# Voltix Probe

Programming battery-free devices is tricky. The power from a harvester is generally insufficient to support programming. Furthermore, the additional current consumption and the leakage through the programming pins can interfere with the behavior of a battery-free device. But connecting the device to a constant power supply prevents observing its *real* behavior. For many years, our solution to this problem was to attach the device to a power supply and programmer, flash the software, remove the power supply and the programmer, test the new firmware, connect the wires again and so on. This is inconvenient and frustrating when you're chasing a bug.

With the Voltix Probe the process becomes much easier: When programming/debugging is requested, the Probe automatically switches on a constant power supply and supplies the microcontrollers on the Voltix Module throughout the transfer. After programming, the power supply as well as the programming pins are automatically disconnected from the Voltix Module with analog switches. The device returns to harvesting operation and you can immediately observe the new software without interference from the programming dongle.

The Voltix Probe supports programming both, the MSP430 and the nRF52 on the Voltix Module after you've soldered it onto your PCB or plugged it into a breadboard. It has a standard, 10-pin, 0.1-inch connector and is compatible with Tag-Connect cables that support in-circuit debugging.

Additionally, the Voltix Probe has four GPIOs that can be controlled via USB from the CLI or API interfaces. This allows, for example, building test jigs to automatically program and test your Voltix-based devices.

## Features & Specifications

- Custom debug probe for in-circuit programming and debugging of Voltix Modules
- USB Type-C connector for communicating with a computer
- Raspberry Pi RP2040 controller handles programming and debugging
- CMSIS-DAP compatible for programming the Voltix Module via pyOCD or OpenOCD
- Makes UART output from Voltix module available via USB

## Software

The [Voltix Probe software](https://github.com/VoltixTeam/Voltix_ProbeSoftware) consists of two parts:
The *firmware* is running on the RP2040 on-board the Voltix Probe and exposes a USB interface for interfacing with the Voltix Module via UART, ARM SWD and TI SBW.
The *Python package* runs on a computer and offers a CLI and API that talks to the Voltix Probe over USB.

For installation and usage instructions, refer to the [repository's readme](https://github.com/VoltixTeam/Voltix_ProbeSoftware).

## Pinout

![Probe Pinout](./img/voltix-probe-pinout.svg)

## Pin Description

| Pin       |                                                                                 |
|-----------|---------------------------------------------------------------------------------|
| Gpio0     | General purpose Input/Output. Can be controlled via CLI/API.                    |
| Gpio1     | General purpose Input/Output. Can be controlled via CLI/API.                    |
| Gpio2     | General purpose Input/Output. Can be controlled via CLI/API.                    |
| Gpio3     | General purpose Input/Output. Can be controlled via CLI/API.                    |
| UartTx    | UART data sent from a PC via USB to the Voltix device. Not yet implemented.     |
| UartRx    | UART data sent from the Voltix device to a computer.                            |
| SwdClk    | ARM Serial Wire Debug Clock for programming nRF52 on the Voltix Module.         |
| SwdIO     | ARM Serial Wire Debug I/O for programming nRF52 on the Voltix Module.           |
| SbwClk    | TI Spy-bi-wire Clock for programming MSP430FR on the Voltix Module.             |
| SbwIO     | TI Spy-bi-wire I/O for programming MSP430FR on the Voltix Module.               |
| +3V3      | Auxiliary +3.3V power supply.                                                   |
| VccTarget | Target power supply. Enabled during programming. Can be controlled via CLI/API. |

(constant_power_supply)=
## Constant Power Supply

The Voltix Probe automatically switches on a constant 2V power supply on the *VccTarget* pin when programming/debugging one of the microcontrollers on the Voltix Module.
You can also permanently enable this constant power supply with

```bash
voltix-probe target-power --on
```

The constant power supply remains enabled while the probe is powered or until it is disabled with

```bash
voltix-probe target-power --off
```

## Resources
 - [Schematics](https://voltix-docs.vercel.app/artifacts/probe_hardware/latest/schematics.pdf)
 - [Layout](https://voltix-docs.vercel.app/artifacts/probe_hardware/latest/pcb.pdf)
 - [Assembly plan](https://voltix-docs.vercel.app/artifacts/probe_hardware/latest/assembly.pdf)
 - [3D rendering](https://voltix-docs.vercel.app/artifacts/probe_hardware/latest/3drendering.png)
 - [Software](https://github.com/VoltixTeam/Voltix_ProbeSoftware)