News items for tag electronics - Koos van den Hout

2020-12-23 A bluetooth speaker that is also a serial port
I acquired a Blaupunkt BLP6100 Bluetooth speaker. Which turns out to support the following services via bluetooth:
  • Headset (audio for phone calls)
  • Handsfree operation (use buttons to accept, hangup or reject calls)
  • Audio sink (the main function of a bluetooth speaker)
  • Serial port
That last one I did not expect. I have tried opening the port with minicom and it will say carrier detect but sofar trying to wake it at 115200 or 9600 hasn't resulted in anything.

As a linux audio device it works fine. Or as a bluetooth speaker for my phone so I can listen to podcasts while walking around at home.

But the serial port makes me wonder!

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2020-12-05 Playing with a fully programmable LED strip
At work there is a sort-of competition for the best christmas decorations in the office. At the end of last year I considered doing something with programmable LEDs to 'participate' in this competition in 2020.

This year turned out somewhat different, but slowly my son is also somewhat interested in electronics, soldering and making the computer do something.

So I set out to find fully programmable LED strips. I found a good comparison of LED strips in a Youtube video: LED Strips, what's the difference? WS2811, WS2812B, 2812Eco, WS2813, WS2815, SK6812, SK9822. which compares the several available types and their pros and cons. After viewing this video and for my limited experiment I thought the WS2812B based LED strip would be the best choice. The next hurdle was controlling it and I found Connect and Control WS2812 RGB LED Strips via Raspberry Pi which has pointers to the right code.

I am not following the advice on that page about working with mains power cables. That looks dangerous.

I ordered a WS2812B based LED strip and a matching power supply for 5V 40Watt from a Dutch webshop and got it in a few days later. I was amused by the warning the webshop gave that a LED strip like this is for advanced users only because you have to add a controlling device and do all the programming. That is exactly what I intended to do!

Programming is in Python3, and I haven't written any Python code before. But with a lot of google searches and looking at samples I got the idea right.

I now have the LED strip blinking in exactly the patterns I want, including a nice pattern for a christmas tree. And it blinks 'MERRY CHRISTMAS' in morse code, because why not!

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2020-11-08 RF knowledge helps fix completely different problems
For work I currently spent quite a bit of time in video conferences. I have an external webcam from work which gives a better image than the built-in webcam, but it regularly started giving problems in the image. Hickups or blinking images, suggesting some communications problem between the webcam and the computer.

Since the webcam, a Microsoft lifecam studio, is still being sold and advertised as works good with Windows 10 I thought it wasn't the age of the webcam or a problem with the drivers.

So I tried a different solution which is almost the standard solution of a radio amateur for interference problem: add more ferrite to the cables. The USB cable is thin which suggests to me there is not a lot of room for good shielding. Pulling the USB cable through a ferrite core twice right after the USB plug made the problems go away.

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2020-10-10 The igate is igating
pi4raz igate running showing packet
pi4raz igate running showing packet
I dug into 'how to build code for the ESP32' and found Installing ESP32 Add-on in Arduino IDE (Windows, MacOS X, Linux) and since I have the Arduino IDE working enough for the previous project with a programmable microcontroller: the nanoKeyer morse keyer I did the steps to add ESP32 support.

I had to find the right settings for the specific ESP32 chip and since it is labeled "ESP-WROOM-32" I ended up at ESP-WROOM-32: Uploading a program with Arduino IDE and used the settings 'Board: FireBeetle-ESP32', 'Flash Frequency: 80 MHz', 'Upload Speed: 921600'.

The sourcefile to compile and upload to the ESP32 in the pi4raz igate is pa2rdk/APRS_IGate/APRS_IGate.ino.

I changed the definition of struct StoreStruct for a bigger wifi password (64 chars) and noticed that after uploading the updated code the last parts of the StoreStruct got mangled. I changed to #define EEPROM_SIZE 174 which seems to fix this.

I will admit to doing a bit of cargo-culting here: just following some google results and fiddling a bit until it works, with limited idea what I'm actually doing and what the effect of my changes is. The kind of weird results I got after growing the wifi password buffer suggested clearly to me that I was looking at some sort of buffer overflow, so I started looking for buffer sizes.

But the igate is now talking to the APRS network. First results visible at PE4KH-10 tracked on aprs.fi.

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2020-10-06 Finished and tested the electronics of another project: the igate
After finishing the Raspberry Pi ntp server in the weekend I continued on a long-running project: the PI4RAZ igate I started working on in June (and ordered in September 2019). I dragged the soldering iron, the soldering mat and lots of parts downstairs to work on it on Sunday evening. Soldering lots of pins to an Arduino nano is hard work.

I finished the last soldering on Monday evening and had a long and hard look at all the connections and redid a few. I used a multimeter to make sure three really close soldering islands weren't connected, found two with 0 ohms between them in both polarities so I fixed that issue.

After that I took the plunge of actually powering up the print and it looks good. The display shows output and I can walk through the setup when I connect a usb cable to the ESP32 module.

I can't make it run yet: the space for the wifi password in the ESP32 module is only 25 characters which is not enough for our home network. So I will have to look into changing the code (it has an update anyway: Software update iGate - PI4RAZ) and find a working way to program an ESP32 from linux.

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2020-09-02 An update to the home 1-wire network
For more than 12 years now(!) the house has temperature sensors using the 1-wire protocol. I recently redid some of the wiring between floors and I finally got around to rerouting the 1-wire network via this new route.

I also added a temperature sensor in the big room in the attic, we are thinking of using that room more often. To get an idea of how good that idea is we wanted to get an idea of the temperatures up there and that's what I have 1-wire sensors for! I soldered an 18b20 sensor to the end of a 4-wire flat phone cable, added it to the network and it's measuring.

So now 12 environmental temperatures are measured every 5 minutes: 9 in the house, one in the weather hut, one in the shed and one on the roof of the shed.

I also updated the 1-wire projects overview with how I use 4-wire flat phone cable in RJ45 connectors for 1-wire network. I had to look up how I did that previously before I could start adding new cables!

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2020-07-03 The GPS ticks!
I remembered the junkbox contains an active GPS antenna which I bought together with the gpskit gps unit in 2003(!). And some other bits and pieces included a SMA to BNC adapter so I put the little GPS antenna outside and connected it to the GPS/RTC Hat.

Before I was back behind a computer it was showing a location and within a few minutes it had a PPS pulse. I was used to cold start taking at least 15 minutes with the gpskit!

So I tested with ntpd talking to gpsd via shared memory. This gave an interesting offset between local gps time and a nearby ntp server.
$ ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*SHM(2)          .PPS.            0 l    6   64  377    0.000   -0.149   1.672
xSHM(0)          .GPS.            0 l    5   64  377    0.000  -104.51   1.943
+ntpritchie.idef 131.211.8.244    3 u  101   64  376    2.774    0.950  13.948
+metronoom.dmz.c 131.211.8.252    2 u   99   64  376   10.482   -0.844  10.638
$ ntpdc -c kern
pll offset:           -0.000136461 s
pll frequency:        -11.054 ppm
maximum error:        1.3748e-05 s
estimated error:      1.7071e-05 s
status:               2001  pll nano
pll time constant:    6
precision:            1e-09 s
frequency tolerance:  500 ppm
I'm not too happy about the fact that the GPS NMEA messages are seen as wrong, so I'm going to stop using gpsd and go for a setup optimized for timing.

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2020-07-01 A new home timeserver: GPS/RTC board
The Raspberry Pi GPS/RTC Expansion Board from uputronics came in today (thanks mailman!).

Next part needed: a gps antenna. But that's on backorder with another supplier.

Also needed: time to install raspbian on the Pi and start testing.

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2020-06-29 Newish electronics project: an igate
Some time ago I saw announcements of an igate build project from PI4RAZ, the amateur radio club in Zoetermeer. An igate is a system that receives APRS messages and forwards them to the Internet aprs servers.

There is a distinct lack of APRS coverage here in Utrecht, so more places that receive those messages and pass them to the Internet are a good idea. A specialized repeater to repeat them on the air would be even better, but that needs a special radio license which is one step too far and expensive at the moment for me.

The electronics came in months ago, but time to pick up the soldering iron and start with the hard part wasn't available. I started this monday with that hard part: soldering a VHF module on top using something close to surface mounting. Just with a lot more space between the soldering islands than real surface mount. Still needed good light and a magnifying glass to check my work constantly. I only had to desolder one small blob of solder which went in the wrong direction.

After that I soldered the resistors. That went fine. After that my eyes were too tired, but the first step has been made.

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2020-06-15 A new home timeserver on order
After earlier tries to have a nice GPS-based timeserver for my home network I noticed a simple but very effective GPS 'hat' for the Raspberry Pi, the Raspberry Pi GPS Hat from Uputronix. While the Pi's are already taking over the home network just one more could be a nice addition. In the longer run this will probably replace the shed computer.

So I ordered a Pi with an added dual-band WiFi adapter, a case, the GPS hat and a GPS antenna. The GPS hat has PPS support so I will get the time correct. With the instructions from 5 minute guide to making a GPS Locked Stratum 1 NTP Server with a Raspberry Pi it should be easy. If this all works I may even add the resulting Pi to the IPv6 NTP Pool.

Update 2020-06-16: SOS Solutions came back with some bad news: the uputronix Pi GPS Hat isn't available anymore. I'm now looking at the comparable adafruit hardware which is somewhat more expensive, but offers the same options.

Update 2020-06-18: And the adafruit hardware is also not available soon. I cancelled the GPS unit part of the order and I'm looking at sourcing a GPS module for the Pi from another source. The GPS hat which sossolutions no longer sells is originally from uputronics where a newer version of the Raspberry Pi GPS/RTC Expansion Board is listed as available on the site. Based on a ublox chipset which allows me access to a lot of the GPS data.

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