TRXnnn-72: New modern LoRa radio module

Transceivermodul TRX433-72

Why we are developing a LoRa radio module

For 30 years, we have been offering our customers various radio solutions in the form of radio modules and also as circuits integrated directly into the PCB layout. As radio technology has constantly evolved during this time, we have also been able to continuously improve and optimize our radio solutions . Starting with discrete AM receiver or transmitter stages through to the latest modern GFSK or LoRa radio IC solutions. Each new radio technology promises an improvement, such as more range, less power consumption, more robust against radio interference or new networking options. How well the manufacturer's promises can actually be achieved outside of optimum laboratory conditions can usually only be clarified through extensive measurements with specific wireless measuring devices and additional field tests. To save our customers this time-consuming work, we have developed the flexible TRXnnn-72 LoRa radio module . The radio module uses the latest generation of LoRa transceivers from Semtech. With an additionally developed evaluation kit , the radio module can now also be tested very easily by the customer directly on site with a wide variety of configurations.

What are the advantages of the radio modules from Schmidiger GmbH?

As an SME interested in long-term customer relationships, our product strategy is fully geared towards our customers. The use of our radio modules therefore offers a number of advantages over modules from other manufacturers.

• We can develop a radio module precisely according to the customer's requirements and also fulfill customer-specific wishes.
• We can enable customer-specific modifications even for small quantities.
• We can guarantee a long product life cycle for every radio module. If a module is discontinued, we offer the affected customers a suitable alternative.
• We can guarantee that a radio module is not suddenly modified , which would result in a new or further development for our customers.
• We offer everything from a single source, from development to production, which means we can react very flexibly to requests or problems.
• For maximum radio range, we also offer support with antenna optimization.
• Even after development has been completed, we continue to offer our customers support in the event of any problems during use.

Selection of the radio IC

Modern and affordable radio solutions today use integrated circuits, so-called radio ICs, practically without exception. However, as there are now many different manufacturers, the variety of radio ICs on offer has increased dramatically in recent years. Just evaluating the best radio IC at the moment is a major challenge, as it is difficult to compare the technical specifications of the various models on a 1:1 basis. In order to be able to determine which radio technology and which technical features are the right ones for an application, you need to have some basic radio knowledge. Thanks to our many years of experience in radio technology, we are able to evaluate important and less important properties accordingly and thus evaluate the best radio ICs in terms of current technology. In the area of LoRa technology, we have therefore opted for the SX126x radio IC series from Semtech for our radio module.

Measurements with the evaluation kit from the manufacturer

In order to get an initial feel for the newly selected radio IC, the next step was to carry out initial measurements with the manufacturer's evaluation kit. In our example, this was the Evalkit SX1261DVK1BAS for the 868MHz frequency band. These measurements allowed us to check the most important information from the data sheet for the first time. It is not uncommon to find that some of the specifications in the data sheet can only be achieved with very special settings that are unusable for most applications. In general, it can be said that the manufacturer knows all the tricks of his own radio IC and therefore it will hardly be possible to achieve better values with his own radio module than with the evaluation kit from the manufacturer. As there is still no evaluation kit from Semtech for the SX126x series for the 433MHz frequency band, we have also closed this gap with our LoRa project and now offer a 433MHz and 868MHz evaluation kit.

Evaluation kit 4

Hardware development

Once the radio IC had been definitively selected, a schematic and a PCB layout had to be developed for our own radio module. In order to meet all the relevant standards in the end, numerous other components for signal filtering and impedance matching had to be planned in addition to the radio IC. There were also numerous rules for high-frequency and radio IC-specific requirements to be observed during the subsequent layout in order to achieve maximum performance with the module. Normally, the first step in module development is to create a prototype, which has to be revised and optimized again after commissioning. The TRXnnn-72 LoRa radio module does not have its own microcontroller and can be configured and controlled as required via an SPI interface. This means that the module can be used very flexibly for a wide range of applications, includingLoRaWAN. The radio module is available from us in 433MHz and 868MHz versions.

Software development

A software driver that controls the function of the radio IC was essential for commissioning the radio module. This software driver can either be obtained directly from the radio IC manufacturer and adapted accordingly for your own microcontroller or alternatively developed yourself according to the radio IC data sheet. It is particularly during software implementation and commissioning that all the pitfalls, ambiguities or restrictions that are either not mentioned anywhere by the manufacturer or have not even been noticed are revealed. Good contact with the manufacturer is often helpful in finding solutions to the problems as quickly as possible. In our example, we have created our own software driver that can be used for the 433MHz and the 868MHz TRXnnn-72 LoRa radio module. In addition, we have developed software for our own Evalkit4 so that we and our customers can test the radio module with a wide variety of configurations in the simplest possible way.

Commissioning and standard measurements

Now came the all-important measurements during commissioning. With the radio module, the Evalkit4 and the corresponding software driver, all performance measurements could be carried out and compared with the specifications in the data sheet. In addition, numerous standard measurements also had to be carried out to check whether all limit values of the currently valid radio standards were complied with. In this step, the filter stages and also the impedance adjustments often have to be slightly adjusted again so that the maximum performance according to the data sheet can be achieved and all standard measurements can be fulfilled at the same time.

Thanks to the development of the two LoRa radio modules TRX433-72 and TRX868-72, we can now offer our customers two LoRa radio modules that can be used very flexibly for point-to-point radio links as well as for LoRaWAN applications. This has enabled us to massively expand our technical know-how in the LoRa field. We now know the tricks of the trade for integrating this technology into any customer product with maximum performance.

We would be happy to advise you and provide you with a 433MHz or 868MHz evaluation kit for initial trials. We look forward to your inquiry.