Architecture

The Gizmo platform is comprised of several different components. In this section we'll look at the architecture of the software, the hardware, and the interfaces between different components.

You are not required to understand the architecture to be able to use the Gizmo platform. This will not be on the test.

Overall System Architecture

The overall architecture of the Gizmo system composes a control point, the Gizmo itself, and anything hooked up to it. This can be broadly visualized with the diagram below:

OperatorControllerGizmoPeripherals Human controls GamepadUDP Control StreamGizmo Controls Peripherals

Gizmo Hardware Architecture

The hardware architecture is comprised of 2 processors, an I2C link between them. Here's a block diagram of how it all works.

GizmoSerial DeviceSensor or IR emitterPWM Motor ControllerR/C compatible PWM controllerServoHobby ServoLimit SwitchNormally open or normally closed switchNeopixelsProgrammable RGB LEDsSystem ProcessorRuns Gizmo System Software (GSS)User ProcessorRuns User Code I2CAsynchronous SerialHardware PWMHardware PWMGPIOHigh-speed serialSensor or IR emitter R/C compatible PWM controller Hobby Servo Normally open or normally closed switch Programmable RGB LEDs Runs Gizmo System Software (GSS) Runs User Code

The system processor is implemented as a peripheral device that the user processor controls. This allows the user code to be the root node on the I2C bus which dramatically simplies the implementation. The System Processor also supervises a number of different devices on the board including voltage supply rails, battery input voltage, and when the last time the User Processor asked for data was.

Gizmo Software Architecture

The command line gizmo tool is a "multi-call binary" meaning that it can do different things depending on the options you start it up with. You can think of it as a bunch of different programs all contained in the same file which makes it easier to distribute. The same exact gizmo tool is what runs on the Driver's Stations and the FMS. While we make every effort to make compatible updates, in general you'll want to run the same version of the Gizmo utilities everywhere. We note explicitly when backwards compatibility cannot be maintained, so check the patch notes.

Direct Connect

Speaking in terms of time connected, most Gizmos will spend most of their time in what is called "Direct Connect" mode, which forms a direct point-to-point link between the Driver's Station and the Gizmo System Processor. This looks like this visually:

Driver's StationGizmoGamepadGizmo SoftwareDS NetworkSystem ProcessorUser ProcessorEthernetIntegrated Radio USBHost Network StackI2CPoint to Point Link

The control is passed from the gamepad to the Driver's Station via USB, then via wireless link to the Gizmo System Processor, then via I2C to the user processor where these values are consumed by user programs to control a robot.

Field Radio

During a competition, it is imperative that a solid link be maintained between the Gizmo and the Driver's Station. The weak part of this chain is the wireless conection, so to ensure a solid connection, we replace the Driver Station's internal radio with a substantially more powerful external radio wth external antennas. This also ensures that each team is equally affected by any interference, since the central radio talks to all robots on a given field. One field radio per field is required.

The FMS does not process or interact with the control data, it only provides a different means of transfering this control stream from the DS to the Gizmo. Visually, this is the path:

Driver's StationField Management SystemGizmoDS NetworkField BoxScoring BoxFMS WorkstationSystem ProcessorUser ProcessorEthernetIntegrated Radio EthernetEthernetI2CEthernetWireless

The FMS maintains an isolated data-path for each Gizmo/DS pair, and ensures that no robot can interfere with another's control stream. This is why the FMS needs to know where each team is located, so that it can provision the correct access onto the specific Field Box port going to that team.

Observability

Gizmo boards pass statistics information back to the driver's station, which in turn shares them with the FMS. The Gizmo board also reports some metadata information related to things that can prevent the system from working directly to both the Driver's Station and the FMS.

You can use this information to get a better understanding of what's going on with your field and Gizmos. Here are some example questions you can answer using this data:

  • Are all Gizmos connected?
  • Is there persistent interference?
  • Did any team experience a disconnect?
  • What is the battery voltage on all connected Gizmos?

This information is ingested by the metrics module and made available over HTTP as an OpenMetrics compatible metrics stream. Example Prometheus and Grafana configurations are available in the Gizmo repository.