Alternative Installation Options

In addition to Plug-n-Play installation on the National Instruments RoboRIO™, navX-MXP’s flexible design accommodates several additional installation options.

One-wire Connect via “Floppy-disk” extension cable

If mounting the navX-MXP circuit board directly into the RoboRIO’s onboard MXP connector is not possible, a “Floppy-disk” extension cable can be used to place the navX-MXP circuit board up to a few feet away from the RoboRIO. This installation method supports the I/O expansion capabilities, since all MXP connector signals are carried over the extension cable.

Note that higher-speed signals such as those found on the SPI and I2C bus, and noise-sensitive analog signals like those on the Analog Input and Output pins may be negatively impacted by longer distances and electro-magnetic interference, so high quality shielded cabling and shorter distances may be called for.

These extension cables are available online at AndyMark:

One-wire Connect via USB cable

By using a USB Mini-B type (Male) to USB A type (Male) connector, navX-MXP can receive both power and also communicate with the RoboRIO.

This installation method allows the navX-MXP circuit board to be placed longer distances away from the RoboRIO than via the “Floppy-disk” extension cable method. However, this installation method does support the I/O expansion capabilities, since the MXP connector signals are not routed over the USB cable.

usb_minib_cable

Low-level Connect via Power and Signal pins on MXP Connector

If any of the “one-wire” methods described above is not desirable, you may also interface to the navX-MXP circuit board using the Power, Ground and I2C/SPI/TTL UART signals on the MXP Connector.

I2C

To use the I2C interface without directly plugging the navX-MXP circuit board into the RoboRIO MXP connector, first ensure that the navX-MXP circuit board has power (either via the USB connector, or via the +5VDC pin on the MXP connector).

Next, make sure that the digital ground from the host computer (e.g., the RoboRIO) is connected to one of the GND pins on the MXP connector.

Finally, connect the SDA and SCL pins on the host computer (e.g., the RoboRIO) to the corresponding SDA and SCL pins on the navX-MXP circuit board.

Note that the I2C bus expects that the SDA and SCL pins be pulled up with a pull-up resistor on each line. The RoboRIO internally pulls these lines high.

The I2C pins are 5V tolerant, so the host computer can use either 5V or 3.3V DC levels on these pins.

SPI

To use the SPI interface without directly plugging the navX-MXP circuit board into the RoboRIO MXP connector, first ensure that the navX-MXP circuit board has power (either via the USB connector, or via the +5VDC pin on the MXP connector).

Next, make sure that the digital ground from the host computer (e.g., the RoboRIO) is connected to one of the GND pins on the MXP connector.

Finally, connect the CS, CLK, MISO and MOSI pins on the host computer (e.g., the RoboRIO) to the corresponding CS, CLK, MISO and MOSI pins on the navX-MXP circuit board.

The SPI pins are 5V tolerant, so the host computer can use either 5V or 3.3V DC levels on these pins.