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avrbasic

An interactive BASIC interpreter for the ATmega328p.

Re-live your TRS-80 memories with your ATmega. Maybe.

image of it running

image of it running more

I'll do a hardware diagram and stuff like that soon.

Parts list:

  • ATmega328p
  • ST7920, headers, lots of pin–plug header cables
  • the keyboard in /keyboard, or anything else that uses UART
  • Whatever you use to program and power your AVR

Language description:

  • Integers and strings are supported.
    • Integers are any string of numbers from -32768 to 32767.
    • Strings are any set of characters within double-quotes. No escaping is permitted.
  • Variables are identified by labels ending in % (integers) or $ (strings).
    • Only the first two letters are significant.
    • XY% and XYZ% are the same (integer) variable.
    • XY$ is a (distinct) string variable.
  • Expressions are numbers, strings, labels (variable references), in conjunction with any combination of +, -, *, /, = (equality test).
    • Usual binding order applies. Override with parentheses.
    • Numbers support all operators. Strings only support + and =.
    • Testing equality results in the number 1 (true) or 0 (false) regardless of the operand types.
  • The following statements are supported:
    • LET label = expr — assign a variable
    • PRINT expr[, expr …] — output any expression
    • INPUT ["MESSAGE",] label — get user input
    • IF expr THEN — start executing code only if expr is a non-zero integer or non-empty string
    • ELSEIF expr THEN — during an IF, if a previous block has not executed, start executing code if expr evaluates as above
    • ELSE — during an IF/ELSEIF, if no previous block has executed, start executing code
    • END IF — end an IF/ELSEIF
    • [number] stmt — store program code at the given line number
    • GOTO number — transfer program control to given line during RUN
    • RUN — run stored program
    • LIST — list stored program code
    • CLEAR – erase stored program (use if pheap runs out)