The Problem

This was for a California based vendor of smart energy meters, that would communicate the meter reading to apartment owners on a small LCD display. The information presented was cumulative electricity consumption on a daily, weekly and monthly basis.

The Solution

We participated in the design of the overall system architecture and development of the firmware along with the tools for deployment & monitoring. The electronics in the meters were redesigned on a small footprint board while integrating an IEEE 802.15.4 radio modem chip TI. The radio spectrum of 2.4 GHz was chosen as the spectrum of choice since this was unlicensed around the world and enabled the product to be sold globally with few modifications. One of the constraints was that the entire system would be installed by electricians with little understanding of RF behavior. A deployment and monitoring tool was considered critical to be able to sell these systems to end clients.

The firmware was developed on MSP430 processor. The system was designed to be robust against single and multi-node failures, rogue nodes and interference from other home appliances. The complete application protocol was designed to withstand lost, delayed and out of order packets. The communications were secure using the protocol’s specified encryption techniques. The nodes were designed to switch channels if a particular channel became too noisy to operate.

The code was crunched to fit into the code space of the processor. A Monitoring protocol was built to collect network statistics from each node and to check on the health of the node. A test mode was setup for deployment and commissioning, where the nodes would send data every 5 seconds. The firmware was developed on C, using a layered approach of hardware abstraction, MAC layers, network layers and application layers built as tasks over a custom-built real time scheduler on the IAR development environment.

Along with firmware, tools were developed which helped technicians to easily install, test and monitor the network. These tools were built on the Windows platform. A laptop PC augmented with a radio modem, running this tool would receive test packets from all the nodes that were in the network. The nodes conveyed network statistics such as number of packets received, transmitted, number of child nodes, identity of the parent nodes, history of firmware crashes, network outages, packet errors, channel used, channels switched etc. The user can see a graphical view of the tree of nodes on the laptop. Each node would display the statistics, if a node missed a heart beat packet, this would be immediately highlighted. The user can put the entire network in test mode for faster tracking of problematic nodes.

A complete solution was thus designed and developed from concept to pilot deployment.