Contact: info@pavlin.si
I have some I2C sensors which are capable of running from low supply voltages. Host microcontroller has 3,3 or 5V supply, which is usually out of absolute maximum range, when I2C device is supplied with e.g. 1,8V. The sensor is usually very low power, which means simple emitter follower could do the low voltage supply.
The circuit schematic is shown in following drawing (click to enlarge):
Full bunch of wires is hanging from each HAM station and PC connected to the station: CAT, audio, each via dedicated interface for isolation or level shifting. Additional mess is with parrots or digital interfaces for digital mode. I wanted simple solution, which can be conected to PC via single USB cable.
I was looking for simple audio CODEC and found WM8731. To have enough processing power for some simple DSP audio I chose cortex M4F microcontroller. There is also micro-SD on the board for audio recording and playback, two mini-DIN connectors with YAESU pinout and galvanic isolation for USB. I stareted this project few months ago. I will add posts when I will make progress with module programming.
The PCB is 80x45mm.
Here is schematic: modem
And PCB layout: lingva
Stay tuned for further progress reports.
The software will be published on git.
I recently set up a APRS gateway. Check instructions in older posts. In the script pymultimonaprs you can set weather when set in a json-file. eg: “weather”: “/path/to/weather.json”. I live next to the automated weather station for our city. Instead of building own WX I decided to use the data from this nearby station. The data is provided in XML from our national agency ARSO. The data is available for some major cities in Europe, too.
Main idea was to prepare PHP script to parse the XML data and prepare text file, which is acceptable for pymultimonaprs. Next step is to wget this text from some server and copy it to the raspberry pi with cron job.
This page will give you an example how to:
Continue reading ‘Add weather report from local weather station to APRS node’ »
This is part two (here is part one) of the tutorial how to use Raspberry-Pi in APRS gateway.
In part one I explain how to install OS for Raspberry Pi and get RTL dongle up and running, which enables radio reception and listening received signal with FM demodulator on audio jack (simple FM receiver). For next steps you will need HAM licence with own call sign. Mine is S54MTB.
Continue reading ‘Raspberry Pi + RTL SDR dongle = APRS Rx only gate (Part Two – Decoder)’ »
I have couple of raspberry pi’s laying around doing nothing useful. I decided it’s time to use it better than dust collectors. This tutorial is placed here for reference for any OM who would like to setup APRS Rx only node based on R.pi. Here’s what you’ll need (hardware):
… and software:
Continue reading ‘Raspberry Pi + RTL SDR dongle = APRS Rx only gate (Part one – FM Radio)’ »
I was looking for dummy load on ebay for HF testing. All dummy loads were too expensive. Then I found bag of thick film resistors. Unfortunately they were 820 ohm, which is not optimal for 50 ohm load, but close enough. Then I constructed two PCBs.
The construction is simple…
At the end I would like to put everything into oil bath to make it more suitable for high power testing.
The small SMA connectior is for measuring via the 1:10 voltage divider.
Here’s altium PCB for the two boards: dummyload (31.10.2014 21-23-06)
During summer vacation in 2014 we had new piece of equipment for portable work. The QRP rig FT817ND is excellent for quick setup and has low power consumption to operate from battery for many hours.
Our Balkan tour started in Korčula island, where Gal S57GP and myself S54MTB operated from 27.08.2014 to 02.08.2014 with 9A/ prefix.
I bought 6 alluminium tubes, 2m long, diameter from 45 down to 20mm for 40m quarter wave vertical antenna. This 10m simple construction collapses to 2m pack with nly 45mm diameter. The base is made from PVC plastic isolator, which is fixed to alluminium plate with 4 M6 screws and additional nut, placed inside the plastic hole, which is normally used to fix the steerer tube on the bicycle.
Photos are worth more than 1000 words…
This is next step in developing virtual COM port application. There arre two other parts required:
STM32F4 discovery – Keil example step-by-step
and first part of virtual com port tutorial:
STM32F4 discovery – Virtual COM port, step-by-step
In this example we will add DTR and RTS signals to two GPIO pins. Next, we will add simple command line interpreter for simple communication with the micorcontroller.
Continue reading ‘STM32F4 Discovery virtual com port – part II’ »
This is next step in developing applications with STM32F4 Discovery board and Keil tools. This step-by-step tutorial describes how to prepare the simple application which communicates with PC using virtual COM port. This application is based on LED blinky desribed in first tutorial. We will continue with same project. You can copy/paste the entire folder to new one or continue inside the existing “blinky”.
Continue reading ‘STM32F4 discovery – Virtual COM port, step-by-step’ »