Design review: Processor

[krook]

Evaluate alternatives to the ESP32 currently in use to optimize for better design and energy consumption.

The processor currently being used is esp32 based and leverages the ESP32-WROOM-32 module. The module is embedded on a development kit in the prototype, but this will not be sufficient for an updated production design. Instead directly designing around the ESP32-WROOM-32 module can be evaluated, but this has tradeoffs regarding design appropriateness.

The ESP32-WROOM module includes a number of interfaces that may not be necessary for this design, including Wi-Fi. Wi-Fi existed in a previous version, but has been replaced with a Bluetooth Low Energy component. The necessity for Wi-Fi in this design should be carefully considered, as this is a relatively high power interface that should not be deployed unless required. The average operating current is approximately 80mA and can go up to 500mA, which is higher than necessary for a design that may only need BLE and serial I/O connectivity.

Instead, it is recommended that a processor from the Nordic family is considered, as these modules are leader in the IoT space, especially for BLE. It is still recommended to stay with a module as this will support a faster design and certification cycle. However the module should support automated assembly and should have measures in place for scalability, such as offering a form factor conducive to future drop-in replacement.

A recommended module that meets these criteria would be the Fanstel BT832 or BT840 modules. They are designed as an LGA package with castellated edges, and the two modules, among others, are pin-compatible. The Nordic line of processors are also designed to support extremely low power operation.