Etherkit – AB4UG Radioblog

Another Si5351A board

A few days ago, Jason/NT7S announced the Etherkit Si5351A breakout board was getting an upgraded TCXO oscillator with improved performance. I’ve already got a few of them waiting for me to put to work, so why not add another one.

Yay, @etherkit Si5351A breakout board with new TCXO arrived. pic.twitter.com/FdtoKTOYSg

— imabug (@imabug) April 19, 2016

Unlike the previous boards I bought (from the crowdfunding campaign), the latest versions now come fully assembled except for the header pins. If the thought of soldering tiny surface mount devices was keeping you from trying the breakout board, worry no more.

The 10 mW WSPR beacon app note looks pretty interesting, and I think it would be fun to try to get one set up once we’re in the new house. I’d love to see how far it could be heard.

We’ll hopefully be in the new house in a few more weeks. I’m looking forward to getting the shack and workshop set up again so I can get to playing.

Si5351 on the oscilloscope

The Si5351 breakout boards all work, at least according to the frequency counter, so I thought I’d put the oscilloscope on one to see what was coming out. I just connected the output of the Si5351 board straight to the oscilloscope using an SMA/BNC pigtail. I’m sure it’s a totally incorrect way of doing it, but all I wanted to see was if I got a waveform and if it changed when I changed the Si5351 frequency.

I’ve been told that the Si5351 output is a square wave, and at kHz frequencies, that’s what I get. This is the 10 kHz waveform. Nice looking square waves.

Etherkit Si5351 10 kHz waveform on the oscilloscope

Going up a few orders of magnitude to 1MHz, the shape of the waveform loses its squareness, most likely due to the way I’ve connected things (impedance mismatch, improper loading and all that). But, as the time base shows, it’s a much higher frequency signal.

At 10 MHz, there’s even more distortion of the waveform, but definitely higher frequency.

Up at 20MHz, things are looking pretty triangular.

So, TIL:

My Si5351 board really works! Yay!
You can’t just connect things willy-nilly to an oscilloscope and expect good results. (I already knew this, just wasn’t important for this purpose.)
There are still some things I need to learn about using this particular oscilloscope.

Working Si5351 breakout boards

Finished assembling a non-TCXO version of the Etherkit Si5351 breakout board today. With three boards worth of experience behind my back now, this one went pretty smoothly. Set this one up to use in a breadboard like board #3.

Then it was off to test them out. I used Jason’s Si5351 Arduino library (as of this writing, the ‘jason’ branch is the most current one) and one of the example sketches with one of my *duino boards, connected the M³ frequency counter and wired everything up.

Much to my surprise, the first board (with the TCXO) worked, and the frequency was pretty much bang on, at least to the resolution the M³ meter is capable of.

The non-TCXO board I assembled today was off by a bit (~900 Hz), but Jason says that’s normal for the regular oscillator.

The other two TCXO boards worked as well and were right on frequency.

Now I need to work on more precise frequency measurements so I can work out the calibration offset for each of the boards.

Etherkit Si5351A breakout board three ways

Finished assembling the last of the Etherkit Si5351A breakout boards I received from Jason‘s Indiegogo campaign. Since I had three of them to play with, I decided to do a few different configurations.

Board #1 is a pretty conventional setup with the header pins pointing up. Lays flat on a surface and could be mounted inside an enclosure if needed.

Etherkit Si5351 board with conventional pin layout

Board #2 I used female header pins to make interfacing with my *duino boards easier, since almost all the jumper wires I have are male/male.

Etherkit Si5351 board using female connector pins

Board #3 I set up to make it easy to use with breadboards. The header pins are pointed “down” so that I can stick the breakout board into a regular breadboard. I also added female headers to the output in addition to the SMA connectors.

Etherkit Si5351 board with pins down for breadboard use

I still need to test the boards out to make sure they actually work. I think if I’m going to have any problems with the boards, it will probably be with the soldering of the Si5351A chip.

Building the Etherkit Si5351 breakout board

Spent some time at the workbench putting together the Etherkit Si5351 board that arrived the other day.

Although it’s pretty much all surface mount, everything is on one side of the board, and the part count is relatively low so assembly is pretty easy. The fine pitch of the Si5351 chip makes soldering it more challenging, but generous use of solder flux helped the solder flow where it was supposed to go.

After the Si5351 came the TCXO crystal. The large pads make this part relatively easy to solder.

The transistors and 3.3V voltage regulator were the next components to get soldered on. These were pretty easy to do. As with the Si5351, a good amount of solder flux helps with the voltage regulator.

The remaining passive components (4 capacitors and 4 resistors) finish up the surface mount components. These are pretty easy to solder on. Tack down one side with a bit of solder, then solder the other side.

With all the surface mount components on the board, that leaves just the header pins and the edge mount SMA connectors. Easy peasy.

And with that, the Etherkit Si5351 breakout board is finished! Next step is to connect it up to one of my *duinos and see if it works.

I have two more boards to assemble, and some of the things I learned assembling this one should make the other two a little smoother.