Using ZBasic

There are essentially three steps to creating a ZBasic application and these steps are reflected in the diagram below and are as follows:

• Write and compile program
• Download program to EEPROM
• Test program and repeat

ZBasic comes with a modern IDE that allows the programmer to produce a multi-file project. The IDE has a built-in editor with cut and paste, undo and program completion not found in the BasicX editor. The IDE also acts as a front-end to the ZBasic compiler, downloader and COM port monitor. The ZBasic compiler is of a modern design that incorporates many advanced features including control over optimizations. The compiler can also detect potential coding problems such as when variables are used before they have been initialized, unused parameters, unset function return values, and unreachable code.

The compiler can be run in a stand-alone mode or more usually from the IDE. When compiling a ZBasic program in the IDE any errors are listed and the line in question is highlighted. The outputs from a successful compilation include a map file, optionally a listing file and a ZXB file that contains the equivalent code in the ZBasic virtual machine language.

The next step is to download the program to the 32K bytes EEPROM memory connected to the ATmega32 Serial Peripheral Interface (SPI) bus. The IDE or a stand-alone downloader on the PC initiates the download process and the ZBasic runtime takes care of communications with the host PC and downloads the program into the EEPROM memory. At this point the program is ready to be run by the virtual machine inside the flash memory of the AVR chip.

The third step is that the virtual machine resets itself and after initialization loads the first few bytes of the program from EEPROM memory. The virtual machine interpreter decodes the instruction and executes it. Further program instruction bytes or program data are loaded from EEPROM as required. A COM port monitor on the PC can be used to send and receive data to the ZBasic runtime via the AVR USART. At this point the user is either testing or running the program which is interacting with the outside world through the built-in I/O facilities of the ATmega32 chip.