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The following tutorial walks through the steps of building a simple program in assembler to be deployed to a cartridge for Atari 8 bit computer using the CA65 assembler. Source The newest and all historic version of the source code can be downloaded from SourceForge. Main source Complete source code: HelloWorld.s. Header The header of an contains the includes as well as the exports and imports. The main source for cartridges needs to export the cartstart and cartinit procedures. cartinit is called before the OS is initialised and should return with an RTS. cartstart is jumped to after the OS is initialised and either should not return or exit with jmp (DOSVEC). .FILEOPT compiler, "ca65 V2.19 - N/A" .FILEOPT author, "Martin Krischik «krischik@users.sourceforge.net»" .FILEOPT comment, "this Atari assembly CAR program will print the “hello world” message to the screen" .INCLUDE "atari.inc.s" .INCLUDE "OS.inc.s" .MACPACK atari .SETCPU "6502" .DEBUGINFO off .EXPORT cartstart, cartinit Read only data When using the CA65 you don't need to set absolute addresses for your data. You just specify which data your want to store and how long the data is. RODATA will be stored in the ROM itself. ;; ; Our message ; .SEGMENT "RODATA" Message: .BYTE "Hello World!",EOL .BYTE "(using a cartridge in assember)",EOL Message_Len = * - Message Read/Write data If you want to write to the data you use the DATA segment which will be place in ram staring at address $2000. ;; ; Text returned from keyboard ; .SEGMENT "DATA" Input: .RES 1 Input_Len = * - Input If you want to store data in the zero page you can use the ZEROPAGE segment. Program The actual program consist of a put string which write the text „Hello World!“ and a get string to wait for a key press. It ends with a jump to DOSVEC. Put_String and Get_String are macros explained later. ;; ; main procedure ; .SEGMENT "CODE" .ORG OS::LC_8K ;; ; the main method of a cartridges does not return. ; .proc cartstart: near Put_String Message,Message_Len Get_String Input,Input_Len jmp (DOSVEC) .endproc ;; ; cartridges have an init function which is called ; before the operating system is initialized. ; .proc cartinit: near RTS ; Continue with initialisation .endproc OS macro include Complete source code: OS.inc.s Put_String This is setting all the parameters for an PUTCHR operation using I/O block 0 which by default uses the "E:" editor device. .macro Put_String Text,Len LDX #CIO::Console ;Use IOCB 0 / Console LDA #PUTCHR ; Command Put Text Record STA ICCOM,X LDA #<(Text) ; Set low byte of message STA ICBAL,X LDA #>(Text) ; Set high byte of message STA ICBAH,X LDA #<(Len) ; Set low byte of message length STA ICBLL,X LDA #>(Len) ; Set high byte of message length STA ICBLH,X JSR CIOV ;Call cio .endmacro Get_String This is setting all the parameters for an `GETCHR` operation using I/O block 0. .macro Get_String Buffer,Len LDX #CIO::Console ;Use IOCB 0 / Console LDA #GETCHR ; Command Get Text Record STA ICCOM,X LDA #<(Buffer) ; Set low byte of buffer STA ICBAL,X LDA #>(Buffer) ; Set high byte of buffer STA ICBAH,X LDA #<(Len) ; Set low byte of buffer length STA ICBLL,X LDA #>(Len) ; Set high byte of buffer length STA ICBLH,X JSR CIOV ;Call cio .endmacro Cartridge Header Complete source code: CAR_Header.s: The cartridge header are a few bytes at the end of the cartridge. This file tells the linker what to put into the header. The header is exported as __CART_HEADER__ so the linker know that this is indeed the cartridge header. .EXPORT __CART_HEADER__: absolute = 1 .IMPORT __CARTSIZE__, __CARTFLAGS__, cartinit, cartstart ;; ; set init and main run addresses ; .SEGMENT "CARTHDR" .ORG CARTCS ; cartridge start address .WORD cartstart .ORG CART ; cartridge present indicator .BYTE $00 .ORG CARTFG .BYTE <(__CARTFLAGS__) ; Init and start cartridge, no disk, no diagnostic. .ORG CARTAD ; cartridge initialise vector .WORD cartinit .assert (__CARTSIZE__ = $2000 || __CARTSIZE__ = $4000), error, "Cartridge size must either be $2000 or $4000" Makefile Complete source code: Makefile Variables A few variables describing the current project. Package_Name := Hello_World App_Name := HELLO_A Exe_File := target/$(App_Name).CAR Object_Files := target/obj/HelloWorld.o target/obj/CAR_Header.o Map_File := target/$(App_Name).MAP Include_Dir := ../../Library Assemble The assemble command needs are passed the following options: The platform you assemble for: --target atari Where include files are located: --include-dir $(Include_Dir) Creating a listing of actual code is always helpful: --listing $(basename $(@)).lst The current output file -o $(@) And the first input file $(<) target/obj/%.o: src/main/asm/%.s ca65 \ --target atari \ --include-dir $(Include_Dir) \ --listing $(basename $(@)).lst \ -o $(@) \ $(<) Link The link command needs are passed the following options: The size of the cartridge, 8k in our case: -D__CARTSIZE__=0x2000 The cartridge flags: -D__CARTFLAGS__=0x4 The platform you assemble with indication that we want a cartridge: -C atari-cart.cfg Creating a memory mapp file of linked code is always helpful: --mapfile ${Map_File} The current output file -o $(@) All the input file $(+) $(Exe_File): ${Object_Files} ld65 \ -D__CARTSIZE__=0x2000 \ -D__CARTFLAGS__=0x4 \ -C atari-cart.cfg \ --mapfile ${Map_File} \ -o $(@) \ $(+) Run on Emulator For testing and debugging the use of an emulator like the Atari800 is recommended. Deploying is much faster and can be automated inside the makefile so a simple `make run` will start the application. Note that you need to adjust the directory and file names to your system. Atari800_System := /opt/local/share/atari800 Atari800_User := "$(HOME)/Library/Application Support/Atari800" Atari800_Exe := "/usr/local/bin/atari800" Atari800_Window := -video-accel -pal -win-height 1120 -win-width 1680 Atari800_Cart = -cart-type 1 -cart "$(Exe_File)" Atari800_Option = -autosave-config -320xe -nobasic -config "$(CURDIR)/target/$(App_Name).cfg" -xlxe_rom "$(Atari800_System)/ATARIXL.ROM" run: $(Exe_File) $(Atari800_Exe) \ $(Atari800_Cart) \ $(Atari800_Option) \ $(Atari800_Window) The Atari800 emulator also has a system monitor with single step debugger and disassembler included which makes debugging that much easier. Run on device To run the application on a real Atari a hardware cartridge is needed. The best option is a modern cartridge like Side3 which uses SD cards and flash memory as ROM storage. A Side3 cost a little more then $€£100. A classic cartridge using EEPROMs will also work but is more work to setup and only slightly cheaper. For the Side3 all you need to do is to copy the CAR file onto the SD card. This operation which can be automated using make. Side3_Deploy := /Volumes/SIDE3 side3: $(Exe_File) mkdir -p "${Side3_Deploy}/${Package_Name}" cp "$(<)" "${Side3_Deploy}/${Package_Name}"

Back in 1984, I picked up a CX21 Video Touch Pad and decided to see if I could use it with my 8-bits. The result was a subroutine written for use with Atari Macro Assembler. Following that, I decided to wrap that into a k: device handler, such that you could read the keypad using standard CIO calls (OPEN/GET/etc). I'd recently found a hard copy printout of the original source, and have taken that and updated it to compile with ca65. The result is posted to https://github.com/bhall408/atari800-touchpad-keyboard-controller Also shared to Instagram and Twitter. Scans of the original source, as well as modern source files/makefile/etc are at the repo. Enjoy!