Add test assembler code to match Go and Node.js code

Firmware/assemble_test.sh

@@ -0,0 +1,3 @@
+#!/bin/sh
+ca65 test.asm
+ld65 test.o -o test.bin -t none

Firmware/test.asm

@@ -0,0 +1,11 @@
+	ldx	#$50	;slot 5 for this test
+start:	lda	#$80	;set read flag low (ready to read)
+	sta	$c08d,x	;bit 1 low for writing values
+waitwl:	lda	$c08e,x	;bit 0 low for reading values
+	bmi	waitwl	;wait for write flag low	
+	jsr	$fde3	;print nibble of data
+	lda 	#$c0	;set read flag high (done reading)
+	sta	$c08d,x
+waitwh:	lda	$c08e,x
+	bpl	waitwh	;wait for write flag high
+	bmi	start	;go around againg for next nibble