I am currently coding an open-source multi-universe USB-DMX512-interface (https://github.com/OpenLightingProject/rp2040-dongle). DMX512 has the advantage that unused channels (and there are usually plenty of them just have the value of 0. That makes the amount of data shrink by a large amount if compressed.
Of course, the rp2040 is an "embedded" processor, so it's not the fastest thing to run code and memory is also pretty limited. So what to do if there are plenty compression algorithms out there to choose from? Benchmark them :)
Please be aware that my use case is pretty limited and constrained: I'm "only" compressing 512 byte each and I want to do so FAST (no longer than 2ms). Your use case and requirements might be hugely different.
Welcome to rp2040-compressiontest
pll_sys = 250001kHz (= ~250MHz)
Initializing test vectors ... 495µs
8 test vectors:
ALL_ZERO
ALL_ONE
SAWTOOTH_SMALL
SAWTOOTH_MEDIUM
SAWTOOTH_LARGE
ALL_RANDOM
ALTERNATING_RANDOM_ZERO
BLOCKS_8RANDOM_8ZERO
Initializing compression algorithms ... 95µs
5 compression algorithms:
HEATSHRINK
ZLIB
ZSTD
SNAPPY
BROTLI
BENCHMARK RUN START
HEATSHRINK:
ALL_ZERO: Runtime: 268µs; Insize: 512; Outsize: 16, Ratio: 3% Decompress time: 151µs Verification: PASSED
ALL_ONE: Runtime: 236µs; Insize: 512; Outsize: 18, Ratio: 3% Decompress time: 131µs Verification: PASSED
SAWTOOTH_SMALL: Runtime: 257µs; Insize: 512; Outsize: 19, Ratio: 3% Decompress time: 123µs Verification: PASSED
SAWTOOTH_MEDIUM: Runtime: 281µs; Insize: 512; Outsize: 34, Ratio: 6% Decompress time: 141µs Verification: PASSED
SAWTOOTH_LARGE: Runtime: 382µs; Insize: 512; Outsize: 86, Ratio: 16% Decompress time: 205µs Verification: PASSED
ALL_RANDOM: Runtime: 1193µs; Insize: 512; Outsize: 576, Ratio: 112% Decompress time: 824µs Verification: PASSED
ALTERNATING_RANDOM_ZERO: Runtime: 8384µs; Insize: 512; Outsize: 479, Ratio: 93% Decompress time: 747µs Verification: PASSED
BLOCKS_8RANDOM_8ZERO: Runtime: 2109µs; Insize: 512; Outsize: 348, Ratio: 67% Decompress time: 563µs Verification: PASSED
ZLIB:
ALL_ZERO: Runtime: 670µs; Insize: 512; Outsize: 14, Ratio: 2% Decompress time: 166µs Verification: PASSED
ALL_ONE: Runtime: 537µs; Insize: 512; Outsize: 14, Ratio: 2% Decompress time: 100µs Verification: PASSED
SAWTOOTH_SMALL: Runtime: 514µs; Insize: 512; Outsize: 15, Ratio: 2% Decompress time: 94µs Verification: PASSED
SAWTOOTH_MEDIUM: Runtime: 569µs; Insize: 512; Outsize: 30, Ratio: 5% Decompress time: 103µs Verification: PASSED
SAWTOOTH_LARGE: Runtime: 806µs; Insize: 512; Outsize: 81, Ratio: 15% Decompress time: 130µs Verification: PASSED
ALL_RANDOM: Runtime: 2042µs; Insize: 512; Outsize: 523, Ratio: 102% Decompress time: 86µs Verification: PASSED
ALTERNATING_RANDOM_ZERO: Runtime: 1994µs; Insize: 512; Outsize: 393, Ratio: 76% Decompress time: 501µs Verification: PASSED
BLOCKS_8RANDOM_8ZERO: Runtime: 1877µs; Insize: 512; Outsize: 331, Ratio: 64% Decompress time: 227µs Verification: PASSED
ZSTD:
ALL_ZERO: Runtime: 610µs; Insize: 512; Outsize: 19, Ratio: 3% Decompress time: 307µs Verification: PASSED
ALL_ONE: Runtime: 508µs; Insize: 512; Outsize: 19, Ratio: 3% Decompress time: 139µs Verification: PASSED
SAWTOOTH_SMALL: Runtime: 472µs; Insize: 512; Outsize: 19, Ratio: 3% Decompress time: 130µs Verification: PASSED
SAWTOOTH_MEDIUM: Runtime: 466µs; Insize: 512; Outsize: 33, Ratio: 6% Decompress time: 117µs Verification: PASSED
SAWTOOTH_LARGE: Runtime: 543µs; Insize: 512; Outsize: 83, Ratio: 16% Decompress time: 128µs Verification: PASSED
ALL_RANDOM: Runtime: 578µs; Insize: 512; Outsize: 522, Ratio: 101% Decompress time: 63µs Verification: PASSED
ALTERNATING_RANDOM_ZERO: Runtime: 1422µs; Insize: 512; Outsize: 379, Ratio: 74% Decompress time: 654µs Verification: PASSED
BLOCKS_8RANDOM_8ZERO: Runtime: 1822µs; Insize: 512; Outsize: 345, Ratio: 67% Decompress time: 235µs Verification: PASSED
SNAPPY:
ALL_ZERO: Runtime: 191µs; Insize: 512; Outsize: 28, Ratio: 5% Decompress time: 235µs Verification: PASSED
ALL_ONE: Runtime: 128µs; Insize: 512; Outsize: 28, Ratio: 5% Decompress time: 103µs Verification: PASSED
SAWTOOTH_SMALL: Runtime: 122µs; Insize: 512; Outsize: 29, Ratio: 5% Decompress time: 99µs Verification: PASSED
SAWTOOTH_MEDIUM: Runtime: 120µs; Insize: 512; Outsize: 43, Ratio: 8% Decompress time: 75µs Verification: PASSED
SAWTOOTH_LARGE: Runtime: 133µs; Insize: 512; Outsize: 90, Ratio: 17% Decompress time: 58µs Verification: PASSED
ALL_RANDOM: Runtime: 74µs; Insize: 512; Outsize: 517, Ratio: 100% Decompress time: 46µs Verification: PASSED
ALTERNATING_RANDOM_ZERO: Runtime: 76µs; Insize: 512; Outsize: 517, Ratio: 100% Decompress time: 34µs Verification: PASSED
BLOCKS_8RANDOM_8ZERO: Runtime: 249µs; Insize: 512; Outsize: 359, Ratio: 70% Decompress time: 243µs Verification: PASSED
BROTLI:
ALL_ZERO: Runtime: 733µs; Insize: 512; Outsize: 20, Ratio: 3% Decompress time: 568µs Verification: PASSED
ALL_ONE: Runtime: 594µs; Insize: 512; Outsize: 20, Ratio: 3% Decompress time: 536µs Verification: PASSED
SAWTOOTH_SMALL: Runtime: 679µs; Insize: 512; Outsize: 21, Ratio: 4% Decompress time: 408µs Verification: PASSED
SAWTOOTH_MEDIUM: Runtime: 841µs; Insize: 512; Outsize: 67, Ratio: 13% Decompress time: 438µs Verification: PASSED
SAWTOOTH_LARGE: Runtime: 1086µs; Insize: 512; Outsize: 162, Ratio: 31% Decompress time: 531µs Verification: PASSED
ALL_RANDOM: Runtime: 2412µs; Insize: 512; Outsize: 516, Ratio: 100% Decompress time: 134µs Verification: PASSED
ALTERNATING_RANDOM_ZERO: Runtime: 2168µs; Insize: 512; Outsize: 427, Ratio: 83% Decompress time: 827µs Verification: PASSED
BLOCKS_8RANDOM_8ZERO: Runtime: 2027µs; Insize: 512; Outsize: 410, Ratio: 80% Decompress time: 881µs Verification: PASSED
This project uses the usual toolchain for the RP2040-based projects. You will need a (cross-)compiler for the ARM Cortex M0 and the pico-sdk. For details how you can achieve this on your system, please refer to https://datasheets.raspberrypi.org/pico/getting-started-with-pico.pdf
Basically, once all requirements are met, run:
mkdir build
cd build
cmake ../src
make
This should result in a file called rp2040-compressiontest.uf2 that can be copied to the Pico when it's in bootloader-mode.
This source code, schematics and board layouts is licensed under the GPL.
Parts taken and modified from TinyUSB (tusb_config.h, usb_descriptors.c) is:
* The MIT License (MIT)
* Copyright (c) 2019 Ha Thach (tinyusb.org)