "3" ).
Immediate = "#" 0 ... 63.

Instruction Type 0 (for NOP)

OP	Unused
5 Bit	11 Bit

5 Bit OP-Code
11 Bit Unused
16 Bit Total

Instruction Type 1 (for SET)

OP	RD	Immediate	Condition
5 Bit	3 Bit	6 Bit	2 Bit

5 Bit OP-Code
3 Bit Destination Register Selection
6 Bit Immediate
2 Bit Condition
16 Bit Total

Instruction Type 2 (for SL, SR)

OP	RSD	Immediate	Condition
5 Bit	3 Bit	6 Bit	2 Bit

5 Bit OP-Code
3 Bit Destination/Source Register Selection
6 Bit Immediate
2 Bit Condition

Instruction Type 3 (for MOV)

OP	RD	RS	Unused	Condition
5 Bit	3 Bit	3 Bit	3 Bit	2 Bit

5 Bit OP-Code
3 Bit Destination Register Selection
3 Bit Source Register Selection
2 Bit Condition

Instruction Type 4 (for Register-Register Operations)

OP	RSD	RS	Unused	Condition
5 Bit	3 Bit	3 Bit	3 Bit	2 Bit

5 Bit OP-Code
3 Bit Destination/Source Register Selection
3 Bit Source Register Selection
2 Bit Condition

Instruction Type 5 (for COMP)

OP	RS1	RS2	Unused	Condition
5 Bit	3 Bit	3 Bit	3 Bit	2 Bit

5 Bit OP-Code
3 Bit Source Register 1 Selection
3 Bit Source Register 2 Selection
2 Bit Condition

Instruction Type 6 (for OUT)

OP	RS	Unused	Condition
5 Bit	3 Bit	6 Bit	2 Bit

5 Bit OP-Code
3 Bit Source Register Selection
2 Bit Condition

Instruction Type 7 (for ROMs)

OP	RD	Unused	Condition
5 Bit	3 Bit	6 Bit	2 Bit

5 Bit OP-Code
3 Bit Destination Register Selection
2 Bit Condition

Instruction descriptions

OP	Usecase	Description
NOP	NOP	Does nothing
SET	SET RD Imm	RD = Imm
MOV	MOV RD RS	RD = RS
ADD	ADD RDS RS	RDS = RDS + RS
SUB	SUB RDS RS	RDS = RDS - RS
SL	SL RDS Imm	RDS = RDS << Imm
SR	SR RDS Imm	RDS = RDS >> Imm
AND	AND RDS RS	RDS = RDS & RS
NAND	NAND RDS RS	RDS = RDS ~& RS
OR	OR RDS RS	RDS = RDS \| RS
NOR	NOR RDS RS	RDS = RDS ~\| RS
XOR	XOR RDS RS	RDS = RDS ^ RS
SIN	SIN RDS RS	RDS = sin(RS)
RAMP	RAMP RDS RS	RDS = ramp(RS)
SAW	SAW RDS RS	RDS = saw(RS)
COMP	COMP RS1 RS2	sets condition register
FH	FH RD	RD = BITMAP[RX][RY]
TT	TT RD	RD = BITMAP[RX][RY]
Credits	Credits RD	RD = BITMAP[RX][RY]
FlagP	FlagP RD	RD = BITMAP[RX][RY]
OUT	OUT RS	Output RS to the VGA

ROM Instructions There are also a few special instructions that are used to load bitmap data from a ROM.

FH (University of Applied Sciences Upper Austria Logo)
TT (TinyTapeout Logo)
Credits (Project Credits)
FlagP (Flag pole)

These Instructions can be called like every other instruction (including conditionals), but they will load the corresponding bitmap according to the current pixel coordinates (RX, RY) into the destination register.

Registers

General Purpose Registers

Register 0-3 are general purpose registers that can be used for any purpose. They can be read and written by instructions.

Read Only Registers

Registers 4 (RX) and 5 (RY) contain the current pixel coordinates. Register 6 (RT) contains the current time (the count of frames divided by a programmable divisor). Register 7 (RR) contains a deterministic random value for every pixel (every frame is generated the same, so it is useful for generating a noise pattern).

The registers can only be read by the instruction, writing to them is not recommended, as it may cause unexpected behavior.

UART

To reconfigure the processor, you can send commands via UART. The following table shows the available commands:

Writing to the instruction memory

To reprogram the processor, you can send a sequence of 3 bytes via UART.

First byte: Command (see table below)
Second byte: First half of the instruction (bits 15-8)
Third byte: Second half of the instruction (bits 7-0)

Command hex	Command bin	Description
0x80	1000 0000	Addr 0
0x81	1000 0001	Addr 1
0x82	1000 0010	Addr 2
0x83	1000 0011	Addr 3
0x84	1000 0100	Addr 4
0x85	1000 0101	Addr 5
0x86	1000 0110	Addr 6
0x87	1000 0111	Addr 7
0x88	1000 1000	Addr 8
0x89	1000 1001	Addr 9
0x8A	1000 1010	Addr 10
0x8B	1000 1011	Addr 11
0x8C	1000 1100	Addr 12
0x8D	1000 1101	Addr 13
0x8E	1000 1110	Addr 14
0x8F	1000 1111	Addr 15
0x90	1001 0000	Addr 16
0x91	1001 0001	Addr 17
0x92	1001 0010	Addr 18
0x93	1001 0011	Addr 19

Configuring the Time Register Divisor

The time register contains count of frames divided by a programmable divisor. This divisor can be changed via UART and ranges from 0 to 63. Default is 5.

Command hex	Command bin	Time Counter
0x40	0100 0000	0
0x41	0100 0001	1
0x42	0100 0010	2
0x43	0100 0011	3
0x44	0100 0100	4
0x45	0100 0101	5
0x46	0100 0110	6
...	...	...
0x7D	0111 1101	61
0x7E	0111 1110	62
0x7F	0111 1111	63

How to test

The default configuration includes a simple program that generates a procedural pattern. You can plug a VGA monitor into the tiny-vga board and see the output from the processor.

If you want to program the ASIC, you can use the flash_gui.py script in the flash folder. This program allows you to parse your assembly code and upload it via COM port (USB to UART converter is needed) to the processor.

The following python packages are needed to run the script:

pip install customtkinter serial

Code Examples

Code examples can be found here.

External hardware

The tiny-vga board is used to display the output of the Tiny Pixel Processor on a VGA monitor.

Additionally, a USB to UART converter is needed to upload the program to the processor. The chip uses 9600 baud rate, 8 data bits, no parity, and 1 stop bit.

Credits

This project was created by Patrick Pollak, Julian Schlager, Thomas Lindinger, Simon Vogelhuber and Sebastian Gmeiner. The project was developed as part of a course at the University of Applied Sciences Upper Austria, Campus Hagenberg. The course and project were supervised by Prof. DI Dr. Markus Pfaff.

This project was inspired by TinyShader by mole99, originally created for the TT06 Shuttle. While TinyShader served as a conceptual starting point, we made deliberate design decisions throughout development - including our own custom processor architecture and instruction set.

#	Input	Output
0	Uart_RX	R1
1		G1
2		B1
3		VSYNC
4		R0
5		G0
6		B0
7		HSYNC

195 Tiny Pixel Processor