TeensyMaestro

K3CDY · August 17

Len, Simon - I'm interested in piping the TeensyMaestro's internal CW sidetone audio to a rear-panel connection so I can plug it into my desktop audio interface. I'm hoping the internal TeensyMaestro sidetone signal chain may offer reduced latency, compared to my existing setup which has several software hops before it hits my headphones.

Currently my signal chain is: CW Key → Halikey USB Interface → USB hub → Mac → SmartSDR → USB Audio Interface → Headphones.

My proposed signal chain would be: CW Key → Teensy Maestro Key input → TeensyMaestro Audio Out → Audio Interface (zero latency) → Headphones.

Electrically, what kind of signal is sent to the internal speaker (line level)? Is there a way to control the sidetone audio level in the TeensyMaestro software? What's the current CW sidetone latency in the TeensyMaestro (i.e., time from keyer paddle press to internal speaker audio generation)?

I'm thinking I would wire up a switching audio jack that disconnects the internal speaker when a plug is inserted. My audio interface can handle anything from line level to mic level.

KD0RC · August 17

Hi Bill, wow… Yes, I can see some latency there! The TeensyMaestro sidetone is just a GPIO pin toggled at the desired frequency. So negative peaks are at 0 V and positive peaks are at 3.3 V. I don't know how that aligns with the audio world in terms of line level to your audio interface. I would start with a 10K p.ot across the sidetone output with the wiper to your interface through a 1 or 10 uf coupling capacitor. I think that will allow you to set the volume reasonably well. I am not sure if you need a headphone amp or not. We can chat more about that over lunch on Wednesday.

While I haven't measured the latency from key close to sidetone output, I would guess that it is under 1 millisecond. Way less than perceptible by the human ear.

I really need to put a controllable amp on the output along with a low pass filter to make the tone more pleasant.

I found a chart that might suggest that we are in the ballpark:

Using the 10K variable resistor (can't say p.o.t here…), you should be able to get a good audio level out.

K3CDY · August 17

Thanks Len!

I'm guessing since you're simply toggling a GPIO digital output, you're essentially generating a square wave (which can sound pretty unpleasant). Adding a true audio output module to the TM would make this a CW monster.

Perhaps something to look forward to in your next revision!

G7UFO · August 21

Know there are a few US based OPs looking to provide boards over on the groups.io but thought I'd cross post this in here as well.

I've been chatting with Simon and Len about making a kit available via my shop.

This is very much in the exploratory stage and I've started putting together sources over this side of "the pond" for the components as well as ordering an (initially) small batch of PCBs. My aim is to provide a kit version of this for people to assemble themselves. I'd also design and make include a 3D printed case (which will also be freely available for download).

In order to gauge how much interest there would be I've added a form here. I won't hold you to a purchase (especially since I can't provide a price yet!) but if there is enough interest I'll start ordering components.

Many thanks to Simon and Len for all their work.

KD0RC · August 21

Hi Neil, I notice on your form that you don't mention the front panel, but I think that you intend to include the PC board as well as the front panel, correct?

You might want to reach out to Bill, K9HZ. He won't be providing kits, but will have boards for sale at a very reasonable price.

G7UFO · August 21

Hi Len,

In short - yes! I'll update that page to be clearer. The small batch of PCBs I've ordered include the front panel.

Slightly longer answer; if I can figure out a nice way to include the front panel into my custom case then it'll likely help reduce the cost a little. My only concerns are that it'll add complexity to the print (nozzle size mainly) and frankly that the 3D printed version may just not look good.

I'll reach out to Bill - thanks for the tip!

NV0E · August 21

Hi Everyone,

We just discovered there was an error in the BOM in the Github. The BOM contained a Digikey URL to a 'Teensy 4.1 without ethernet'. It turns out this doesn't mean without ethernet RJ45 and cable, but instead without ethernet chip on the Teensy board. The BOM has been corrected and I've listed several sources for the correct Teensy. Apologies for the incorrect link.

73,

Simon, NV0E.

G7UFO · August 25

The picture below was out of date pretty fast as another load of parcels arrived. I'm expecting PCBs (inc front panels) to arrive tomorrow along with a bunch more components this week.

I'm updating this page as I go - it also has a form at the bottom to receive updates via email.

KD0RC · August 28

TeensyMaestro V2.001 is now available on GitHub:

https://github.com/KD0RC/Teensy-Maestro-for-Flex-6000-radios/releases/tag/V2.001

*****************************V 2.001 * ***************************
Fixed bug where HW V2 display is not turned off when power button is used to shut it off.  
Fixed bug where second slice cannot be started from TeensyMaestro if RX ant is not ANT1.  
Simon, NV0E fixed Flex Discovery to properly use the VITA header instead of arbitrary payload data  
   to identify a Flex discovery UDP packet.  
Added startup beep so you know that you actually hit the power button (HW V2 screen is a bit slow to start).

I wanted to get this set of minor bug fixes out before tackling the next update request (2BSIQ contesting suggested by Ron, WV4P and Levi, K6JO).

Note that there are now two zip files containing the .hex file to be loaded into the Teensy board.

If you are using the new PC board with the ST7796S display, use the file ending in HW2. If you built the original point-to-point wired version with the HX8357 display, use the file ending in HW1.

TeensyMaestro

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