User Manual

There are two primary ways to power the Metro:

Through the Micro USB port up at the top left

Through the DC jack at the bottom left

The MicroUSB jack provides 5V at 500mA or so, there is a fuse that will shut off temporarily when more than 1000mA

is drawn, this is to protect a computer USB port. You can plug this into any computer or USB charger with a USB cable.

You can draw up to 500mA between the Vin, 5V and 3.3V supplies (combined).

The DC Jack is a 5.5mm/2.1mm center-positive DC connector, which is the most common available. Provide about 6V-

12V here to power the Metro. There is no fuse on this connection so you can draw more current, up to 800mA between

the 5V and 3.3V supplies, and 2A from Vin.

Onboard regulators take the USB or DC power and linearly convert it to 3.3V and 5V:

3V - this is the output from the 3.3V regulator, it can supply 500mA peak

5V - this is the output from the 5V regulator (when DC jack is used), or from USB. It can supply ~500mA peak

from USB and ~800mA peak from DC

GND - this is the common ground for all power and logic

Vin - this is the

higher

of the DC jack or USB voltage. So if the DC jack is plugged in and 9V, Vin is 9V. If only

USB connected, this will be 5V.

There is also an on/off switch. This switch is only for the DC jack and does not affect powering via USB

ESP32 WiFi Co-Processor

The WiFi capability uses an Espressif ESP32 Wi-Fi coprocessor with TLS/SSL support built-in.

The ESP32 uses the main SPI port for data, and also uses a CS pin ( board.ESP_CS or Arduino SPIWIFI_SS or 36 ),

Ready/Busy pin ( board.ESP_BUSY or Arduino SPIWIFI_ACK or 37 ), and reset pin ( board.ESP_RESET or