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ArduOS (Runtime for Arduino Uno)

This repository contains code for the ArduOS runtime and is to be flashed on compatible devices to run programs in the ArduOS bytecode format.


DISCLAIMER: The ArduOS project is not endorsed, affiliated, associated, or in any way officially connected with Arduino AG. All product and company names are the registered trademarks of their original owners.


The boot process

  1. Display a simple bootscreen with the ArduOS name and the runtime version
  2. Try to access the SD card, prompt the user to insert one, if it can't be accessed
  3. Load and display a boot logo from the SD card instead of text (/ARDUOS.BMP)
  4. Create a sufficiently sized memory-file for the runtime, if it doesn't already exist (file size: 128 MiB)
    Note: It is recommended to create this file on your PC and save it to the SD card. File creation did not work as expected on my machine. To create the memfile on Windows, use the following command (tested in PowerShell): fsutil file createnew MEM0.MEM 134217728
  5. Run /SYS/BOOT.RUN from the SD card
  6. If the runtime ever reaches the end-of-file of an executable, it will run /SYS/HOME.RUN

Required system files

Note: If any of the required system files cannot be found, the device will display a message starting with FATAL ERROR and you will need to reset the device in order to restart the system. So, make sure that these files are present on your SD card. Required system files are:

  • /ARDUOS.BMP
  • /SYS/BOOT.RUN
  • /SYS/HOME.RUN

Registers and memory

Endianness

ArduOS uses little-endian (least significant byte followed by most significant byte).

Registers

The ArduOS runtime emulates 31 general-purpose registers from R0 to R31. In addition to that, R32 and R33 both contain the least- and most significant bytes of the stack-pointer respectively. All registers have a size of 16-bits each.

Memory

The ArduOS runtime also emulates 128 MiB of RAM with addresses up to 0x3FFFFFF, containing two bytes each. Data in memory is written to and read from a memfile (usually /MEM0.MEM).

ArduOS bytecode format

A valid ArduOS bytecode file must meet the following requirements:

  • A filename ending in .RUN
  • Its contents starting with 15 bytes reading ArduOS bytecode, followed by two bytes indicating the version number of the bytecode language used in the file
  • A list of instructions starting at byte no. 17 (counting starts at zero)
    • Each instruction has a length of 4 bytes.
    • The first byte of the instruction specifies the instruction, the following 3 bytes are to be used for arguments.

The res folder contains a list of instructions and system variables both in PDF and Excel-formats. (These same tables can be found below)

Instruction set

Instr. ID mnemonic Description operand A operand B operand C sets flags
0x0 ADD add the value of A and B together and save the result in A register A register B carry
0x1 ADC add the value of A, B and the carry flag together and save the result in A register A register B carry
0x2 ADDI add a constant to the value of register A and save the result in A register A less significant byte of constant more significant byte of constant carry
0x3 ADCI add the value of A, a constant and the carry flah together and save the result in A register A less significant byte of constant more significant byte of constant carry
0x4 SUB Subtract B from A and save the result in A register A register B carry
0x5 SUC Subtract B and the carry flag from A and save the result in A register A register B carry
0x6 SUBI Subtract a constant from A and save the result in A register A less significant byte of constant more significant byte of constant carry
0x7 SUCI Subtract a constant and the carry flag from A and save the result in A register A less significant byte of constant more significant byte of constant carry
0x8 AND Logical AND with two registers, save result in register A register A register B
0x9 ANDI Logical AND with register A and constant, save result in register A register A less significant byte of constant more significant byte of constant
0xA OR Logical OR with two registers, save result in register A register A register B
0xB ORI Logical OR with register A and constant, save result in register A register A less significant byte of constant more significant byte of constant
0xC XOR Logical XOR with two registers, save result in register A register A register B
0xD XORI Logical XOR with register A and constant, save result in register A register A less significant byte of constant more significant byte of constant
0xE COM set register A to ist one's complement register A carry
0xF NEG set register A to its two's complement register A carry
0x10 SBR Set bit(s) in register (set to one where bits in constant are one) register A less significant byte of constant more significant byte of constant
0x11 CBR Clear bit(s) in register (set to zero where bits in constant are one) register A less significant byte of constant more significant byte of constant
0x12 TST compare the value of register A with 0, signed register A equality, less/greater than
0x13 CMP compare the values of two registers with each other, signed register A register B equality, less/greater than
0x14 CMPI compare the value of register A with a constant, signed register A less significant byte of constant more significant byte of constant equality, less/greater than
0x15 CLR clear register A (set all bits to zero) register A
0x16 SER set register A (set all to one) register A
0x17 MUL multiply the value of A with the value of B (both unsigned) and save the result in registers R0 and R1 (little-endian) register A register B
0x18 MULS multiply the value of A with the value of B (both signed) and save the result in registers R0 and R1 (little-endian) register A register B
0x19 MULSU multiply the value of A (signed) with the value of B (unsigned) and save the result in registers R0 and R1 (little-endian) register A register B
0x1A LSL logical shift left (all bits in register, store result in register A) register A carry
0x1B LSR logical shift right (all bits in register, store result in register A) register A carry
0x1C ROL rotate left through carry (all bits in register, store result in register A) register A carry
0x1D ROR rotate right through carry (all bits in register, store result in register A) register A carry
0x1E ASR arithmetic shift right (same as RSR, but preserves the most significant bit) register A carry
0x1F SWAP swap the nibbles of the least significant byte in register A, saves the result in register A register A
0x20 FSET sets the given flag to 1 (flags: 0/C = carry, 1/E: equality 2/G: greater than, 3/S: bit copy store) flag name/no. as specified in operand A
0x21 FCLR sets the given flag to 0 (flags: 0/C = carry, 1/E: equality 2/G: greater than, 3/S: bit copy store) flag name/no. as specified in operand A
0x22 BST save a bit from register A to the bit copy store (flag S) register A bit no. (0 to 15) bit copy store
0x23 BLD load a bit from the bit copy store (flag S) to the specified position in register A register A bit no. (0 to 15)
0x24 MOV copy the value from register B to register A register A register B
0x25 LDI load a constant into register A register A less significant byte of constant more significant byte of constant
0x26 LDR load the value of the memory address described by registers B and C (little-endian) into register A register A register B (less significant bytes) register C (more significant bytes)
0x27 STR store the value of register A at the memory address described by the values of register B and C (little-endian) register A register B (less significant bytes) register C (more significant bytes)
0x28 PUSH Push the value of register A to the stack register A
0x29 POP Pop a value from the stack to register A register A
0x2A SEB Set baud rate for Serial communication to the value of register A and B (little-endian) register A register B
0x2B SEBI Set baud rate for Serial communication to a 3 byte unsigned constant byte 1 byte 2 byte 3 (most significant byte)
0x2C SOUT output the least significant byte of register A on Serial register A
0x2D SOUTI output a constant (byte) on Serial byte for output
0x2E SIN read a byte from Serial to register A register A
0x2F RJMP relative jump by signed 24-bit integer constant (little-endian) byte 1 byte 2 byte 3
0x30 JMP absolute jump to the address described by the unsigned integer combination of the values of registers A and B (32-bit) register A register B (less significant bytes)
0x31 JMPI absolute jump to the address described by the 24-bit unsigned integer constant (little-endian) byte 1 byte 2 byte 3 (most significant byte)
0x32 CALL jump to the address described by register A and B (32-bit unsigned integer, little-endian) and push PC to the stack register A register B
0x33 CALLI jump to the address described by constant (24-it unsigned integer, little-endian) and push PC to the stack byte 1 byte 2 byte 3 (most significant byte)
0x34 RET Pop a value from the stack to PC (program counter), should be used in combination with CALL and/or CALLI
0x35 SEQ Skip the next instruction if the equal flag is set
0x36 SNE Skip the next instruction if the equal flag is not set
0x37 SGR Skip the next instruction if the greater than flag is set
0x38 SLE Skip the next instruction if the greater than flag is not set
0x39 SEQGR Skip the next instruction if the equal or greater than flag is set
0x3A SEQLE Skip the next instruction if the equal flag is set or the greater than flag is not set
0x3B BREQ Jump to the address described by bytes 1-3 (unsigned intger, 24-bit, little-endian) if the equal flag is set byte 1 byte 2 byte 3 (most significant byte)
0x3C BRNE Jump to the address described by bytes 1-3 (unsigned intger, 24-bit, little-endian) if the equal flag is not set byte 1 byte 2 byte 3 (most significant byte)
0x3D BRGR Jump to the address described by bytes 1-3 (unsigned intger, 24-bit, little-endian) if the greater than flag is set byte 1 byte 2 byte 3 (most significant byte)
0x3E BRLE Jump to the address described by bytes 1-3 (unsigned intger, 24-bit, little-endian) if the greater than flag is not set byte 1 byte 2 byte 3 (most significant byte)
0x3F BREQGR Jump to the address described by bytes 1-3 (uint, 24-bit, little-endian) if equal flag or greater than flag is set byte 1 byte 2 byte 3 (most significant byte)
0x40 BREQLE Jump to the address described by bytes 1-3 (uint, 24-bit, little-endian) if equal flag set or greater than flag is not set byte 1 byte 2 byte 3 (most significant byte)
0x41 RBREQ Jump to the address described by registers A and B (32-bit uint, little-endian) if the equal flag is set register A register B
0x42 RBRNE Jump to the address described by registers A and B (32-bit uint, little-endian) if the equal flag is not set register A register B
0x43 RBRGR Jump to the address described by registers A and B (32-bit uint, little-endian) if the greater than flag is set register A register B
0x44 RBRLE Jump to the address described by registers A and B (32-bit uint, little-endian) if the greater than flag is not set register A register B
0x45 RBREQGR Jump to the address described by registers A and B (32-bit uint, little-endian) if equal flag or greater than flag is set register A register B
0x46 RBREQLE Jump to address described by registers A and B (32-bit uint, little-endian) if equal flag set or greater than flag is not set register A register B
0x47 PXL draw a single pixel at X=register A; Y=register B; color=register C register A register B register C
0x48 SCLR Fill the whole screen with the color of the value of register A register A
0x49 SCLRI Fill the whole screen with a constant color (values of bytes 1 and 2, little-endian) byte 1 byte 2 (most significant byte)
0x4A TSIZ Set text size to the value of register A (least significant byte only) register A
0x4B TSIZI Set text size to a constant byte 1
0x4C TCOL Set text color to the value of register A register A
0x4D TCOLB Set text color to the value of register A and background color to the value of register B register A register B
0x4E TCOLI Set text color to vaue of 16-bit unsigned constant byte 1 byte 2 (most significant byte)
0x4F TWRAP Set text wrap to true if the value of register A is not equal to zero (A != 0) register A
0x50 TWRAPI Set text wrap to true if the value of byte 1 is not equal to zero (byte 1 != 0) byte 1
0x51 TCPOS Set the cursor position for text to the values of register A (X) and register B (Y) (unsigned integer) register A register B
0x52 TOUT Print a character (least significant byte of register A) to the screen register A
0x53 TOUTI Print a character (byte 1) byte 1
0x54 IMG Draw an image file with it's path specified by a null-terminated string at a memory address specified by registers A & B at the cursor position register A register B (most significant bytes)
0x55 IMGI Draw an image file with it's path specified by a null-terminated string at a memory address specified by bytes 1-3 at the current cursor position byte 1 byte 2 byte 3 (most significant byte)
0x56 FEXISTS Set register A to 1, if file with path located at memory address specified by reg B & C exists (null-terminated string) register A register B register C
0x57 FMKDIR Set reg A to 1, if directory with file path located at memory address specified reg by B & C exists (null-terminated str) register A register B register C
0x58 FOPEN Open file with path located at memory address specified reg by B & C exists (null-terminated str), if unsuccessful set A to 0 register A register B register C
0x59 FREM Set reg A to 1, if the file with path located at memory address specified reg by B & C could be deleted (null-terminated str) register A register B register C
0x5A FRMDIR Set reg A to 1, if the directory with path located at memory address specified reg by B & C could be deleted (null-terminated str) register A register B register C
0x5B FNAME Set register A to the byte value of the Xth char in the filename (X = value of register B) register A register B
0x5C FAV Set register A to the number of bytes available to read register A
0x5D FCLOS close the currently opened file, automatically invoked by open
0x5E FFLUS flush the file (ensure that all written bytes are also physically written to SD card)
0x5F FPEK read a single byte from the SD card to register A without advancing to the next one register A
0x60 FPOS save the current position in the file to registers 0 and 1 (little endian, unsigned long)
0x61 FSEK go to a position in the file specified by registers B and C (little-endian, unsigned int), set reg A to 1 on success, to 0 on failure register A register B register C (most significant bytes)
0x62 FSEKI go to a position in the file specified by byte 1-3 (sets bit copy store to 1 on success, to 0 on failure) byte 1 byte 2 byte 3 (most significant byte) bit copy store
0x63 FISDIR set register a to 1, if the currently open file is a directory, otherwise set register A to 0 register A
0x64 FNEXT opens the next file in the current directory (sets bit copy store to 1 on success, to 0 on failure); will always switch the current file
0x65 FREW return to the first file in the directory (opens the first file on next call to FNEXT)
0x66 FOUT write the least significant byte of register A to the file register A
0x67 FOUTI write a constant byte to the file byte 1
0x68 FIN read a byte from the file to register A register A
0x69 SET set a system variable (least significant byte of reg A) to the values of registers B and C (register C might not be accessed depending on the variable) register A register B (least significant bytes) register C (most significant bytes)
0x6A SETI set a system variable to the values of registers A and B (register B might not be accessed depending on the variable) sysvar ID register A (least significant bytes) register B (most significant bytes)
0x6B GET get a system variable, save to registers 0 and 1 register A
0x6C GETI get a system variable, save to registers 0 and 1 sysvar ID
0x6D RUN change the currently running program to the one with it's executable path described by the null-terminated string at memory address by reg A & B register A register B (most significant byte)
0x6E TFT save the current touch position to registers 0 and 1, the x position to r0 and the y position to r1 bit copy store

(All following rows of the table up to instruction ID 0xFF are empty.)

System variables (sysvars)

Sysvar ID meaning get set
0 free system memory (physical RAM) x
1 screen width x
2 screen height x
3 screen width modifier
4 screen height modifier
5 x-offset
6 y-offset
7 currently used file (value must either be 1 or 2)
8 screen orientation (value must be 0, 1, 2 or 3)
9 result of micros() x
10 result of millis() x

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