'RS 232 RECEIVE ONLY TERMINAL PROGRAM FOR BASIC STAMP/HD44100 LCD DISPLAY

'This simple program was developed for the 16x1 ascii LCD display from 
'TIMELINE using the 4 bit interface option, stamp set currently for 2400
'baud. Requires 1 resistor.
'Written by Jim Remington 3/93.    Email: jim@uoxray.uoregon.edu

'CONNECTIONS
'lcd pin            14  13  12  11   6   4             5    3    2    1
'port pin on stamp   7   6   5   4   3   2   1   0   gnd  gnd   +5  gnd
'function          db7 db6 db5 db4   e  rs   ? rs232 r/w   vo  vcc  gnd
'r/w on lcd is grounded, so no read functions (could use pin 1 for this).
'Stamp supplies 2 mA power to display

'variables used: b0=command byte, b1=data byte, b2 = temp

dirs = %11111100   '6 output, 2 input bits

gosub init 'initialize display - 4 bit mode with high nibble=data

'send hello string to display

for   b2 = 0 to 13
      lookup b2,("  STAMP on it!"),b1
      gosub cho
      next

b2=13  'simulate <cr> to clear at start of next line

'main loop, no check for line length. Plenty space for such options!

loop: serin 0,4,b1           '2400 baud inverted (27 K resistor interface)
      b1 = b1 & 127          'clear high bit if necc.
      if b1 = 13 then save   '<cr>, erase before next line 
      if b1 = 8 then bs      'back space, backup
      if b1 < 32 then loop   'control char
      if b2 <> 13 then nc    'don't erase line first
      b2 = 0                 'clear display and flag, last char was <cr>
      b0=0: gosub send : b0=16 : gosub send  'then output last char
nc:   gosub cho
      goto loop

'save <cr> for next char input (don't clear display immediately)
save: b2 = b1
       goto loop   

'backspace, shift cursor left, blank, shift.
bs:   b0=16 : gosub send : b0=0 : gosub send:
      b1=32 : gosub cho  'a blank
      b0=16 : gosub send : b0=0: gosub send:
      goto loop


'SUBROUTINES

init:

'set 4 bit interface and initialize, standard plus display on, cursor off

for b2 = 0 to 13
lookup b2,(48,48,48,32,32,0,0,128,0,16,0,96,0,192),b0
gosub send
next
return

send:
'output command byte b0 to port, pulse e. Note: assumes bit 2 is clear
pins = b0|8 : low 3
return

cho:
'send character in b1 to display, first top nibble then bottom
b0=b1&240+4    : gosub send  'bit 2 = 4 sets data mode
b0=16*b1&240+4 : gosub send
return