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Example_SEU M_OeAGT

Rolf Obrecht edited this page Jul 31, 2024 · 2 revisions

Example with SEU-M-board with Raspberry Pi in an Austrian AGT for TW39

SEU-M-board

For details of the SEU-M-board see MicroTelex-wiki

The Austrian AGT (Ö-AGT)

An AGT is a converter to adapt a historic teletype with current loop (TW39) to a frequency shift keying station (ED1000).

The name 'AGT' stands for German "Anschaltgerät"

The device contains of

  • regulated power supply (+60V, -60V and +12V)
  • converter electronic H-bridge (RX, TX)
  • connector for a SES-B-card (V.21 transceiver)
  • ADo8 connector for teletype current loop
  • power connector (Shuko) for teletype power (no fuse, no switch)
  • ADo8 cable to station
  • power cable to 230V wall outlet
  • housing

With SEU-M-board

Simply insert the SEU-M card with a Raspberry Pi (Zero (W), 1B, 2B 3) and piTelex image into the AGT and you already have a cheap alternative to participate in the i-Telex network.

The user in front of the FS will not notice any difference whether the LO2000 is operated with i-Telex or piTelex or with the SEU-M card inserted.

The SEU-M card and the Raspberry are supplied with power via the LO2000.

Inside the Ö-AGT

A Transformer provides the power for 2 independent and isolated power supplies on the same PCB.

The +60V and -60V part has a common ground. Over the H-bridge the supply provides the 120V for the TW39 current loop. The voltage is regulated by darlington transistors and Z-diodes.

The 12V part powers the data side (TX, RX) and the SEU-B device. The voltage is regulated by a LM7812 regulator.

For powering a bigger uC (like RPi) it is recommended to use the voltage before the LM7812 regulator (20V) to prevent overheating the LM7812.

Note: The 60V and 12V parts are galvanic isolated.

IMPORTANT! The 0V-power-level is connected to earth (PE). Using an oscilloscope can damage the circuit!

Power consumptions

  • Ö-AGT (without all): 3,8W
  • Ö-AGT + SEU-M + RPi1 (Ruhemodus): 7,5W
  • Ö-AGT + SEU-M + RPi1 (Schreibmodus): 10,0W
  • Ö-AGT + SEU-M + RPiZeroW (Ruhemodus): 6,2W
  • Ö-AGT + SEU-M + RPiZeroW (Schreibmodus): 11,7W
  • Ö-AGT + SEU-M + RPi2B (Ruhemodus): 6,0W
  • Ö-AGT + SEU-M + RPi2B (Schreibmodus): 11,0W

Optional power saving circuit

If the Ö-AGT is to be expanded to include a power-saving circuit, only a solid-state relay (SSR) and a fuse are required. The control is done by the piTelex software.

Connectors on the Ö-AGT board

Connector AGT-X1

Pin Cable Color Name Comment
1 wt in b connected to X2-1
2 br in a connected to X2-2
3 ye out b connected to ADo8 4
4 gn out a connected to ADo8 1
5 nc
6 12V 12V
7 GND GND

Note: No marking for this connector on the board. Numbering is assumed

Connector AGT-X2

Pin Cable Color SES-B Pin SES-B Name Comment
1 wt 3 b connected to X1-1
2 br 2 a connected to X1-2
3 gn 4 T0 GND
4 ye 9 T+ 12V
5 gy 11 T- GND
6 rs 12 Dab RX - from AGT to uC, 12V level
7 bl 15 Dan TX - from uC to AGT, 12V level
8 rd 17 B+ 12V
9 bk 19 B0 GND

Note: No marking for this connector on the board. Numbering is assumed

Connector SES-B-card

The Ö-AGT and the SES-cards uses a connector with name "DIN41617".

Ö-AGT has a 31-pin female connector. The SES-cards has an 21-pin male connector with common pin 1.

For this project a 13-pol male connection (starting at pin 9) provides all necessary signal for controlling the Ö-AGT.

Pin Cable Color SEU Name Comment
2 br a connected to ADo8-cable pin 4
3 wt b connected to ADo8-cable pin 1
4 gn T0 GND
9 ye +T 12V
11 gy -T GND
12 rs Dab AGT_RX - from AGT to uC (pullup resistor of 5.6kOhm to 12V)
15 bl Dan AGT_TX - from uC to AGT (pullup resistor of ?kOhm to 12V)
17 rd +B 12V
19 bk B0 GND

Note: The original SES-B-card uses 21 of the 31 pins

Additional on SEU-M-board

Additional to the SES-B pinout internal signals are available on the 31-pin connector.

The pins above 21 are used on the SEU-M-board to provide additional signals (VDD, 5V, I2C, power relay, aus relay).

Pin Name Comment
24 I2C SCL
25 I2C SDA
26 +5V 5V out
27 GND
28 VDD 12V out
29 AUX-Relay for extern relay/SSR connected to +5V or VDD
30 POW-Relay for extern relay/SSR connected to +5V or VDD
31 9...24V Input for DC/DC converter (typical in Ö-AGT)

Software

See TW39 Raspberry Pi

Configuration (telex.json)

    # TW39-teletype using an Austrian AGT (OeAGT) with SEU-M-card as controller
    "RPiTTY_SEU-M_Oe-AGT": {
      "type": "RPiTTY",
      "enable": true,
      "mode": "AGT",
      "pin_txd": 17,
      "pin_rxd": 27,
      "pin_relay": 22,
      "inv_relay": true,
      "pin_power": 9,
      "inv_power": false,
      "pin_number_switch": 10,
      "inv_number_switch": true,
      "baudrate": 50,
      "coding": 0,   # 0=ITA2
      "loopback": false,
      "WB_pulse_length": 60
    },
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