Low Latency Switch Case Study: FPGA for MedTech

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The low-latency switch challenge

A medical equipment developer needed multiple Ethernet streams over one specialised optical fiber. The fiber carries a single wavelength, so wavelength multiplexing was off the table.
The device needed a configurable multi-Gbit optical link, a 10G/5G/2.5G Ethernet connection, two 1Gbit connections, and industrial 100Mbit EtherCAT. The EtherCAT link had to stay under one microsecond end to end.
A custom ASIC would have solved it, but not at a viable cost. So the design had to run on off-the-shelf parts, at extreme bandwidth, with zero margin for overhead.

The approach

We built three prototype pairs for the low-latency switch with Demcon, using standard FPGA, Ethernet switching and microcontroller kits. Nothing exotic, and nothing custom-fabricated. That is what kept it affordable.
The multiplexing logic combines packet switching and circuit switching. Packet switching handles the bulk traffic. Circuit switching guarantees the EtherCAT link its deadline.
We optimised at every level that touches the datapath: the Ethernet layers, the FIFOs, and transceiver control. Because latency accumulates in each of them.

The results

All four connections run over the single fiber, multiplexed in FPGA firmware.
The EtherCAT link also holds its sub-microsecond budget end to end, on off-the-shelf silicon.
The low-latency switch prototypes worked. So the project now moves on to a custom PCB and a smaller FPGA. The targets are size and unit cost.

What's next for the low-latency switch?

With the prototype demonstrating the viability of the FPGA-based solution, the next step will be the development of a custom PCB, and porting the FPGA firmware to a smaller FPGA. These steps are required to meet the target size and unit cost of the final product.

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Why QBayLogic?

In order to achieve the lowest possible latency, crucial for the application, a system level design approach was needed in order for the FPGA and Ethernet PHY chips to work in unison. The experts at QBayLogic have the expertise, from system-level to low-level digital design to tackle these problems, resulting in an optimal FPGA solution. Applications where the applied expertise would also fit: