News @ Suspect Devices

Category: Raspberry Pi

  • Raspberry pi to vt320 interface..

    Raspberry pi to vt320 interface..

    My holiday project.

    I am really disliking the new wordpress editor. It wasn’t broken. May move this site to markdown and hugo.

  • Introducing my latest rathole: PiTerm1986

    This is a snapshot of the current readme: Updates and current progress are on its github page: https://github.com/feurig/PiTerm1986

    GOAL: Convert 80s style user interface ( 8031 based ADP Product: chicklet keyboard and 2×20 lcd ) to pi zero based terminal using i2c based io expanders.

    Looking under the keyboard membrane and tracing the connectors we can get the following key map under a 4×12 array (16 pins).

       0123456789 10  11
   --------------------
0) *# ZXCVBNM/    <STOP>
1) -LASDFGHJK<N/C><ENTER>
2) 0912345678<BS> <START>
3) POQWERTYUI<CAN><DIAL>
    *#ZXCVBNM/STOP
    –LASDFGHJKN/CENTER
    0912345678<—-START
    POQWERTYUICANCELDIAL

    Keyboard

    For this we look at the AW9523 GPIO expander with 16 pins of io.

    LCD/VFD

    Since the LCD is a 5v circuit requiring either 8 or 12 pins we look at the Microchip MCP23017 on the Adafruit GPIO Expander Bonnet which we can wire either using both ports or one port in nibble mode.

    Via : https://protostack.com.au/2010/03/character-lcd-displays-part-1/

    Attaching Both Boards to the Raspberry pi.

    root@somepi1:/home/feurig# i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: 20 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- 58 -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --

    Assembly and layout.

    After putting the board in the box I realized that the grey paint was conductive and that I almost let the smoke out of the pi zero. (you could smell it). So I went out and found a piece of plastic from a previous project. 

    And then I was like OH SHIT I have Noritake 2×24 VFD thats a close fit..

    So there’s a circuitpython library for an mcp23017 connected to an lcd. Wiring it up according to the above schematic lets us write away

    root@somepi1:/home/feurig# pip3 install adafruit-circuitpython-charlcd
...
root@somepi1:/home/feurig# python3
Type "help", "copyright", "credits" or "license" for more information.
>>> import board
>>> import busio
>>> import adafruit_character_lcd.character_lcd_rgb_i2c as character_lcd
>>> lcd_columns = 24
>>> lcd_rows = 2
>>> i2c = busio.I2C(board.SCL, board.SDA)
>>> lcd = character_lcd.Character_LCD_RGB_I2C(i2c, lcd_columns, lcd_rows)
>>> lcd.message = "Hello\nPiTerm1986"
>>> lcd.clear()
>>> lcd.message = "PiTerm 1986 v0.0\nOk >"
>>>

    I am not thrilled about the way its wired but whatever.

    References