Retronetworking

h1. T-View 100

{{>toc}}

T-View 100 was a video telephone, made by Deutsche Telekom / Siemens.

@manawyrm has five of these phones, @LaForge owns two as well.

h2. External photos

{{thumbnail(DSC00422.jpg)}} {{thumbnail(DSC00423.jpg)}}

Power supply is called STN20, output DC 22.5V; 0.9A. Center positive, 5.5/2.5mm barrel jack.

The RCA connectors are (from left to right): Audio out, Video out, Video in, Audio in

h3. Mini-DIN / RS232

The Mini-DIN (8pin) connector carries a RS232 serial. It was used to connect to auxiliary devices like relay control boxes (to alert deaf people of calls), VCRs (remote control) and PCs (for firmware updates).

We have a copy of the 1.2 firmware update and the RS232 communication protocol.

RS232 pinout is given _without_  Null-Modem reversal (aka it's meant to be a male connector), reverse RXD/TXD and RTS/CTS for a female connector.

Serial settings (for debug output) seems to be 19200, 8n2.

|_.Mini-DIN|_.RS232|_.RS232 Pin|

| 1 | NC  | - |

| 2 | TXD | 3 |

| 3 | RXD | 2 |

| 4 | RTS | 7 |

| 5 | CTS | 8 |

| 6 | NC | - |

| 7 | GND | 5 |

| 8 | NC | - |

The framing and at least some commands are described in attachment:V24-Control.pdf

h3. Service menu

There is a hidden service menu. Scroll to "Service", press OK, type the number 7.

Enter passcode "3570" and press OK.

"Service" -> 8 is another hidden option for a "Factory SETUP". The passcode is 3745.

h2. Internal photos / circuit boards

h3. Video/Interfacing PCB

{{thumbnail(IMG_3633.JPG)}}

We can see here:

* Philips SAA 7111 VIP (Video Input Processor) attachment:SAA7111.pdf

* 8x83104AKAB VCP (Video Codec Processor)

** 4x ISSI IS61C1024-20J 1MBit 128Kx8 SRAM attachment:IS61C1024.pdf

** 2x Siemens HYB514171BJ-70 256Kx16 DRAM 

** AM29F040 4Mbit (512Kx8) Flash attachment:AM29F040.pdf

* Motorola XC68307FG16 attachment:XC68307.pdf

** 2x Epson SRM2B256SLMX70 32Kx8 SRAM 

** AM29F400BB-120C Flash attachment:AM29F400B.pdf (label: VCod14)

* NEC V30145-J4681-V29

* Siemens PSB7230 JADE (Joint Audio Decoder-Encoder for Videophone) V2.2 attachment:PSB7230.pdf

* NatSemi P78SF MM74HC244

* Analog Devices ADV7176KS Digital CCIR-601 YCrCb to PAL/NTSC Video Encoder attachment:ADV7176KS.pdf

h3. Telephone PCB

{{thumbnail(IMG_3644.JPG)}}

The telephone PCB has a debug header with a UART interface on it:

{{thumbnail(t-view100-debugheader.jpg)}}

*This debug header can be used to supply +5V (~100mA) to the phone board externally.*

 The phone board will work stand alone and this can be very useful for trouble shooting display issues!

{{thumbnail(behxaityrfs.jpg)}}

h3. Display/Camera PCB

{{thumbnail(IMG_3656.JPG)}}

h2. Phone disassembly

The bottom cover plate has 6 Phillips screws and is clipped together at the bottom. Use multiple guitar picks to get them free.

The plastic does not seem to be brittle (yet), some force is OK.

{{thumbnail(IMG_3647.JPG)}}

Backside of the main video / interfacing PCB is visible under the cover plate:

{{thumbnail(IMG_3631.JPG)}}

Lift the video / interfacing PCB out by pulling it straight up, it's connected via a rigid interface PCB (but not screwed down):

{{thumbnail(IMG_3634.JPG)}}

Unscrew the 7 Phillips screws attaching the plastic shield. Be careful with the speaker wires on the right, they are not detachable!

Lift the plastic shield out of the way to the right. When re-assembling, make sure the hook-mechanism and speaker are correctly in-place.

{{thumbnail(IMG_3642.JPG)}}

h2. Display/camera disassembly

Disassembling the display/camera unit is a bit tricky. You'll need a 10mm socket (and possibly socket extension)!

Start by removing the 4 screws on the connector: 

{{thumbnail(IMG_3650.JPG)}}

then remove the 3 screws in the top of the unit.

The sides of the display/camera unit are covered with round covers. They can be pulled out with a bit of force.

{{thumbnail(IMG_3652.JPG)}}

Use a 10mm socket to unscrew the nuts on both sides.

Lift the connector cover. This is tricky! Please fill in a good way to do this. The author broke 2 plastic clips by doing it:

{{thumbnail(IMG_3653.JPG)}}

Remove both bolts (and the washers). The swivel piece can now be bent inwards slightly with a bit of force to get it out.

{{thumbnail(IMG_3654.JPG)}}

Unscrew the 2 remaining screws holding the display unit together.

There are clips all around the display/camera unit. Use guitar picks again and open the display.

h2. Common faults

h3.  Faulty LCD hotbar

Symptoms: Missing (pixel) rows / columns on the (24x2) character LCD. 

Fix: Try and reheat the hotbar (~180°C) with a clean soldering iron tip and a lot of pressure

h3. Faulty HD44780 hotbar

*Note: The LCD is part of the phone's 68000 CPU bus!*

A problem with the HD44780 will keep the whole telephone from working. The phone board won't start and will wait for LCD init. The TFT will stay off, all LEDs will stay off.

Symptoms: Phone not booting at all, no display, no LEDs, completely dead. Current draw ~250mA.

Fix: Check resistance between pins on the HD44780 itself and the phone board. Usually pins like VCC, GND or some of the datapins won't have continuity or more than ~1kOhms.

Run extra wire(s) from the test points (see "Display test point pinout" below) to the 2x8 footprint on the HD44780 LCD itself. Enamelled copper wire works well for this.

You can run the phone board seperately, without the video board. Apply +5V to the debug header as shown above.

Symptoms: Garbled characters/stuck bit

Fix: HD44780 interface is connected via Hotbar as well. 

Find out which bits (D0-D7) are affected and solder wires for those bits directly to the LCD

{{thumbnail(IMG_3779.JPG)}}

{{thumbnail(Bildschirmfoto 2022-03-11 um 13.07.27.png)}}

h3. Faulty display

Symptoms: No LCD output at all

Fix: Buy a new LCD. You'll need one with HD44780 ROM code A00 charset (the Japanese/Kana charset). The 0xE1 character should be "ä" (a with Umlauts).

We couldn't find any mechanically 100% compatible model, but the NewHaven NHD-0224AZ-FSW-GBW is electrically and character set compatible. If you want to do the re-work, the following recommendations apply:

* remove the transparent plastic carrier for the old LCD module

* remove the old LCD module (just tear the flex cable from the top side of the board)

* use solder wires to connect the new LCD to vias on the PCB (see picture)

* either fix the contrast voltage to GND, or re-work the existing contrast voltage biasing circuit.  The original Siemens circuit consists of a 5V PWM feeding into a resistive divider of two 24kOhms resistors.  Replace the GND-facing resistor with a 2.2kOms (or even lower).  Play with the contrast settings (+/- buttons while receiver is on-hook) to see if you hit the right voltage range.  Adjust resistive divider as needed.

* re-work the plastic cover that is located between the two boards as needed.  You can either make more space for the LCD module by creatng a cut-out, or you can use it as-is and adjust the spacers on the "video" side.

{{thumbnail(tview-nhd-rework.jpg)}}

h4. Display test point pinout

{{thumbnail(T-View 100 Display replacement.jpg)}}

h4. Pinout hotbar/flex-cable vs. 2.54mm header

{{thumbnail(20221108_220025.jpg)}}

h4. Notes regarding adjusted resistive  divider for backlight

{{thumbnail(20221108_215856.jpg)}}

h3. Faulty capacitors

Symptoms: Crashing, low display contrast, flickering LEDs, poor video quality, mains hum on the speakers

Fix: Replace all electrolytic capacitors

Remove the old caps using the "Twist method":https://www.youtube.com/watch?v=-1S3F6_g3Sw

|_.Capacity|_.Voltage|_.Count|_.Width x Height (mm)|_.Replacement part|

|220µF|35V|8|10.31x10.31|Nichicon UCL1V221MCL6GS|

|470µF|16V|2|10.31x10.31|Nichicon UCX1C471MCL1GS|

|47µF|35V|6|8.28x8.28|Nichicon UUE1V470MNS1GS|

|220µF|10V|1|8.28x8.28|Nichicon UWG1A221MNL1GS|

|47µF|16V|3|6.60x6.60|Nichicon UCB1C470MCL1GS|

|100µF|10V|1|6.60x6.60|Nichicon UUT1A101MCL1GS|

|2.2µF|35V|2|3.33x3.33|Nichicon UWJ1H2R2MCL1GB|

|10µF|16V|1|3.33x3.33|Nichicon UUT1C100MCL1GS|

h3. Bad connections

Symptoms: Phone working, no picture, no backlight

Fix: Replug the display assembly a couple of times

h2. Bootlog (RS232 Debug)

A logfile of the external RS232 connector while booting and making a call can be found here:

https://osmocom.org/attachments/5568

h2. External Camera

There was an official external camera accessory , a Deutsche Telekom 663701-001 (re-branded Minolta EDUKCM-100)

* "FCC report":https://fcc.report/FCC-ID/EDUKCM-100

h2. Prototype

@manawyrm stumbled across a T-View prototype:

{{thumbnail(DSC00021.JPG)}} {{thumbnail(DSC00022.JPG)}}  

{{thumbnail(DSC00023.JPG)}} {{thumbnail(DSC00024.JPG)}}  

{{thumbnail(DSC00026.JPG)}} {{thumbnail(DSC00027.JPG)}}  

Noticeable differences include:

- Green LEDs (instead of Red LEDs)

- White printing on the connectors (instead of embossed text in the plastic)

- Handset has a magenta T-symbol, instead of the white T-symbol

- HD44780 display is connected via jumper wires (instead of hot bar flat-flex cables)

- ProfiTel70 / Phone board is powered only by S0 bus voltage, not through DC in

- 0.1" pin header populated on the phone board

- handwritten label for firmware flash IC on the phone board

- PLCC socket for firmware flash IC on the video board

- VCP is still manufactured by IIT, later split off into 8x8

- bad mechanical fit (RJ45 latch cannot be accessed without tools, recessed too deep)

- CNC toolmarks are visible in plastic housing (CNC aluminium soft mold was probably used for injection molding)

- generic FRIWO FW 7324/3 24V power supply, instead of the 22.5V STN20 PSU

The broken display was replaced with the new Newhaven type (see above):

{{thumbnail(IMG_6017.JPG)}} {{thumbnail(cxyjhtglofw.jpg)}}

VCP (version 4014) dump: https://osmocom.org/attachments/5688

h2. Firmware

There are four known firmware versions:

|_.Version|_.Release Date|_.Telefon|_.Codec|_.VCP|_.Jade|

|V1.0|July 1998|?|?|?|?|

|V1.1|?|33|14|4014|2.2|

|V1.2|December 1998|43|20|4025|2.2|

|V1.3|?|47PT|23T|4025|2.2|

Telefon/Codec/VCP/Jade firmware versions can be checked in the service menu (see above).

The firmware consists actually of different images for different processors on the unit.

|_.Filename|_.Format|_.Purpose|

|vcvcp.bin|binary|presumably for the video codec/processor|

|vsetrel.abs|srec|for the VSet (telephone) board, derived from ProfiTel70|

|vcodrel.abs|srec|contains strings related to H.261, H.221 and VCP|

The Firmware update utility running on the PC side is called Fload68k.exe "M68k Flash-Loader V 3.31 (C) 1997 Orsys GmbH" and it talks about three parts:

* "Talkset" (abs format, programmed via SPI or "RS232 direct")

* "VCODEC" (abs format, programmed via via "RS232 direct")

* "VCP" (bin format, separate programming mode "VCP")

h2. External Links

* https://www.eetimes.com/88-video-chip-powers-deutsche-telekom-videophone-dt-orders-250000-isdnvideophones-from-siemens-pn/

* https://www.teltarif.de/arch/2001/kw01/s3986.html

* https://www.wissenschaft.de/allgemein/bildtelefon-t-view-100-auge-in-auge/