Something about the Software…

Now that the first 16 devices are shipped, it is also time to write something about the software:

Currently there is an integration for Android in the quite popular xDrip-plus, which is developed by outstanding people completely OpenSource.

The current releases of xDrip + are available here:

Once the app is installed, select the “LimiTTer” under “Settings” -> “Hardware Data Source”, then simply search for the blueReader under “Bluetooth Scan” and wait until the first values arrive. If necessary, select “Start sensor” in the main menu and enter a calibration value.

For iOS I will publish in the next days more Information.


Number One…

Without to much words:

The package list for the first has been completed!


and labeled with the all you can eat label package  🙂

The first boxes will start the journey tomorrow to Germany, Switzerland, Slovakia and to England! I also hope that I get the order system adjusted today to send the tracking codes to the first customers!

What is in the box?

1x blueReader colored as ordered (and with or without magnets)

1x wireless Charger, in the ordered color

1x Micro-USB-Kabel if chosen

1x Short manual in german and english: blueReader short manual

1x Holder v3: same color as the wireless charger.

I hope this increases still a little more the anticipation 🙂

MIstakes found…

A week search is now behind me, but I have found crucial errors.

Now the delivery is close!

What was going on this time?

  • Saving energy on the edge of the game has a massive impact on the stability of the chip.
  • There are many possibilities to realize uart communication on the chip, but apparently only one that really works.

The result is a much slimmer and faster firmware which unfortunately needs more energy as I had hoped (in comparison to the last post), but still low enough to have probably energy for up to 7 days. The energy levels of this one measurement described in the last post could not be reached again, unfortunately. But if the tests are good, and up to 7 days are possible, this is still a very good result in my opinion, especially if the runtime is reproducible.

Now comes the finishing touches for the transfer of the commands and the devices will go into shipping. I will avoid a longer test period, since  the firmware can be renewed at any time via a mobile phone. 🙂

The final sprint is here!

The final Countdown…

…starts now!

Why did I not report back for so long?

Because I’ve worked a lot! But what had to be done?

We have still found one or the other small problem with the hardware and I have started with the final firmware for the blueReader. There was also one or the other problem with the software and many small surprises:

Most of the headaches had always been the energy consumption, so we measured, tweaked and tried out to find out where the whole energy went, although we still use one of the most energy-efficient chips available on the market (The nRF52 is of course much better, but was not yet available at the start of the project).

The answer was not so easy, we first decomposed the hardware step by step (or equipped boards only partially) to determine the real consumption of individual components.

This brought only a small improvement: A redundant diode could be deleted from the placement plan and brought us minimal more energy when loading the blueReader, but nothing that is of real significance.

So I have continued with the software. Where can energy be wasted? A few minor things are noticeable, as on page 41 of the reference documentation of the NFC chip, a footnote to a table describing a function that simply is missing in the documentation of the protocol and helps saving a lot of energy. These and many other minor changes brought me to a stable runtime of two days with one load.

That was still not in the range of what I wanted or regarded as something acceptable. After this, an odyssey lasting over a week started with me versus the internals of the BLE chip …

After a short time, it was clear that a mistake in the management of the connection between BLE and NFC chip caused a far too much energy need for nothing, and even more because it was sometimes the reason because of which the NFC chip was not sleeping. Result: over 3 days running time are possible. However, during those tests there were always errors in the timers, which are code blocks which are executed after a certain time or at certain intervals. This took me eventually to the finish line …

After devouring incredible amounts of documentation on the subject of the timer, I was able to re-structure the code and went expectantly into the initial measurements:

For all those who only see a colorful picture: This is a measuring device, actually a quite expensive one, but this one is self built by us 🙂 For all others: A measurement with a 10Ohm shunt, resolution 20ms / 0.1V, large plateau is read out of the Libre-Sensor, small plateau transfer of the data to the mobile phone, tail is standby with active BLE connection …

The energy requirement is now negligible! Negligible? Yes! The system should now run over 25 days with just one load: D But I will not wait until it is empty before I deliver the first devices … But I will write a post of course as soon as I have the first reliable data!

If the calculation should coincide with the reality, it is enough to charge the blueReader during the warmup time of a new sensor to get enough energy for the next 14 days, but as I said, first wait for data!

Oh so, the data also refer to some changed parameters.. so far, all solutions have read the sensor at top every 5 minutes, but the sensor itself stores a new value every minute! So I have reduced the interval to one minute for these tests and calculations 🙂

What’s up next?

  • A few small changes are still necessary in the firmware to be able to deliver the first devices.
  • These changes I intend to have completed by Monday.
  • Here are now waiting almost 20 devices to get their release firmware (all transparent, with and without magnets) which are then to be sent directly to you all  🙂

So let’s see if this weekend brings even more joyful surprises!

View of the work…

First a small look at the desk:

A debugger for the chargers is one of the latest achievements that the 3D printer has printed for me.

But why a debugger for the chargers?

The chargers also have a very small microprocessor to generate the oscillation for the charging field and to control the LEDs. And they do have an interface which enables me to look at charging process and to determine if that board and blueReader are matching. Tiny variations in the tilt of the charger and receiver coil can have a huge impact on the charging process.

In the background you can see the first batch of blueReaders currently being tested for more unexpected hiccups.

Meanwhile, even the assembly of the blueReader has got revision numbers and we are already at version 31 of the instructions to build a finished blueReader, starting with the board.

The last important changes were:

  • Pre-encapsulation of the batteries to avoid air bubbles on the side which can arise from the protective electronics.
  • The soaking of the board in cold (thus non-hardening) silicone before the actual pouring to get the air out from under the components and especially under the shield of the Bluetooth module.
  • The gluing and laminating of the antenna to avoid breaking.
  • Use a silicone adhesive to connect the antenna to the battery, the battery to the board and the charging antenna to the board.
  • Adding another blot of silicone adhesive on the opposite side of the loading antenna to prevent the board from sinking one-sidedly.
  • Replacing the charging antenna against a much larger one without increasing the size of the blueReader.
  • The pre-coating of the magnets with an adhesive base for the silicone to avoid a detached silicone layer over the magnet.
  • The punching of the antenna to achieve a better connection of the silicone layers.
  • Minor changes in the electronic parts which lead to a lower power consumption and easier assembly of the board.

This list can be made at least twice as long and omits the developed tools, forms and components, or the list of the added test procedures. The complete list, the construction manuals, the molds and tools will be published anyway! So a little more patience for those who are interested.

At the moment, there are daily conversations between my engineer and myself to avoid any further problems. But the tests so far are very promising and we continue the production and testing until further notice. Currently our capacity is about 5-10 devices per day. Unfortunately this is depends very much on the amount of bubbles in the silicone, how long and frequently this must be vacuumed that al less bubbles es possible are put into the blueReader.

Finally, the tension is relieved, now we focus on production and verification!




What’s wrong with us?

Where are the devices?

We were stopped. The first devices came from the production and were tested by me…

The result: many broken blueReader :/

  • blueReader can be frozen, but not too deep, otherwise the battery will suffer permanent damage.
  • blueReader can be baked, but also not too hot.
  • blueReader can be folded, but that destroyed it.

What they can be destroyed by folding? What happens there???

Unfortunately, the paths of the antenna break as soon as the blueReader are folded to much.

The last days we have therefore intensively researched, tested and tweaked the blueReader’s design. The result is a packaged antenna and a slightly modified design:
In addition, we were able to significantly improve the charging system and provide more energy in a shorter time.
The new antenna design now consists of a laminate of two plastic films and a stiffening layer of plastic around the antenna. In addition, the design of the silicone hull has been slightly modified to exert less pressure on the antennas traces.

But what about the freezing and baking? To look at the safe operation parameters of the blueReader I’ve put several in the fridge and into the ice compartment, two into boiling water and several into oven at different temperatures.

The result:

  • At about 60° Celsius the battery starts overheating and puffs up.
  • At about 70° Celsius this state becomes irrevisble and the battery loses its power.
  • Below 10° Celsius the battery loses its power really fast (Energy gets converted to heat).
  • Below 0° Celsius the battery starts to freeze and loses most of its power.
  • Below about -10° Celsius the battery dies and can’t be recharged any more.

Under no circumstance I have so far managed to destroy the battery in a way that it broke up in flames or leaked  🙂

What is next?

Currently the new molds are being built and the blueReader, which have so far been cast, are being equipped with new batteries and improved antennas. Hopefully we can test them in the next days 🙂

Forward, backward, upwards!

It continues…

A few new attempts for a holder for the night or sport are finished and almost all have missed the mark… Still the pile is not as big as with the charger cases.

Finally, one good result was finished in the end: In comparison again to the best prototype so far:And on my arm: After one night is the best one I have done so far. The sensor is not under pressure, but the blueReader is also safely kept in place, even against the evil forces of the bedspread and turning around. One of the first long nights (with turning around 5 times around in the bed) where no alarm came because of missed values!

Also the production of the housing goes ahead: One housing after another falls out of mold and after Easter it will have the first completely finished chargers.

With the rest, I’m still waiting for parts again, but after Easter it should go on there too! Currently over 100 blueReaders are in the different production steps 🙂

Another update…

Today a little more relaxed update from me…

Now that the ordering system is online and I have cleared many big and small things, it goes on with fresh strength!
Only 28 coupons are not used yet!

Currently, about 100 blueReader are in production and will be shipped in the next few weeks. As soon as we have a device ready, and it has passed all tests, an email will be sent to the recipient that their order is now processed and thus can not be changed. Until then, you can decide as often as you like, the coupon key is tracked through orders and cancellations!

The charger has also a few news: Since I was just preparing new molds, I came up with the idea of ​​not printing in plastic but wood … Well not real wood, but wood filament which reminds more of pressboard than of wood, but it smells good:  At first sight it looks not so great, but you can grind it and fill with wood glue 🙂

The final prototype made of plastic generated this result:
especially on the inside it looks quite rough.

The wooden mold with wood glue smoothed and polished: 

Already better, but also not quite the maximum…

But wood can be painted, much better than the printed plastic: now the sides cast reflections too and it finally looks as I imagined. Even the silicone shape makes a completely different impression:

The only pity: I already had about 40 cases prepared, but they go now into the garbage, the new cases are just so much nicer and the expenditure for the production of the housing is also not so high (stir, pour, wait, demold)!

It took me a long time…

It took much too long to my taste, but now all coupons are send to the supporter!

Please check if you got your key and if not, please contact me with your full name and the email address where you registered with startnext at

The first devices are now in production and we hope to get about 80 devices ready before Easter and get them into shipping. Then my engineer will have 2 weeks of holiday … this seems necessary 🙂

The stone…

…which blocked my way for long enough is finally rolling!

Because of the two companies and the amount of unfinished tasks in both I have suffered considerably under burn out in the last weeks :/

But now I have progressed on many tasks and here we go again!

The order page is available now 😀

You can now pre-order blueReader at ! All participants in the Crowdfunding campaign will get their keys starting tomorrow to order their devices!

The allocation will be made according to a very simple principle:

  1. First the supporters get the devices they order.
  2. If one variety is available in excess, the pre-orders get the possibility to buy the blueReaders.
  3. Every blueReader costs 225 EUR, including shipping and taxes.

So much for today, tomorrow is all about the keys and later I have more details about the software, apps and all the rest 🙂