LoMesh is part of the Microchip Get Launched design program, using this central CPU and this DC-DC converter.

Operating over the 915 MHz, license-free Industrial, Scientific and Medical (ISM) bands, LoMesh leverages the spread-spectrum modulation of LoRa® to achieve reliable, long-range, high-sensitivity communication—over a multi-hop mesh—even when faced with significant RF or physical interference. You can use basic AT commands or a MODBUS register map to configure and control its complete wireless mesh stack. This combination of simplicity and flexibility is key to reducing development and deployment times for projects that depend on robust communication in harsh environments.

LoMesh’s modem—which, thanks to its RS485 interface, can talk to any device with a serial port—will arrive factory-provisioned for guaranteed out-of-the-box connectivity but with full support for custom configurations. Whether you are designing an Internet of Things (IoT) product, constructing a smart home, rolling out a sensor network, developing a building-automation solution, or just trying to make your machines talk to one another (and to the SCADA systems that manage them), LoMesh will help you avoid many of the usual pitfalls.

Making Itself Heard

RF communication in industrial environments can be quite challenging. Noise-generating equipment and obstructions like metal machinery limit the range of RF signals, which makes communication unreliable. That, in turn, has led to to the proliferation of overpriced solutions that attempt to compensate for interference through the over-provisioning of costly hardware such as GSM gateways.

With its high penetration power and multi-path immunity, the best-in-class LoRa® modulation of LoMesh’s physical signaling layer has proven itself to be a more cost-effective way to overcome these same challenges. At the end of the day, LoRa® signals just travel further than those of alternative technologies—like sub-gig Zigbee, BLE, and other modulation techniques such as GFSK—without deteriorating into noise.

The Mesh Appeal

LoRa® itself is just a physical signaling layer and not a complete communication stack. LoRaWAN™ is the industry standard that implements a star network over LoRa®. Unfortunately, star networks do not allow for packet hopping and end-point devices must connect directly to a gateway. If one cannot do so reliably, other LoRa® devices have no way to help the device in question, so the only solution is to add more gateways.

By implementing a self-forming, self-healing, multi-hop mesh stack over LoRa®, LoMesh allows nodes to help route data packets between devices that would otherwise be outside of one another’s RF range. In this way, data can be routed from all devices to a central node, which can then pass it along to a gateway for local or cloud-based processing.

Easy to Use

Users of LoMesh do not need to be wireless networking engineers, nor do they require expertise in LoRa® or mesh routing. With just a basic idea of how machine-to-machine communication works, users can quickly configure their radios using serial AT commands or by way of the MODBUS RTU protocol. A host-like a PLC can be connected to LoMesh, over RS485, and can send custom data to other devices in the network via simple serial communication.

Dynamic Sink Node

Every telemetry system has a "sink node" that collects data from the various end-point nodes. For most technologies, this needs to be determined when the system is designed—or, at best, when a particular deployment is configured. For example, every node in a Wi-Fi network must be told where it can find the access point. LoMesh, by contrast, includes support for a dynamically-determined sink node. At any given time, any one node in the system can ask all of the other nodes to send it all data meant for the sink. This opens up a number of new possibilities, none of which requires on-the-fly reconfiguration. Examples include:

• A commissionless data sink configuration, in which the host has the ability to direct a radio to request that other nodes in the mesh begin treating it as a sink
• An active-standby data sink configuration, in which the primary sink can stop sending periodic set-sink beacons, which allows a secondary sink to request that other nodes in the mesh begin treating it as a sink.

Features

• Multi-hop mesh stack
• Devices can be assigned to different virtual networks
• Support for simple AT commands
• Support for a MODBUS Remote Terminal Unit (RTU) profile
• RS485 serial interface
• Repeater functionality is field-configurable via IO pin
• Excellent interference immunity
• Unicast, multicast, and broadcast messaging
• Dynamic sink node setting for gateway devices
• Device Firmware Upgrade (DFU) over UART
• Hardware capable for OTA

Technical Specifications

• 915 MHz ISM-band operation
• 4.5 V to 30 V operating voltage
• Operating temperature from -20° C to 85° C
• Adjustable output power up to +17 dBm
• Receiver sensitivity down to −120 dBm at SF 8
• AES-128 CBC packet encryption
• MUI-64 modem identity

Comparisons

Support & Documentation

The LoMesh documentation currently includes a user manual, a list of MODBUS registers, and an AT command set. Our GitHub repo includes source code for the module, and open source Windows applications that allow you to issue AT commands and configure MODBUS. You can also reach us through the Ask a technical question form on our campaign page.

Manufacturing Plan

LoMesh fabrication and assembly will be handled by AllPCB in China. They will also test the boards in accordance with a plan we are developing. We have worked with AllPCB in the past—including on LoMesh prototypes—and are confident that manufacturing will go smoothly.

Fulfillment & Logistics

To avoid violating the RF-spectrum policies of various national regulatory bodies around the world, we will only be able to ship LoMesh within the United States. When it comes time to do so, we will ship all crowdfunded products to Mouser Electronics, from which they will be distributed to backers. See Crowd Supply’s article on Ordering, Paying, Shipping: The Details for more information.

Risks & Challenges

The greatest risk we have faced so far has had to do with certification. Our radio is certified for intentional radiation in the US market, but it is not yet certified in Canada, for example, and we do not currently see a path to certification in Europe. Past experience in this area has made us wary, so we are looking very closely at unintentional radiation requirements in the US while simultaneously exploring the possibility for (eventual) certification in Europe and elsewhere. By way of mitigation, we have identified a number of components on the LoMesh board that we can modify, if necessary, to address any intentional radiation issues that might come up.

Beyond that, we face the same availability risks as any other manufacturing project. Low in-stock quantities and long lead times are always a possibility, though we have already begun working with vendors to reduce the likelihood of parts-related delays.

LoRa® and LoRaWAN™ are trademarks of Semtech Corporation or its subsidiaries.