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ICE40 based passive tap

In 12/2019, tnt implemented a bi-directional passive E1 tap device that samples the entire raw 2MBps data stream in both directions.

This is useful in situations where the E1 line is not used channelized, i.e. not with individual 64kBps timeslots, such as in frame relay or 'wideband ISDN' (B-ISDN) use cases, where osmo-e1-recorder and re-combining 64k slots in the capture has not always been successful.

Contrary to the "normal" (end-of-line) ICE40_E1_USB_interface, this approach uses actual E1 LIU (Line Interface Unit) hardware in order to use their built-in equalizer and additional gain for passive tapping of long-haul E1 lines.

The setup conceptually looks like this:

Bitstream / Firmware / Host PC Software

The firmware can be found in the e1-recorder branch of the ice40-playground git repository

Pictures

APU2 assembly with 2x e1-xcvr and iCEpick

APU2 assembly with 2x e1-xcvr and iCEpick

APU2 assembly with 2x e1 xcvr interconnected with e1tap

APU2 assembly interconnected with tap

Two E1 XCVR with LOS (Los Of Signal) ON

e1xcvr with LOS LED ON

Two E1 XCVR with LOS (Los Of Signal) OFF

e1xcvr with LOS LED OFF

iCEpick with LED cyan (all OK)

iCEpick with LED cyan (all OK)

APU2 LEDs (labelled in German)

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