Golay Encoder (`golay_encoder_us_ul`)

Takes 12 bit input data and encodes it into a Golay codeword.

Tested platforms include xsim, e31x.

Design

A Golay code is an error correcting code used for forward error correction in digital communications.

Given a unsigned short, the Golay encoder component looks at the 12 LSB bits and encodes it into a Golay codeword, placed in the LSB bits, using a Golay encoding algorithm (24 bit wide codeword if the extended Golay code is implemented or 23 bit wide codeword if the perfect Golay code is implemented).

A block diagram representation of Golay [24,12,8] is given in Figure 260:.

Figure 260: Block diagram outlining Golay [24,12,8].

Interface

<?xml version="1.0"?>
<!-- This file is protected by Copyright. Please refer to the COPYRIGHT file
     distributed with this source distribution.

     This file is part of OpenCPI <http://www.opencpi.org>

     OpenCPI is free software: you can redistribute it and/or modify it under
     the terms of the GNU Lesser General Public License as published by the Free
     Software Foundation, either version 3 of the License, or (at your option)
     any later version.

     OpenCPI is distributed in the hope that it will be useful, but WITHOUT ANY
     WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
     FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
     more details.

     You should have received a copy of the GNU Lesser General Public License
     along with this program. If not, see <http://www.gnu.org/licenses/>. -->
<componentspec>
  <port name="input" producer="false" protocol="ushort_timed_sample-prot"/>
  <port name="output" producer="true" protocol="ulong_timed_sample-prot"/>
</componentspec>

Ports

Inputs:

input: Primary input samples port.
- Protocol: ushort_timed_sample-prot
- Optional: False

Outputs:

output: Primary output samples port.
- Protocol: ulong_timed_sample-prot
- Optional: False

Opcode Handling

The Golay encoder encodes data with sample opcodes only.

All other opcodes pass through this component without any effect.

Properties

None.

Implementations

golay_encoder_us_ul (HDL)

Implementation of a [24,12,8] Golay encoder.

Example Application

<?xml version="1.0"?>
<!-- This file is protected by Copyright. Please refer to the COPYRIGHT file
     distributed with this source distribution.

     This file is part of OpenCPI <http://www.opencpi.org>

     OpenCPI is free software: you can redistribute it and/or modify it under
     the terms of the GNU Lesser General Public License as published by the Free
     Software Foundation, either version 3 of the License, or (at your option)
     any later version.

     OpenCPI is distributed in the hope that it will be useful, but WITHOUT ANY
     WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
     FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
     more details.

     You should have received a copy of the GNU Lesser General Public License
     along with this program. If not, see <http://www.gnu.org/licenses/>. -->
<application done="file_write">
  <instance component="ocpi.core.file_read" connect="golay_encoder_us_ul">
    <property name="filename" value="input.bin"/>
    <property name="messagesize" value="16384"/>
    <property name="messagesinfile" value="true"/>
  </instance>
  <instance component="ocpi.comp.sdr.coding.golay_encoder_us_ul" connect="file_write">
    <property name="checkbits_mask" value="15"/>
  </instance>
  <instance component="ocpi.core.file_write">
    <property name="filename" value="output.bin"/>
  </instance>
</application>

Dependencies

The dependency (generated via gen_golay_codewords_rom.py) for this worker is:

golay_codewords_rom.vhd

There is also a dependency on:

ieee.std_logic_1164

ieee.numeric_std

ocpi.types.all

Limitations

Limitations of golay_encoder_us_ul are: