SYZYGY peripheral firmware provided by Opal Kelly can facilitate power sequencing for peripheral designers. The SYZYGY specification requires that a pod prevent output of any signal to the carrier until the VIO rail has been detected. The recommended MCU includes analog-to-digital converters that can be used to detect valid voltage levels on the VIO, +3.3V, and +5V supplies. Logic outputs from the MCU can be used to enable circuitry on the pod.

A link to the reference firmware can be found in Links and References.

The pod MCU may be pre-programmed before PCB assembly, or it can be programmed in-system. Some distributors such as Digi-Key can provide pre-programmed chips using customer-provided firmware.

Although not required, Opal Kelly recommends including a Tag-Connect pogo-pin style programming header on SYZYGY pods for ease of programming and debug. Tag-Connect does not require a mating connector on the PCB and it uses a minimal amount of area.

An example of the Tag-Connect interface is shown below, circled in red. This footprint accommodates the TC2030-IDC 6-pin interface.

Further information about Tag-Connect can be found here:
https://www.tag-connect.com/