If you purchased an UrsaLeo RPi DevKit, you can request this debug LED module at no charge by submitting a request here: Submit a request
The UrsaLeo RPi debug LED module is a simple RPi plug-in module that provides three functions:
- LEDs: to indicated status and connectivity of the UrsaLeo RPi Gateway
- Serial Console: A connector for connecting your PC to a serial console port
- Switch: A switch (SW3) for initiating an orderly shutdown process
Debug LED module Installation
- Make sure power is off
- Visually line up the corner screw hole with the screw on the RPi. This is the hole next to the expansion connector (the 2 x 20, 0.1 pitch male header).
- Plug the debug LED module into the header. It should line up with all 2 x 20 pins. The screw is optional but can provide mechanical support for the switches. The screw hole is metric (M2.5). Either use appropriate washers (fiber) to avoid shorts or use a nylon screw/nut.
Debug LED module Operation
As the RPi is booting, LEDs 1, 2 and 3 will turn on as follows:
- LED 1: On (connection to Google IoT Core)
- LED 2: On (connection to Thunderboard Sense 2)
- LED 3: On (authentication with Google Cloud Platform) after a few seconds
- LED 4, 5 and 6: will be off as they are reserved for future use
Note: If LED 2 is not "On", press the reset button located in the center of the Thunderboard to establish a connection.
The debug LED module includes three switches as follows:
- SW1: Reserved for future use
- SW2: Reserved for future use
- SW3: Initiates an orderly shutdown process
Connecting the Serial Console
To connect the RPi console to your laptop use a USB to TTL Serial 3.3V UART Converter Cable (FTDI P/N TTL-232R-3V3). This is a USB to 3.3V UART cable with a 6 pin 0.1" spaced female header. Here are some sample cables:
To connect the RPi console to your laptop, locate connector (SV2) pin 1 on the RPi LED/SC board. It is labeled with a “1”. Locate pin 1 on the cable. There should be a raised triangle/arrow to indicate pin one. Use caution to ensure the cable pin 1 is aligned to the LED board connector pin 1. Line up the female cable pin 1 with the male connector pin 1 and plugin. If the rest of the pins do not line up, check for either bent pins or wrong part number (FTDI also sells a metric flavor of the cable). Connect the USB end of the cable to your laptop.
Your laptop will typically include virtual com port drivers. Run any terminal software and connect.
- For Windows, free terminal software includes: Putty and Tera Term.
- For Linux, you can use: screen, minicom, kermit, etc. The com port settings are: 115200 baud, 8 data bits, 1 stop bit, no parity, Xon/Xoff.
Gain Terminal access to your UrsaLeo Gateway DevKit
- Download and install Silicon Labs VCP drivers on PC (Windows or macOS): Silicon Labs VCP drivers
For Windows PC:
- Download and install Putty serial comms software on PC:
- Start Putty and configure serial settings:
- Baud rate: 115200
- Data bits: 8
- Stop bits: 1
- Parity: None
- Power on the DevKit and wait for the boot prompt to appear
- Launch Terminal.
- Connect to the USB serial port. ls /dev/tty
- Set the port to 115200 8n1. No flow control.
- sudo screen /dev/tty.SLAB_USBtoUART 115200/8/1/n/Xoff
- Enter your admin password for the macOS user.
- Hit enter until you see prompt for a login.
- Login as “root” with no password
- The shell prompt appears ready to run commands