Helium Kerlink Miner iFemToCell

Kerlink Helium Miner iFemToCell

Kerlink is a LoRaWan hardware player since the first ages of this technology. This French company has equipped most of the operator’s network and is used to propose high quality industrial products.

The iFemToCell is not a new product. It exists since a couple of years and I already tested the IFemToCell 4 years ago. Recently the company has created a Helium edition we are going to review in this blog post.

This is an interesting device as it is a kind of hybrid between a light miner and a full miner. Even if the Kerlink platform is powerful, it is far away the power of a raspberry Pi and certain operations like consensus group can’t be performed. As this is now delegated to Validator, this difference have no impact on rewards. In another hand, this device is consuming less power and it is possible to power it with sun more easily. This is quite interesting.

Let see what is this device and what is specific during its deployment.

Hardware specification

At first, I wanted to see the differences between the 2017 iFemToCell device I have at home and the Helium miner version.

Kerlink iFemToCell 2017
Kerlink iFemToCell Helium

At a first look you won’t see any difference between the two … and at a deeper look you won’t see anything interesting. Some references are a bit different, it should be related to part obsolescence or shortage. I was expecting to see a secure element but in fact it was already part of the main MCU and just not activated previously. I was expected the flash memory larger but is still a 8GB memory. The DRAM chip is different, the original version has a 256MB memory and it seems the Helium version also.

As a consequence, this hotspot can’t work the same way on the chain as the other solutions having at least 1GB of memory and 32GB of storage with storage regularly saturating. This is forcing the chain to resync with 1-3 days of unavailability (when no turbo sync has been developed by the miner provider)

Blockchain specificity

As the Kerlink miner have a smaller processing capacity and smaller memory and flash it has to work differently that the other miners. A few month ago is has some operation it was not able to perform on the chain like the Consensus group. Since, these operations has been transferred to validators. As a consequence, the miner performs the same operations as the other miners.

Kerlink seems to have developed a specific software adapted from the Helium source code with a lot of optimization in it. They don’t want to give a lot of details on this to be preserved from competition. One of the main element is to rely on an intensive use of snapshot (also named turbo sync). This approach has been deployed by many different miner provider, like synchrob.it who has the first one to implement it. In a decentralized point of view, this is not a really good way to manage a blockchain but in term of miner performance it is quite good.

The principle is to directly comes to the result of the chain processing instead of processing the blocks one by one to reach the head of it. The snapshot contains all the computation and you just need to load it instead of processing it.

So basically Kerlink miner is getting a recent snapshot and just need to sync a small amount of blocs between the blockchain head and the snapshot head.

As the blockchain db is growing and growing the miner needs to restart a fresh sync on regular basis. With less flash available on Kerlink this processing will have a higher frequency. Thanks to the snapshot based refresh this operation will be short.

On top of this optimization that becomes more and more a standard approach for all miner provider, Kerlink has optimized the code to reduce the memory footprint. Honestly we have seen some memory size issues by the past to process certain blocks and I don’t know if the optimization will bypass all the coming problems. By the way, currently it seems to work well and for the future, the hardware could be converted to light hotspot when available if it has some trouble to process a growing chain. So I’m not really afraid by these potential limitations.

Apparently, this was not optimum and recently, Kerlink has added an external USB-stick to extend the storage up to 72GB (64BG stick + 8GB internal)

The remaining question is about the ability of Kerlink to follow the Helium miner evolution as fast as the other vendors who do not have to repackage the Helium code. This can have an impact during hotfix deployment, something we are used to see on Helium. As the currently running firmware version is not visible with Kerlink it is not something I have been able to measure.

The data consumption is the same as a standard miner with about to 5GB/day currently.

Kerlink iFemToCell registration on Helium

As the hardware has not been made for Helium, there are some feature you usually have on a miner not available on that one. As an example, this miner does not have Bluetooth connection to interact with the application.

Basically it means that the miner configuration is made by the Kerlink back-end servers and you need to manually setup WiFi if you want to use it. So at first you need to setup an Internet connection. The easier way is to connect on Ethernet. If you really need to setup a WiFi connection, you also need to connect first on Ethernet to locally join the miner internal webserver and setup the WiFi. The webserver is accessible on the DHCP given address (so you need to query your router to get it) and the login password is admin / pwd4admin.

As this type of hardware has not been designed for B2C market, honestly the interface, the errors messages or the overall ergonomic is pretty bad if you are not a technician. There is no blocking point for anyone but … It’s more complicated than other brands.

Once you have an Internet connectivity available you can start the installation procedure. This is as usual from the Helium application but you will be route to an external webpage from Kerlink to complete the setup. You need to scan the QR code and type the MAC address manually (Why there is not a second QR Code ?!?) to authenticate your hardware. The MAC address needs to have the “:” separators. Then the registration will be processed.

At the end of the procedure, you have a page like the one on the left. Apparently the QR code is used when you used an external browser and need to link with the phone. It seems you don’t need it and just have to click on the button.

After this, you’re back to the Helium app to setup the miner location and it’s done.

In my specific case, my miner was in a really specific state you should never see. As it was one of the first Miner (even if it has been bought like any regular consumer through calchip) the factory setup was not fully made and the miner has finished its configuration at home. As a consequence,after this sequence, the Kerlink miner has to switch into D.I.S.C.O. mode with led blinking red, flashing for a while… This is a bit the anxious period of the installation. After about an hour, the led will be back green due to the internal watchdog reset and back to normal. So, in case you see the D.I.S.C.O. mode, in fact you just need to cycle it and it will be back to normal. In fact this mode is indicating that the factory setup procedure has completer successfully.

In a normal situation, the miner will display the 3 front leds on and green. The Signification of the 3 different LEDS is the following:

  • LED1 ( on the left – left is power connector side) – RED during boot, GREEN once boot is OK
  • LED2 ( in the middle ) GREEN when application software is started
  • LED3 ( on the right ) blink GREEN when RX data / blink RED when TX Data

Honestly, I would have been really happy to have a LED indicating the syncing status and the P2P connection state more than the LORA TX/RX or software state. Hope that I will be read…

Potential noise

My Kerlink miner also makes a little noise like a tiny hard-drive sound. There is no hard-drive inside the miner. This seems to comes from the WiFi module. Apparently there is not specific problem related with this noise. Kerlink is investigating this point. It could be related with the high level of WiFi transfer but fro real the noise stays here even when using Ethernet. So, according to Kerlink, don’t be afraid by this noise.

Risk of scam

When you open the kerlink box, there is really nothing differentiating a Helium iFemToCell for Helium from a standard iFemToCell, even bought 4 years ago. Even on a box. The only difference is apparently a printed paper added in the box indicating it is Helium compatible. And more recently a specific sticker on the box. As a consequence it is really easy for someone to sell a standard iFemToCell as a Helium miner or a “Helium compatible device”. For this reason you have to be really careful when buying a such miner, it’s only when you will try to register it that you can discover the scam.

This type of business (B2C and Crypto) is new for Kerlink, this is why there is some point to improve in the distribution process like this one. They are working on it.


Now, miners come with an ecosystem like a dashboard to monitor the hotspot status remotely and perform some maintenance actions. There is, currently, nothing like this with Kerlink accessible to the end-user. Only distributors have an access to management tools. You do not have the ability to query anything from the Miner itself like we have over Bluetooth usually. Even the Web dashboard contains no reference about the Helium part. As a consequence you are totally blinded and need to trust the Helium API about your miner status. And we all know that we have to never trust the Helium API status. This should quickly generate a high level of support tickets to the distributors and Kerlink. So I’ll not be surprise to quickly see some tools deployed 😉

From the web dashboard you can check a firmware version only. This one do not seems to be related with the Helium firmware version. There is no SSH access as on other helium hotspot, classical iFemToCell login/pass does not work.

Initial Synchronization

My miner has taken a long time to be synced, it was apparently due to an invalid version of firmware deployed on it. Kerlink has made the update remotely and after this the synchronization has been fast. As a consequence, on a such miner, you should be synced within the day or it means you may have a problem to be reported to support.

I did a resync trial after some days of shutdown to measure the duration and the duration has been about 11 hours. It’s not clear if it is the time to sync from a snapshot (this sounds too much long) or if the snapshot generation frequency is low and it is the time to load it and reach the top of the chain. in this case the duration could vary depending on where you are from the top of the chain. The second time I did a resync, it has been performed in 1-2 hours after a 1 day shutdown. That is correct. The third time was under one hour after a 2 hours shutdown.

Reward performance

I’ll complete this blog post later with my experience on that miner about the reward. I’ll try to switch and existing miner to make a bit of comparison. On one hand, there is a risk of lower reward due to the higher resync frequency and the lake of visibility (every day I have something to do on one of my miner to make it alive again and all the tooling I have helps me to detect this faster and reduce the downtime).

In another hand, the radio performance of a iFemToCell could be higher than a miner running with a noisy (in a radio point of view) Raspberry Pi. The Kerlink could also be deployed in different areas with solar panels powering source witch is a plus (I’ll try to make some power measure later). The documentation is indicating around 3Wh average.

I’ll later update this post with the data I’ve been collected about rewards.

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