Hardware tips

Quadrature counter

• https://www.allaboutcircuits.com/industry-articles/designing-quadrature-encoder-counter-with-spi-bus/

Frequency counting

• RF https://github.com/swharden/RasPi-Frequency-Counter
• https://blog.adafruit.com/2021/04/28/a-low-cost-100mhz-frequency-meter-technoblogy-microchipmakes/
• pyhon https://atman-iot.com/blog/raspberry-pi-benchmark/
• IC https://www.ti.com/lit/ds/symlink/sn74lv8154.pdf

ATTiny frequency counter

• http://www.technoblogy.com/show?20B4

pico frequency counting

• https://github.com/phoreglad/pico-MP-modules/tree/main/PWMCounter
• https://github.com/dpwe/FreqCountRP2

pi frequency counting

• http://abyz.me.uk/rpi/pigpio/index.html

Clock Calendar

• https://www.mouser.com/datasheet/2/302/PCF8593-1127704.pdf

pi GPIO Performance

• https://codeandlife.com/2012/07/03/benchmarking-raspberry-pi-gpio-speed/

clock generator

• https://www.adafruit.com/product/2045
  • https://github.com/etherkit/Si5351Arduino

VFO

• https://projecthub.arduino.cc/CesarSound/3bd1c1cc-1971-41e9-890e-0451c35720e0
• https://gist.github.com/NT7S/24206e12342e4631e2a7
• https://qrp-labs.com/vfo.html
• https://www.qsl.net/pa2ohh/20vfobfo.htm