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)

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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
    },