Posts

Crude low frequency counters with Raspberry Pi Pico

Image
Crude low frequency counter Used two state machines to generate two square waves as signal sources. Frequency counter measured these two frequencies. Frequency counter input       Pico pin 20 (GPIO-15) 40 Hz sq.wave signal source on      Pico pin 21 (GPIO-16) 25 kHz sq.wave signal source on    Pico pin 22 (GPIO-17) 25 kHz was maximum frequency that could be measured. With 25 kHz input, reading varied from 25000 Hz to 25004 Hz Number of interrupts   in one second  were counted to get frequency. MicroPython code: ##################### # Filename CrudeFc1.py import time from machine import Pin import  rp2 # global variable H2L = 0 # Interrupt handler (ISR) def h2l( void ):     global H2L     H2L = H2L + 1           def frequency():     global H2L     fin.irq ( handler = None ) # Int. disabled     H2L = 0     fin.irq ( handler = h2l, trigger=Pin.I...
Post a Comment
Read more

Raspberry Pi Pico basic health check

Image
Health check of newly arrived Raspberry Pi Pico  Pico micro-controller board arrived a few days ago. Cost at doorstep was Rs.449/- ( May 2022). It came with soldered header pins and USB cable. A few codes were tried on it as basic health check of the newly arrived board.  Checking was carried out on a Raspberry Pi 4 B ( 8 GB RAM ) PC. Codes used in testing were taken from examples of different sites and discussion groups. I am new to Python! File rp2-pico-latest.uf2 was downloaded on Desktop. $ cd Desktop  ~/Desktop $ wget -c https://micropython.org/download/rp2-pico/rp2-pico-latest.uf2                Pico was wired up on a small breadboard and was connected with Raspberry Pi PC with USB cable.  A push to make switch was added between RUN and GND . Thonny Python IDE was started on Raspberry PI. Thonny was switched to regular mode (top right corner). Thonny version number (right bottom corner, Python 3.9.2 in my PC) was clicked to select interp...
Post a Comment
Location: 874V+CXW, Hijli Co-Operative Society, Kharagpur, West Bengal 721306, India
Read more
Image
  Booting multiple ISO images from USB pendrive using Ventoy Came across Andy's ( KB1OIQ ) HAM Linux live image  and wanted to check it out. Raspberry Pi 4 B is my main shack PC. Andy's HAM Linux is not designed to run on Raspberry Pi.  Have one old PC powered by AMD chip. This is one of the lines KNOPPIX live CD spewed out while booting. knoppix@Microknoppix:~$ dmesg | grep AMD [    9.579506] powernow-k8: Found 1 AMD Sempron(tm) 145 Processor (1 cpu cores) (version 2.20.00) The AMD PC is multi-boot and runs Linux Mint 18.2, Puppy Slacko 6.3.2 frugal installation and Debian Linux Buster. Hard disk has some unused partitions. Different kinds of Linux are installed on these to find out how they run on old hardware.  CD and DVD drives on this old PC are no longer working reliably.   Booting from USB drive (pendrive) is a better option now. Googled and found  Ventoy that can boot more than one ISO image from USB pendrive   Booted AMD P...
Post a Comment
Read more

Direct Conversion Receiver using sub-harmonic mixer

Image
Used this sub-harmonic mixer, popularised by Vladimir Polyakov (RA3AAE), to make a 40M direct conversion receiver.  Sub-harmonic mixer Example:    Local oscillator is set to 3572.5 kHz to receive 7145 kHz in this sub-harmonic mixer. LO leakage to antenna causes most problems in direct conversion receivers. Anticipated little  problem because LO and Rx frequencies are different in a sub-harmonic mixer. Tried a single tuned front end without RF amplifier, DDS VFO as LO, a simple 12 Volt power  supply and audio amplifier. Audio amplifier was followed by a LM386 speaker amplifier.   Result was an unusable radio with strong  hum. 2nd harmonic of LO was reaching the antenna or the power supply had ripple ?  Assumed both and applied Grandma-approved home remedies. RFC with ferrite core, bypassed with 100nF ceramic disc capacitor, in every conceivable point 10000uF capacitor after rectifiers of power supply 18 Volt from first regulator, goes to radi...
1 comment
Location: Hijli Co-Operative Society Ghagra, Near Soap factory, Kharagpur, West Bengal 721306, India
Read more