V.24 Level Shifter Board

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This is a page about the v.24 level converter I made to be fully drop in replacement for the OEM board.

Features

  • Full OEM Compatibility - This will work in place of the OEM board
    • Includes a relay so that the station can originate clock _OR_ be clocked by DCE.
  • Simple design - Affordable and easy to assemble, only one IC
  • The following can be done via dip switch at the RS232 level
    • CD asserted and tied to MARK or SPACE
    • Tie TXCLK and RXCLK together - this allows a station to connect to another which is set to not send TX clock
    • Tie CTS and RTS together - needed in some cases for certain v24 to DCE connections
  • Built in cross over port to connect two stations directly without needing a crossover adapter.
  • Internally ESD (15kv) protected design - meets or exceeds the OEM v.24 daughter card or other designs based on the MC145406
  • Fits in the front or back ports of the Wireline board without contacting or putting pressure on other compntes on the wireline board.
  • Builtin v.24 network tap for debugging (both RJ-45's are connected to the lines.)
  • Not a Graham Cracker.

Tested Config

  • Quantar/Quantro base station
  • PDR3500 Base station
  • AstroTAC 3000 Comparator [1]

Tested with TRN7477, TRN7667, CLN6955, CLN6956 and CLN7343 wireline boards.

notes

The Astero-Tac 3000 needs CD active to put the port active.

Background info

https://www.ti.com/lit/an/slla544/slla544.pdf

https://www.analog.com/en/resources/technical-articles/fundamentals-of-rs232-serial-communications.html

https://www.analog.com/en/products/max3185.html

https://www.analog.com/media/en/technical-documentation/data-sheets/MAX3185.pdf

Maxim datasheet has the pin-out wrong on page 5 for the T3IN and T1IN lines. This is being resolved, but T3 is 13 and T1 is 16 with the chips i have. This also matches the SN75185 chip that it's designed as drop in replacement for.

good:

https://electronics.stackexchange.com/a/649122

https://www.ti.com/lit/ds/symlink/tl145406.pdf

Revisions

2024-05-12

Discovered the MAX3185 datasheet has pins 13 and 16 swapped on it. All the CAD models have the same swap. After cutting and fixing this, the board works as expected.

Will need to do a respin once Maxim/Analog Devices gets back to me.

2024-05-01

PCB needs to be respun IO ports are reversed on the IO lines of the level converter.

Change the switch to use RS232 levels vs 5v TTL levels for 2-4.

  1. ↑ this needs the CD line asserted
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