# UHD - USRP-B1XX Series Application Notes

Table of Contents

- Specify a non-standard image
- Changing the master clock rate
  - Set 61.44MHz - uses external VCXO
  - Set other rates - uses internal VCO
- Hardware setup notes
  - Front panel LEDs
- Miscellaneous
  - Available Sensors

# Specify a non-standard image

The UHD will automatically select the USRP B-Series images from the installed images package. The image selection can be overridden with the "fpga" and "fw" device address parameters.

Example device address string representations to specify non-standard images:

    fpga=usrp_b100_fpga_firmware.bin

    -- OR --

    fw=usrp_b100_fw_firmware.ihx

# Changing the master clock rate

The master clock rate of the USRP embedded feeds both the FPGA DSP and the codec chip. Hundreds of rates between 32MHz and 64MHz are available. A few notable rates are:

- 64MHz - maximum rate of the codec chip
- 61.44MHz - good for UMTS/WCDMA applications
- 52Mhz - good for GSM applications

## Set 61.44MHz - uses external VCXO

To use the 61.44MHz clock rate, the USRP embedded will require one jumper to be moved, and X4 must be populated with a 61.44 MHz oscillator.

- J15 is a three pin header, move the jumper to (pin1, pin2)
- 357LB3I061M4400 is the recommended oscillator for X4

Note: See instructions below to communicate the desired clock rate into the UHD.

## Set other rates - uses internal VCO

To use other clock rates, the jumper will need to be in the default position.

- J15 is a three pin header, move the jumper to (pin2, pin3)

To communicate the desired clock rate into the UHD, specify the a special device address argument, where the key is "master_clock_rate" and the value is a rate in Hz. Example:

    uhd_usrp_probe --args="master_clock_rate=52e6"

# Hardware setup notes

## Front panel LEDs

The LEDs on the front panel can be useful in debugging hardware and software issues. The LEDs reveal the following about the state of the device:

- LED A: transmitting
- LED B: fpga loaded
- LED C: receiving
- LED D: fpga loaded
- LED E: reference lock
- LED F: board power

# Miscellaneous

## Available Sensors

The following sensors are available; they can be queried through the API.

- ref_locked - clock reference locked (internal/external)