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Gate Array Learn
apt install yosys fpga-icestorm nextpnr-ice40 verilator flashrom
make
doas make load
Raspberry Pi UART
Enable serial communication in raspi-config.
UART
stty -F /dev/ttyUSB1 3000000 raw cs8
hexdump -ve '1/1 "%u\n"' /dev/ttyUSB1 | pv > pcm.txt
pv /dev/ttyUSB1 > pcm.raw
hexdump -ve '1/1 "%u\n"' pcm.raw > pcm.txt
play -r 48k -e unsigned-integer -b 8 -c 1 pcm.raw
References
Adafruit PDM Microphone Breakout
https://learn.adafruit.com/adafruit-pdm-microphone-breakout/
Cascaded Integrator-Comb (CIC) Filters
https://www.dsprelated.com/showarticle/1337.php
CIC filter in Verilog
https://github.com/ericgineer/CIC/blob/master/CIC.v
Pulse Density Modulation
https://curiouser.cheshireeng.com/2015/01/21/pdm-in-attiny85-source-code/
https://en.wikipedia.org/wiki/Pulse-code_modulation
https://tomverbeure.github.io/2020/10/04/PDM-Microphones-and-Sigma-Delta-Conversion.html
https://tomverbeure.github.io/2020/12/20/Design-of-a-Multi-Stage-PDM-to-PCM-Decimation-Pipeline.html
RMS in FPGA
https://www.controlpaths.com/2022/07/18/true-rms-compute-in-fpga/
Verilator
https://www.veripool.org/verilator/
https://verilator.org/guide/latest/
Verilog by Example (Blaine C. Raedler 2021)
http://readler.com/books2.html
TinyTapeout submission
There are Github Actions that build the design. GDS output most interesting
https://tinytapeout.com/guides/workshop/create-your-gds/
https://github.com/jonnor/ttysky25a-pdm-microphone
tt-sky25a shuttle repo
https://github.com/TinyTapeout/tinytapeout-sky-25a
This seems like the correct template for sky25a submissions
But CI builds failing as of June 20, 2025!
https://github.com/TinyTapeout/ttsky-verilog-template
Others have submitted using to sky25a using these older templates
https://github.com/TinyTapeout/tt09-verilog-template
https://github.com/TinyTapeout/tt10-verilog-template
Examples
https://github.com/urish/tt09-giant-ring-oscillator
https://github.com/RVCE-ECE-Shylashree/TT10_LogAFPM-16
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