XMEGA Xprotolab Breakout Board

Introduction

The XMEGA Xprotolab is a convenient mixed-signal oscilloscope (MSO) with an arbitrary waveform generator fitted to a DIP form factor. However, it is sometimes necessary to use this oscilloscope with other instruments that use BNC connections (i.e. sensors, frequency counters, etc.) or with oscilloscope probes.

Therefore, this breakout board converts the two analog inputs, arbitrary waveform generator, and trigger pins to BNC jacks. In addition, this board also adds a 5V switching regulator so that the Xprotolab can be supplied by a 6.3-30V power supply, as well as a Bluetooth module that allows the wireless use of the Gabotronics Xscope computer interface. Two rows of I/O pin headers are used to bring the Xprotolab I/O pins to the edge of the board.

Creation

To make this board, I first created the schematic and board layout, then sent this to OSH Park for production. The BNC jacks are from Sparkfun; therefore, the parts used in Eagle are from the Sparkfun library (linked in the GitHub repository below). To connect these, I used 0.024 inch traces on the top layer, with vias connecting the top and bottom ground planes surrounding them in an attempt to shield the traces.

To connect the Bluetooth module, I had to use air wires to connect to the expansion jack on the right of the Xprotolab, since these pins are not broken out anywhere else. The 3V3 for the module is derived from the 3V3 output on the Xprotolab; therefore, it will work whether powered by the DC barrel jack or the USB connector on the Xprotolab. The top LED (LED2) is the 'Connect' LED for the Bluetooth module, and is typically green. The bottom LED (LED1) is the 'Status' LED and is typically red. On my board, I switched these two around, so when the COM port is connected, the red LED turns on.

PCB

After sending this file to OSH Park, I received the PCB a few weeks later in the mail.

Stencil

In addition, I also had a stencil made by OSH Stencil to do solder pasting and reflow for the SMD parts.

After reflowing the parts, I finished soldering the remaining components. For the switching regulator, I used a DE-SW050 5V switching regulator from Dimension Engineering, which uses the same pinout as a LM7805 regulator. Therefore, any 5V regulator that fits this footprint can be used.

Attaching Air-Wires

To attach the air-wires for the Bluetooth module, I cut four female-female jumper wires and soldered them to the PCB through the plated through-holes. In revision 1a of the board, you can solder male pin headers to the PTH pins and use short female-female jumper wires without modification. In any case, only the first four pins (from the left) are used.

For the female pin headers holding in the Xprotolab, the top row requires 12 pin headers, so 12 were cut out. The bottom requires four sets of two pin headers, so these were cut to size and soldered in.

In general, I find that soldering the lowest components first tends to be easier, so I soldered the female headers first, then the 90-degree male headers, the DC barrel jack, the four BNC jacks, and lastly the switching power regulator.

Using the Computer Interface

To use the Bluetooth module with Windows 10, go to Settings > Devices > Bluetooth. Turn Bluetooth on if needed. Then, if the Xprotolab Breakout Board is turned on, you should see the RNBT-A256 device appear. Click on the device, click on pair, and accept the Bluetooth passcode.

If needed, check the COM port in Device Manager.

In most cases, the correct COM port will be the first one. In the case above, I had overlapping COM ports, so I just changed the port to a free one under the advanced properties.

Then, open Gabotronic's Xscope and go to the 'Options' tab. Select the COM port noted from before, and click on connect. The software should connect to the Xprotolab over the Bluetooth link and reflect the Xprotolab's screen.

Resources

For additional information on the Xprotolab or the Xscope software, follow this link to Gabotronics' website.

I hope you enjoyed this write-up. Feel free to leave comments or suggestions below. The attached Eagle files are free to use, modify, or distribute.

Note

*The difference between Rev. 1 and 1a PCBs is that 1a has mounting drill holes in the PCB, and has larger drill holes for the Bluetooth module air-wires. The DC input silkscreen is corrected from "1.3 - 30V" to "6.3 - 30V".