eMBee BASIC

Now you can turn an Altoids tin and an Arduino into an 80's pocket computer! More info on the eMBee ONE pocket computer at the project's home on Hackaday.io: https://hackaday.io/project/177180-embee-one-pocket-computer

Based on Robin Edwards' excellent Arduino BASIC, this is the software for a complete pocket computer, using an Arduino Nano (or clone), a CardKB I2C keyboard, and SPI OLED screen. The BASIC supports almost all the usual features, with float and string variables, multi-dimensional arrays, FOR-NEXT, GOSUB-RETURN, etc. Saving and loading from internal and external EEPROM is supported, as well as auto-running a program on power-up. You can also read and write from the analog and digital pins.

There's about 1k of RAM available for your BASIC programs and variables, so its roughly equivalent to a Sinclair ZX81. The other 1k of RAM (on a Nano) is used for the keyboard and screen buffers, with a small bit of room left for the CPU stack. That works out quite well, since there's a 1k EEPROM on the Nano so if your program fits in the basic environment, it will fit when saved to EEPROM!

Prerequisites

1: An Arduino with at least 2k of RAM. i.e. Nano/UNO/Duemilanove/etc. It should also work on the MEGA but is untested. I think the sketch is too big for the Leonardo, since it looks like the bootloader uses more RAM on this model.

2: A CardKB keyboard

3: An SSD1306 based OLED Screen connected using SPI. See e.g. http://www.adafruit.com/product/938. I think it should also work fine with the 128x32 version - you'll just need to change a couple of defines.

4: An Altoids tin to make it a truly portable device. I used an Adafruit PowerBoost 500 Basic to connect the Nano to 2 x AAA batteries for power.

5: (Optional) A Piezoelectric buzzer for keyboard clicks and other sounds.

6: (Optional) A external EEPROM (e.g. 24LC256 giving 32KB storage) lets you save more than one file. You can pick these up for about £2/$2 on ebay.

Getting Started

1: Download the zip file, unpack and copy the folder to your arduino sketches directory.

2: Go to Manage Libraries, search for 'Digital Infrared Temperature Sensor MLX90615' and install it (in order to get 'I2CMaster')

3: Install the SSD1306ASCII library (updated by Robin Edwards for speed - included in package)

4: Check your wiring corresponds to the pins in the comments/defines at the top of the eMBee_BASIC file.

BASIC Language

Variables names can be up to 8 alphanumeric characters but start with a letter e.g. a, bob32 String variable names must end in $ e.g. a$, bob32$ Case is ignored (for all identifiers). BOB32 is the same as Bob32. print is the same as PRINT

Array variables are independent from normal variables. So you can use both:

LET a = 5
DIM a(10)

There is no ambiguity, since a on its own refers to the simple variable 'a', and a(n) referes to an element of the 'a' array.

Arithmetic operators: + - * / MOD
Comparisons: <> (not equals) > >= < <=
Logical: AND, OR, NOT

Expressions can be numerical e.g. 5*(3+2), or string "Hello "+"world". Only the addition operator is supported on strings (plus the functions below).

Commands

PRINT <expr>;<expr>... e.g. PRINT "A=";a
LET variable = <expr> e.g. LET A$="Hello".
variable = <expr> e.g. A=5
LIST [start],[end] e.g. LIST or LIST 10,100
RUN [lineNumber]
GOTO lineNumber
REM <comment> e.g. REM ** My Program ***
STOP
CONT (continue from a STOP)
INPUT variable e.g. INPUT a$ or INPUT a(5,3)
IF <expr> THEN cmd e.g. IF a>10 THEN a = 0: GOTO 20
FOR variable = start TO end STEP step
NEXT variable
NEW
GOSUB lineNumber
RETURN
DIM variable(n1,n2...)
CLS
PAUSE milliseconds
POS x,y sets the cursor
PIN pinNum, value (0 = low, non-zero = high)
PINMODE pinNum, mode ( 0 = input, 1 = output)
LOAD (from internal EEPROM)
SAVE (to internal EEPROM) e.g. use SAVE + to set auto-run on boot flag
LOAD "filename", SAVE "filename, DIR, DELETE "filename" if using with external EEPROM.

"Pseudo-identifiers"

INKEY$ - returns (and eats) the last key pressed buffer (non-blocking). e.g. PRINT INKEY$
RND - random number betweeen 0 and 1. e.g. LET a = RND

Functions

LEN(string) e.g. PRINT LEN("Hello") -> 5
VAL(string) e.g. PRINT VAL("1+2")
INT(number) e.g. INT(1.5)-> 1
STR$(number) e.g. STR$(2) -> "2"
LEFT$(string,n)
RIGHT$(string,n)
MID$(string,start,n)
PINREAD(pin) - see Arduino digitalRead()
ANALOGRD(pin) - see Arduino analogRead()

Still to come

ABS(number) e.g. ABS(-6)-> 6
BEEP (to drive the buzzer on pin 5)
CHR$ (converting ASCII numbers to characters)
User defined graphics - altering the built in characters for rudimentary text-based graphics