Introducing Bitlash

Bitlash is an open source interpreted language shell for the Arduino serial port. It runs on the Arduino and interprets commands that you type in a terminal window or send programmatically:

Bitlash is a development and prototyping tool for those situations where you need to bang some bits on the Arduino but writing a sketch in C is premature. The Bitlash command language is very similar to Arduino C and includes a large repertiore of the familiar Arduino C functions so you can hack your hardware from the serial command line or even over the internet via telnet.

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.nolist			; We don't want to actually include defs in our listing file.
.include "m168def.inc"	; m168def.inc defines all the pins on the Mega168 so we can
			; use them by their names rather than addresses (not fun).

.list			; We DO want to include the following code in our listing ;D

	rjmp	main 	; You usually place these two lines after all your
main:			; directives. They make sure that resets work correctly.

	ldi	r16,0xFF ; LoaD Immediate. This sets r16 = 0xFF (255)
	out	DDRB,r16 ; Out writes to SRAM, which is one way of accessing
			 ; pins. DDRB controls PORTB's in/out state.

	ldi	r16,0x00 ; r16 is where we'll store current LED state
			 ; 0x00 means all off. This is preserved over loops.

; LEDblink.asm - M. Covington 2006 
; For ATtiny13. 
; Blinks the LEDs attached to PB0 and PB1. 

.include "tn13def.inc" 

.def temp = R16 
.def temp1 = R17 
.def temp2 = R18 
.def mask = R19 

start: ldi temp,0b00000010
       out PORTB,temp ; initialize port B 
       ser mask 
       out DDRB,mask ; port B all outputs 
blink: 
       ; Delay 0.1 sec (1.2 MHz) 
       ldi temp1,200 ; outer loop count 
L1:    ldi temp2,199 ; inner loop count 
L2:    dec temp2 
       brne L2 
       dec temp1 
       brne L1 
       ; Toggle PB0 and PB1 
       ldi mask,0b00000011 
       eor temp,mask 
       out PORTB,temp 

       rjmp blink 
; End of program

First, we configure pin 13 for output by setting a bit in Data Direction Register B. Then we turn pin 13 by setting its bit in PORTB. Then we delay 500 milliseconds by marking the current value of timer0, converted into milliseconds, and letting the counter be incremented repeatedly at each clock cycle and overflowed into ever larger holders until the new value of timer0 represents an elapsed time of 500ms. Next we set the bit for pin 13 in PORTB low to turn the LED off. We do the delay dance again and we're home.

This is the first in a series of articles about generating sound with an Arduino. The goals are to generate good quality sound which can be used to play simple tones, stored music, sampled sound, and even act as a MIDI synthesizer. I will cover the basic design, including code and hardware that anyone can use to add sound to Arduino microcontroller projects.

The first step is to look what has already been done. We want to explore many possible options for sound generation and resolve which is best for given situations. I hope to spark some discussion so please comment with information links, advice, suggestions and general opinions.