openLibreReader and status

openLibreReader und Status

today , finally new updates ūüôā

Production is now in full swing again after we were overrun at the beginning of December by the DHL strike followed by the Christmas chaos :/

In the next days I will ship the last orders from December and invite more  pre-orders to checkout.

As some have already noted, the openLibreReader app is about to expire, but a new one is already available from Apple and is already waiting more than 2 days for a review.
Before I was able to translate from the german text, i got the mail confirmation that the app has been reviewed and everybody can now update to version 1.0.2.
Please don’t be scared, the version has a bug and no longer displays a TodayWidget. The bugfix is ‚Äč‚Äčalso already for review at Apple, but I have not yet put it into the review to get the current review as fast as possible to TestFlight and I have already committed it to the review process.

What comes with the new version?

Simple AppleWatch support

  • Simple AppleWatch support
    This one is not great yet, but I can not test it myself, as I do not have an AppleWatch yet (please continue to donate a ) .
  • New calibration: linear regression
    Now you can enter the slope and the intersection for an adjustment of the values.
  • Improved reconnect
    The app should now reconnect more reliably to the blueReader or a LimiTTer, if the connection was lost.
  • Improvements in translation.

For all those interested in DIY, all sources are also available at There, the build errors have been fixed and now all needed pods have been added to the repository.

A big thank you goes to the user GerritR for the calibration and the watch support! And of course to all testers who have given me feedback (none of it is lost, I will add your suggestions gradually!).

Also a huge thank you to, Masterplexus, who does not only help voluntarily here in the Support Forum, but has also done a lot of great things with xDrip+. In the current nightly builds you get a much better support and the correct battery indicator for the blueReader, too ūüôā


  1. If the App shows a white page once you click on a calibration, please close the app (double tap homebutton and slide it out), restart app and it should work again. Will be fixed with the next update.
  2. The font on the watchApp might be to big for mg/dl display.
  3. Add SweetReader support

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. ūüôā

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 ūüôā 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 ūüôā

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 ¬†ūüôā

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!


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 ūüôā

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¬†ūüôā

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¬†ūüėÄ

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 ūüôā


A small update to the current status:

  1. The start of the production is almost finished ūüôāAt the moment, I produce housing parts and blanks for casting molds so that we can now pour very quickly a larger quantity of devices.Every 20 minutes one housing and two forms are finished.
  2. I have made progress on the attachment
    This is¬†the result¬†ūüôā Currently we try¬†with silicone waste¬†whether it works better from plastic or silicone. As soon as we are¬†able to make a decision, I will¬†show the different variants and what we think is the best solution.
  3. Magnets The first devices with magnets have gone into the test. Everything works great, but the devices are about 1mm thicker than the devices without magnets. It is strong enough to handle most everyday situations, but you can easily loose it while handling a backpack or by turning in your bed.
  4. I am currently working on the order system with high pressure
    It should have been online since the weekend, but I also underestimated this task…

What is next?

Once the order page is online, all supporters of the Crowdfunding Campaign will be able to order their blueReader. First the one who ordered prototypes and then the people who ordered series devices.

Every person can freely choose whether they prefer a series or prototype blueReader (or mixed, if you have paid for several).

In addition, the rest has the possibility to pre-register for devices. This is not a binding purchase! Once the requested devices are ready, you will be given the option to pay them via the website (via PayPal).

The countdown ticks…

Finally, here are the newest information about the blueReader:

  1. We are working on the final details of the production…
    1. The colors have finally arrived:You can choose between beige/skin color, blue, green, red, black or natura/transparent for your Device!
    2. The charging electronics is in production, maybe I have the first charger tomorrow and can show you how it looks and works…
    3. We are diligent in improving the design in order to make a simple and safe production possible: Casting trial in an open-top silicone mold, unfortunately not the desired result, as the silicone bulges at the edges. In addition, too little skin color¬†pigment ūüôāNew form refinements, based on the first attempts ‚Ķ
      Evolution of forms and materials used ūüôā
    4. Also the charger will be available in different colors, however, as usual the¬†casting stuff is stuck somewhere‚Ķ Hopefully I can also show first versions of the final charger¬†in the coming days¬†and what¬†colors will be available¬†ūüôā
  2. So far there was unfortunately no feedback on the design¬†:/ Before the publication of the dimension data and 123Design, as well as openSCAD files, there were regular¬†commentsregarding the design.. Perhaps it was because of the tools I¬†used‚Ķ So here’s the current design, this time as a¬†Fusion 360 project:¬†Link to Fusion 360 Projekt¬†

    In addition to the sketches for the board, the battery and antenna, and the current design and the build platform required for the assembly is also contained in the Project: 
  3. How can you then choose which color the blueReader should have and which color the charger? Once we have produced the first units, all supporters will receive a coupon code and a link. On the webpage you can verify and correct your shipping data (Not that anything has been wrongly taken from Startnext) and choose your Device(s)!

I hope to provide new information soon!


A new Year…

… and hopefully a happy one ūüôā

It goes on! After another, unplanned timeout, through a violent flu right on time for¬†Christmas, I’m back on the legs and working.

Where do we start?
With a few pictures ūüôā

A series of prototypes. On the far right the 0.2.0 prototype i have worn in December, still with thick battery right next to the board and the additional charger on top of it. In the middle my development slave 0.2.1. This poor one had to go through a lot a software versions (today I finished version 84 of the blueReader firmware, before that there were many versions of blinkie and uartie firmwares for the basic function tests and optimizations). Next to it, on the left, the same prototype, but with a battery, which I currently carry on my arm.

This has already the final size, but will probably be¬†marginal (about 1mm) thinner. What is still missing is currently the coil for the wireless charger. Those¬†still hang in the customs and are¬†supposed to finally arrive this week …

It also makes a very good impression on¬†the arm, for me at least ūüôā

But how does it hang there?

These two neodymium magnets hold the blueReader perfectly in position and also keep it safely during most everyday situations. Cuddling, dog, pulling on and out sweaters and strong turning in the bed can still carry him off the arm. Therefore, almost perfect ūüôā The small magnet is simply fixed with a piece of insulating tape from the hardware store on the Libre, the large one between two layers Leukosilk. In any case, you should pay attention that the magnets do not come into direct contact with the skin, since the usual neodymium magnets are nickel-containing !!!

How is it going now?

  1. Potting tests:
    Because of the missing coils we have been waiting with the potting, but hope to have first results by the end of this week.
  2. Software:
    With version 84 in the basic firmware I think i have now reached the necessary stability to be finally able to start with the libBlueReader. Almost all aspects of the firmware were tested in the last few weeks and were once again reworked, counter-tested and some¬†discarded and re-developed from scratch. Although the current version has only about 3000 lines of program code, each of these lineshas to be perfect, as¬†I absolutely want to avoid that there are problems in the basic functions later, such as the encryption of the connection, or the update function. All “higher” functions can be corrected later in the event of errors by software-updates.

The goal to be able to send the first series to all supporters in January comes into sight now¬†¬†ūüôā