Sinclair ZX80 / ZX81 / Z88 Forums

Charlie,

I used a meter and found +5v, Gnd on the ZXPand+ idc10 cable. I'm using a Parallax 2x16 Serial LCD with it having 4 modes (test, 2400, 9600, 19200).The LCD has pins for 5vdc, God and RX. I connected the i'dc 10 connectors pin 9 TX to the LCD RX as well as 5vdc and gnd pins.

When the LCD is set to 19200 via the mode switch on the LCD, I see some characters like GV on the top row and v5 or something on the second row upon power up of ZXPand+ with LCD attached. At 2400 and 9600 settings the LCD screen is blank like I would expect. I'm receiving another Parallax 4x20 serial LCD in the mail today which should operate identically.
How do I send a HIGH out from the ZXPand+ TX ?

I'm having a little success in seeing characters but at the wrong position. I have to send +5vdc (or a HIGH) command to the ZXPand+ Serial TX pin to initialize the LCD RX pin. Then I have to send the LCD Hex commands (or decimal 0-255) to tell the LCD where the cursor should be, turn LCD backlight off/on, etc.

Is there anyway to send the ZXPand+ serial TX pin Hex or Decimal commands besides text characters?

i was under the impression you could put arbitrary bytes in memory somewhere ( say a rem statement ) and issue the connamd

ZXPAND "PUT SER *16514 32"

which would send 32 bytes stored in a line 1 rem statment...

least thats how i understand it..

regards Andy

p.s just a thought for SirMorris what about... PUT HEX 001122334455...

Thanks Andy. I will try that. Not at home at the moment. Bytes in decimal is fine so hex is nice but let's see if decimal works first.

All,

I finally got it working meaning interfacing a Parallax Serial LCD to ZXPand+ on the serial port (IDC 10).

This is showing a 2x16 Parallax LCD display.

I also have a bigger Parallax 4x20 LCD display that arrived today and the code works the same.

Tim

Great stuff, glad you got it working,

Regards andy

The only significant issue is that there needs to be a way to send 5vdc (High) and Gnd (Low) to the TX pin to initialize the LCD. The only work around so far is to run the program twice,

Looking good! I've been AFK until now and loads seems to have happened in the time being

Is there a time constraint on the high/low protocol for initialising the interface? Would sending a value with one bit set do the trick? like 00000010 binary.

There is no time constraint but trying to have something interesting for the vintage computer show next month. I will start focusing on the Atari joystick port testing next to understand how it works with ZXPand+ and then incorporate both joystick and LCD into a text demo.

It appears there is about 4.8vdc on TX when ZXPand is first turned on but it causes some strange characters and tones (LCD has a piezospeaker fir music notes). I would think this should cause it to initialize but there is something I'm missing or not understanding.

I tried using ZXPAND "OPE SER *16514 1". Where the REM Statement had a value for 255 for a HIGH but no go.