USB connected digital multimeter and graph plotting (UNI-T UT61E and sigrok)

Ever wanted to have nice plot (U/I curve, whatever) simply plotted?

I got 2 UNI-T UT61E with USB cable (50€ each)

With sigrok you can easily get data from many device with a single command:

sigrok-cli –driver=uni-t-ut61e:conn=BUS.DEVICE -O analog  –continuous

Where BUS and DEVICE is replaced with the output of lsusb

lsusb
Bus 002 Device 002: ID 8087:8001 Intel Corp.
Bus 003 Device 086: ID 1a86:e008 QinHeng Electronics HID-based serial adapater
Bus 003 Device 087: ID 1a86:e008 QinHeng Electronics HID-based serial adapater

In my case, as I’ve 2 devices, so 2 different commands are used:

sigrok-cli –driver=uni-t-ut61e:conn=3.86 -O analog  –continuous

sigrok-cli –driver=uni-t-ut61e:conn=3.87 -O analog  –continuous

 

But what about logging in the same file the two ouputs simultaneously?

Here comes the magical function: paste and joined pipe:

paste <(sigrok-cli –driver=uni-t-ut61e:conn=3.86 -O analog  –continuous) <(sigrok-cli –driver=uni-t-ut61e:conn=3.87 -O analog  –continuous) > measure.csv

 

I’ll let you deal with the uber simple csv processing with octave or libreoffice calc (mV, mA range condition, etc…), as this blog entry is mainly used as a personal notepad.

 

Note: if you have trouble connected with sigrok, with an error. You may need to disable the power feature, with the script pointed by blog.philippklaus.de

#!/bin/bash
# see http://www.erste.de/UT61/index.html
for dat in /sys/bus/usb/devices/*; do 
  if test -e $dat/manufacturer && grep -q "WCH.CN" $dat/manufacturer; then
    echo "Suspending ${dat}."
    echo auto > ${dat}/power/control
    echo 0 > ${dat}/power/autosuspend 
  fi      
done

Process audio file with Sox using Room EQ Wizard filter file

Rationale: compensate a speaker response curve (gain and phase) on a audio file.

Just came accross REW (Room EQ Wizard) (Linux, Windows, Mac), it let you plot the output of your speakers, then create a filter to compensate the flaws.

Once you created your finely tuned speakers, Export-> Filter as text file.

Then, it’s time to process the audio file with this filter, using the amazing Sox:

sox -q input_file.wav output_file.wav `awk ‘$4==”PK” { gsub(/,/,””,$6 );val=$6;printf ” equalizer “val” “$12″q “$9}’ val=”%’6.3f” REW_filter.txt`

That’s it: you have a outputfile with the correct compensation for your just analysed speaker.

Of course this method is for non-real time need.

microSD card reflow: quick and dirty PCB with Kicad

Ever wanted to add a lot a flash memory to a small microcontroller? NOR flash or EEPROM are ok, but only for small size. For Gbit range, you need NAND, and with NAND comes CCR, LUT, wearleveling, etc… Furthermore, they are darn expensive in small volume.

SD and microSD card are very interesting: they cost nothing, and you just need a SPI interface as the controller is included.

Last night, I thought: “why not reflow a complete microSD card”, and save the cost of the socket, and PCB footprint size. As the card is composed of the same resin as chip casing and pins are flat bellow the microSD card and even gold plated, fore sure it should not be a problem to bring this to 270°C for 2-3 min….

Let’s try!

Here is the pinout

Then let’s create a small board, to try the reflow of a micro SD card and give access with some 2.54mm header.

Lets open Kicad and start with the schematic with Eeschema:

Then PCB new for the board layout:

Let’s submit the gerber files to OSH Park

Total including USPS post mail: 4.10€

That was my fastest board made ever, 1h30 from searching the pinout to the confirmation email!

See you back in few week for the oven reflow test!

Update: the board and the reflow!

First, let’s clean it and apply some flux:

Then some solder on the pads, and flux again:

Time to turn the heating plate and IR reflow on:

Just stir it a bit while it’s hot:

Houston, we have a reflow!

Then time to test: lets scavenge a super cheap reader microSD card reader:

And plug it: IT WORKS! After 3 min under the IR station, it does work.

I think I’ve to increase the pad size, in order to maximize the solder paste.

Now I’m confident sending to production, as I’ve quite a lot of theses cards in trays, ready for pick and place:

 

Simple CNC desktop router workflow and example

If you have access to a simple desktop mill/router, and you are not into mechanical part design, here is a very simple workflow:

Workflow

Sofware

You will only need free/open source program:

Example

In order to illustrate this example, we are going to make a case for a nice Nixie Clock from PV Electronics

A simple Ikea-hack will do for the wooden box: DRAGAN 2-piece bathroom dish set, bamboo

The front panel is milled

And fitted in place

The 2 stainless steel feet are from Ikea again

Thanks Dan Heeks for the very good software.

Happy milling!

Files are available here.

Dirt cheap DIY Smartphone Bike Mount

I use my bike quite a lot to commute in the city.

And, sometimes, to find the good street (believe me, in France, it’s not that easy) with the GPS while riding is tricky.

So I’ve been looking on the Internet to find THE good smartphone holder: unfortunately they are either bulky or expensive (and most of the time both)

Except this one: the Finn, a $9.95 silicone mount:

But buying things is not the hacker’s way.

So let’s take the design on Inkscape:

Download the pdf file here and print it on a A4 paper sheet without scaling.

Tape it with carpet double side tape on an old bike tube.

Cut the tube by cutting the paper pattern at the same time and remove the paper and tape.

Rub’it on your bike and let’s ride!

Important: the mount has to go on the back of the handle bar, as shown on the step 3.

 

 

XCSoar: generate custom maps

Introduction

XCSoar is an Open Source software for tactical glide computer: run it on any PDA/Smartphone/eBook and you have a powerfull computer for sailplane, paradlider and hang glider. (see previous post about adding a GPS to an eReader)

Generated map can be downloaded here

The geo file format used by XCSoar are:

  • elevation geotiff raster with altitude encoded (custom format)
  • waypoints
  • airspace
  • any shapefile

We will use the latest to add custom geo referenced information on XCSoar (in this case, paragliding skyways from thermal.kk7)

Software requirement

 Processing files

#remove and create temp folder for file processing
rm -rf tmp/; mkdir tmp/
#convert PNG+PGW to GeoTiff and resize for faster processing (resize to any % or none)
gdal_translate ./skyways_all.png tmp/skyways_all.tif -outsize 50% 50%
#vectorize contour to shapefile red layer
gdal_contour tmp/skyways_all.tif tmp/skyways_all_r.shp -i 50 -b 1
#vectorize contour to shapefile green layer
gdal_contour tmp/skyways_all.tif tmp/skyways_all_g.shp -i 80 -b 2
#vectorize contour to shapefile blue layer
gdal_contour tmp/skyways_all.tif tmp/skyways_all_b.shp -i 200 -b 3

 

Visualisation with QGIS

Import from Layer->Add Vector Layer and select your 3 files

Then if everything is fine, save the 3 as Shapefiles:

Place the generated file into the XCM (XCSoar compressed archive map)

Dont forget to edit the topology.tpl to add the names of the new files:

You can edit color (RGB, 0-255)  and transparency (0-255)

The order is important: element are displayed from top to bottom (first to last)

Result

Original raster file, PNG + PGW format.

Generated shapefile maps in XCSoar (desktop version)

Same in XCSoar but eReader version optimised for black and white gray levels.

Generated map can be downloaded here

USB motion sensor (PIR) to activate monitor

I have an always on net-book for weather forecast (yeah, when paragliding, you need the most up to date forecast)
It basically displays a full screen custom web-page with time and date and weather.

Its always on, not really good for the back-light and energy consumption.

So I got the idea of plugging a PIR sensor to wake up the screen when someone approach it.

Take an Arduino Micro Pro (4€ for the Chinese version), a PIR sensor (2€), a Hammond case (1€) and an USB A male from scrap (0€).

Let’s give a try, with a basic wiring, and this sketch to emulate keyboard thanks to it’s USB HID, the Arduino Micro Pro is a must.

Updated 05-01-2017:

  • code with USB wakeuphost and capslock instead of ctrl
  • green TX led always on
  • orange RX led only on motion
#include <Keyboard.h>

#define SENSOR_PIN 10   // Senor state input pin
#define RX_LED_PIN  17  // The RX LED has a defined Arduino pin
static bool sensor_previous_state = false;

void setup()
{
  pinMode(SENSOR_PIN, INPUT);  // PIR sensor pin as input
  pinMode(RX_LED_PIN, OUTPUT);     //  RX LED as an output
  digitalWrite(RX_LED_PIN, HIGH);  //  RX LED off
  TXLED0;                     // switch on TX green to show init/powered up (only available by macro)
  sensor_previous_state = digitalRead(SENSOR_PIN); // get sensor initial state (can be already true)
}

void loop()
{
  bool sensor_current_state = digitalRead(SENSOR_PIN);
  if ( sensor_previous_state == false   // looping until we detect a rising edge
       && sensor_current_state == true) {// when sensor state is trigged, it takes about 20 sec to recover
    digitalWrite(RX_LED_PIN, LOW);   // set the LED on
    USBDevice.wakeupHost();
    Keyboard.press( KEY_CAPS_LOCK );
    Keyboard.release( KEY_CAPS_LOCK );
    TXLED0;                     // great hackery in this: we have to force down the TXLED
    delay(1000);                  // wait a bit for the led
  } else {
    digitalWrite(RX_LED_PIN, HIGH);    // set the LED off
    TXLED0;
  }
  sensor_previous_state = sensor_current_state;
}
2017 update: lightguide for green and orange LEDs:
p70105-114417
Update: LED lightguides from the scrap box
And voila!
Quite nice, discrete and works very well, for about 10€/$.

Kobo mini GPS mod with 3D printed case

Introduction

XCSoar is an amazing software for sailplane, hang-glider and paraglider. But lack the proper hardware with the following features:

  • sun readable ( eink)
  • usable with gloves (anything but capacitive)
  • long battery life
  • running android/linux
  • GPS and/or bluetooth
  • dirt cheap (yes 50€/£/$ for this hardware is dirt cheap)

The Kobo Mini is a very good eReader (unfortunately no more retailed) appears to be meeting all theses requirements except the GPS.

Hardware

Component list

You will need for this mod:

  • Kobo Mini reader
  • GPS module with serial output or a BlueFlyVarioTTL
  • 3D printed spacer
  • extra battery
  • iron solder (a good one, I use this)
  • solder wire and a piece of flat ribbon cable

( By the way, the way Kobo handles the first boot is just crap: no I don’t want to register my device online or anything, just to drag and drop my own ePub books, thanks! )

GPS module instructions

Solder the MTK3339 GPS breadboard (with a piece of flat ribbon cable such as IDE, Floppy, whatever..)

KOBO to GPS MTK3339 wiring

KOBO - MTK3339
KVCC <-> VCC
TP2 <-> BACKUP (TP2 is just below the battery connector)
RX  <-> TX
TX  <-> RX
GND <-> GND

Don’t forget to cross RX<->TX and TX<->RX (the eternal embedded engineer question, RX TX….)

Just in case you wondered, yes the BACKUP does accept 4.2V (TP2 is battery test point, so not regulated), and not just 3.3V (have a look on the MTK3339 datasheet)

 

You can download the STL of the “Kobo mini Case Spacer II” on Thingiverse

And download the gps cover

The STL (in mm) file is then printed by Shapeways for just 22€ incl P&P, delivered in about a week: very cool!

 

You will need 5screws, size M1.6 and 8mm (my 10mm were too long, I had to cut them with a pair of pliers)

All fit snugly, even the original back cover.

Add ON/OFF button to switch the GPS power (a simple SMD switch to the GPS’s VCC)

So I can still use it as a regular eBook without draining the battery and without the blue led blinking in the dark.

The switch is accessible by nails as it’s quite recessed.

Add a label for even more clarity.

BlueFlyVarioTTL instructions

Or this set for the BlueFlyVarioTTL, download the cover: And download the spacer for the battery:

The file STL (in mm) is then printed by Shapeways for just 19€.

You will need 5screws, size M1.6 and 8mm (my 10mm were too long, I had to cut them with a pair of pliers)

Solder 0.1″ header

And remove the black plastic from the header

Drill 5 holes with a 1mm bit, using the module as guide

Insert it

Then solder the 5 wires

Use 2 parker 3mm screws

That’s it

Battery for GPS module or BlueFlyVarioTTL

The original battery of 1000mAh gives from 4 to 6h, which can be quite a limitation.

The original 1000mAh beside the new 3800mAh battery

The new battery li-ion from AliExpress measure 4x75x86mm, with 3.7V and 3800mAh. Warning, you need the 3D printed spacer to use this battery.

I removed the original one and harvested it’s connector for the new one.

To remove the original double side taped battery, use an air dryer or so (warning not a hot air gun, it would be too hot)

The new battery is held firmly with double sided tape and now it last about 20hours of flight: perfect. (but the drawback: it is quite heavy to read in the bed now….)

Software

They are tons of tutorials on the web, I wont describe it any further, but simply put, it works this way:

Download XCSoar KoboRoot.tgz: http://www.xcsoar.org/download/data.html

And place it on the kobo root file system using any file browser, restart and you are done.

GPS configuration

GPS module

For the GPS module, set the device to /dev/ttymxc0 at 9600bauds, generic drivers.

BlueFlyVarioTTL

For the the BlueFlyVarioTTL, set the device to /dev/ttymxc0 at 57900bauds, blueflyvario drivers.

“GPS waiting for fix” should appear, note that the first fix can take up to 15min (30s later on, thanks to BACKUP power supply to keep the RTC and ephemeris)

You can change the sink alarm and volume:

  • Enable Wifi, and Telnet,
  • Connect to with telnet to the Kobo,
  • send the following commands:

stty ospeed 57600 ispeed 57600 -F /dev/ttymxc0 #configure baudrate

stty -F /dev/ttymxc0 raw #set device as raw

echo ‘$BFS 2500*’>/dev/ttymxc0 # sink alarm to -2500cm/s

echo ‘$BVL 70*’>/dev/ttymxc0 # volume to 70%

 

Maps

Then download the map: http://www.xcsoar.org/download/data.html

Download hotspot (probable thermal) as way-points (wpt format), and set the file in way-points configuration): http://thermal.kk7.ch/, save all this map file to the correct XCSoar folder.

I created custom map content to have paragliding skyways displayed on XCS:

More detail here: http://www.dotmana.com/weblog/2014/07/xcsoar-generate-custom-maps/

And here you are, you have a comp GPS for less than 100€/$/£ for paragliding/sailplane, in about an hour of work.

Result with GPS module

Result with BlueFlyVarioTTL

(note the green led flashing when lifting)

leGPSBip: solar vocal GPS alti vario

This device is ready to use with the Kobo or any smartphone, simply connect it and voila! You have a fully GPS/altimeter enabled smartphone.

It also act as a standalone vocal GPS variometer when not connected, pretty convenient:

More info here: http://www.lebipbip.com/legpsbip-solar-vocal-gps-alti-vario/

Links and references

XCSoar forum: http://forum.xcsoar.org/viewtopic.php?f=3&t=1242

Kobo GPS mod on another blog: http://www.extreme-nature.de/?p=9114

M1.6×8 screws: http://www.ebay.co.uk/

Commercial Kobo mod: http://www.goflyinstruments.com/gofly-project-v4/

XCSoar forum about this mod: http://forum.xcsoar.org/viewtopic.php?f=3&t=1404&start=10

Li-ion battery on AliExpress: http://www.aliexpress.com/item/L002-3-7V-3800mAH-457992-PLIB-polymer-lithium-ion-battery-Li-ion-battery-for-tablet/1477811584.html

BlueFlyVarioTTL http://blueflyvario.blogspot.com.au/2014/11/blueflyvariottlgpsv10-released.html

BlueFlyVarioTTL case: http://blueflyvario.blogspot.com.au/2014/07/blueflyvariottlgps-simple-case.html

Mini Solar vario: http://www.lebipbip.com/

STL archive: Kobo_Mini_case