[[hardware]]
== icE1usb Hardware

The icE1usb Hardware consists of a single circuit board (in an optional
enclosure).

It's main building blocks are:

* an iCE40 FPGA
* Two E1 line interface (transformers, biasing networks and ESD protection) footnote:[Only one E1 line supported by firmware so far]
* a GPS receiver module with 1PPS output to the FPGA footnote:[GPS-DO supported by firmware yet]

=== Schematics

As icE1usb is an OSHW (Open Source Hardware) project, the full schematics
and design files are publicly available.

The design files in KiCAD formwa are available at https://git.osmocom.org/osmo-e1-hardware/tree/hardware/icE1usb

PDF rendered schematics are available at https://git.osmocom.org/osmo-e1-hardware/plain/hardware/icE1usb/r1.0/icE1usb.pdf

=== Connectors

==== X5A and X5B: E1 Interface Connectors

On one side of the PCB there are two RJ45 connectors next to each other.

Those are the two E1 line interfaces.  The interfaces are of symmetric
120 Ohms type.

Assuming the board is oriented with the tab of the RJ45 connectors facing
up:

* Interface 0 is on the right side
* Interface 1 is on the left side (next to the button)

The pin-out of the connectors can be swapped between TE and NT mode using
the J4 and J5 jumper blocks on the circuit board.

A GSM BTS typically implements TE pin-out, while the icE1usb should then
use NT mode pin-out if no cross-over cable is used.

.Pin-out of RJ45 E1 connectors
[options="header"]
|===
| Pin | Function (TE) | Function (NT Mode)
| 1   | Rx            | Tx
| 2   | Rx            | Tx
| 3   | not used      | not used
| 4   | Tx            | Rx
| 5   | Tx            | Rx
| 7   | not used      | not used
| 8   | not used      | not used
|===

NOTE: E1 cables use RJ45 like Ethernet, but Ethernet cables have a
different pin-out.  Particularly, you cannot use an Ethernet cross-over
cable as an E1 cross-over!

==== X4: USB Connector

The USB connector is a USB Type C connector.   However, it only carries
USB 1.1 full-speed signals.  5V DC power is also sourced from this
connector.

==== X2: Serial Console Connector

The serial console is used for development and debugging.  It uses an
Osmocom-style 2.5mm stereo TRS jack.

The serial console uses 3.3V CMOS logic levels

The serial console uses a rate of 1000000 bps.

The pin-out is as follows:

* Tip: Tx output from PC (Rx input of icE1usb)
* Ring: Rx input of PC (Tx output of icE1usb)
* Shield: GND

A compatible cable can be sourced from the sysmocom web-shop at
http://shop.sysmocom.de/.

==== X1: GPS Antenna Connector

The GPS antenna connector is a female SMA connector.

You can connect most standard active GPS antennas with built-in LNA.

icE1us provide phantom voltage.

The use of a GPS antenna is only required when you need a high precision
clock reference for the 2.048 MHz E1 bit clock, e.g. to provide a clock
reference to a cellular base station on the A-bis interface.

==== X3: GPIO / Extension Connector

This is a RJ45 connector adjacent to the USB connector.

It is currently unused and reserved for future use.


[[hw-pushbutton]]
=== Pushbutton

This is a push-button next to the _E1 interface '1'_.   It is recessed
to protect against accidental use.   You will need to use a paper clip,
pen tip or other similar object to push it.

The button can be used to force booting into the DFU loader in order to
recover from a broken firmware installation.


=== Multi-Color LED

Above the USB-C connector, there is a multi-color RGB LED.

This LED is used by the firmware to indicate a variety of status
information.  Pleas see the firmware documentation in <<firmware>>.