Coinvox 22

Project: Coinvox 22
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Description	Get an old payphone to work again
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Coinvox 22 looks complete..

..but is stipped empty :(

Keypad I²C interfaced

synopsis

I got myself a Coinvox 22, reasonably cheap. The downside is: the inner workings have been stripped out, so it's just a metal box with keypad and display, a handset with hook-switch and a small transformer.

No coin mech, no ringer, no phone.

inside

handset / hook-switch

The handset is tested and is in good shape. It is connected to a PCB.

• 2 different reed switches
• 4 coils
• 2 3-pin SOT 23 (SMD) diodes(?) (D1, D2: A7 P 45)

J1 Handset connector. Layout is (male) PCB connector side.

|o  spk
|o| mic -
|o| mic +
|o  spk

J2 Connector which ought to go into the main PCB. Layout is (female) connector side.

mic+ 2 |oo| 1 spk
 spk 4 |oo| 3 mic-
 NC1 6 |oo |5 n/c
 NO1 8 |oo| 7 P1
  P2 10|oo| 9 NO2

Note: SW1 switches first (about 2mm) when hanging up, probably used for muting the microphone.

keypad / display

• IC2: PCF8576T (Universal LCD driver for low multiplex rates, I²C address 38h)
• IC3: PCF8574T (Remote 8-bit I/O expander for I²C-bus with interrupt)

  Addresses tied to ground; address 20h.

J Display/keypad connector. Layout is (female) connector side. Int needs pullup, and print is found working at 5V.

SCL 2 |oo| 1 SDA
    4 |oo| 3 
GND 6 |oo |5 VCC
    8 |oo| 7 
Int 10|oo| 9 

Display

• 8 × 14 segment display, characters are filled from the right
• 52 pins with the only the outer 9 connected (36)
• uses 4 back-plane mode (all corners)

Segment layout. Note that bit 3 is not used, which aligns the characters to 16 bit.

       15
    _________ 
 
  | \11 |   / |
 2|  \  |7 /6 |14
  |   \ | /   |
 10----  -----5
  |   / | \   |
 1|  /  |  \4 |13
  | /9  |8  \ |
   __________
        0       o12
 bit 3: not used

Keypad

	col1 (P7)	col2 (P4)	col3 (P5)	col4 (P6)
row1 (P1)	n/c	1	2	3
row2 (P1)	n/c	4	5	6
row3 (P2)	N	7	8	9
row4 (P3)	Vol	*	0	#

To read out the keypad (on interrupt pullup), set one row low and read the column nibble. Repeat for each row. Low bit means key pressed.

Text on the PCB:

LGCO-CH BTC15 DESKII

4 431 4223 0 22

Text found on some stickers:

Landis & GYR

412197580 A

Version.mec: A

Date fab : 02/95

plans

• upload reference material of the Coinvox phones (hacktic, 't klaphek, telephone museums ([1][2][3][4][5][6][7])
• experiment with my (front fed) coin mech (or look for a top fed mech that fits)
• experiment with a cisco phone (see if I can use the softkeys and the AUX port to read quarters or just Euro coins
• connect an ATA to an old phone

todo

• upload display/keypad initialization commands
• write a library for the display/keypad (fix the hacky code)
• see if the serial protocol of a Cisco phone is of any use
• find an old mechanical phone bell
• identify ICs, obtain datasheet, determine pinouts Success!