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Always refreshing how Paul shares design and design process info.

I've used a one byte per second serial over USB connection from a PC to discipline a teensy audio clock to the PC system clock. Works well.

Note that a GPS requires far less noise during acquisition. So in some cases, you can power up the GPS, acquire a lock and then power up the noisy circuitry.

Distance (even say from 1" to 3")...

The easiest way to reduce noise is to go with the trend - do everything possible in the digital domain.

Yes, marketing is critical - which is why inferior technical specs don't mean non-competitive.

Always be interested in the competition. Even if you think "that's not very competitive because ..."

Disabling interrupts around the call made it much worse. My working assumption - changing speeds simply takes too long to be useful in my use case.

I find it disappointing that while there was a pre-existing usable and popular API (Arduino), the RasPi foundation went off and created yet another API. But as I mentioned above, they didn't need...

Looks like it doesn't disable interrupts while waiting - seems like a potential source of problems.

I could check with the scope, but does anyone know how long set_arm_clock() takes to execute? I see that it includes wait loops. Also that it's changing voltage - which might have some side...

I'm using SPDIF3. It's a confusing issue because I've seen all of crashes, distorts and works fine. Distortion is the most common. I am doing a lot of processing - a simple pass-through may not...

Strange, that is basically the code I tested with. I just tried a different placement of the speed changes and the program locks up (switching between 816 Mhz while processing and 528 Mhz when idle...

I would guess that there would be a lot of value in teensy wrapper libraries that are compatible with the pico libraries. Ie, an easy migration path for users who start on the low cost pico and want...

A clue: my DAC sees an interruption in toslink output. Perhaps the audio PLLs get reset?

Unfortunately, it creates audio glitches if one switches back and forth.

Look at the upgrade_firmware() routine and add code to open the file and read characters from it instead of the serial port. Others can say more about how to use the SD card.

What was the conclusion on this? Is there an easy way to jump to 912 Mhz for a brief period?

You can easily write code to load a teensy .hex firmware file from an SD card (or modbus) if you use the Flasher4 library.

A claimed reason for the pico is that linux (used on their other models) isn't good at real-time I/O. But all they had to do to fix that was change the OS to leave one core completely untouched by...

Following the manufacturer recommendation sounds reasonable. Is there something that prevents the battery from being discharged to an unsafe voltage?

A differential ADC on the Teensy 3.6 (Pins A10 and A11) should work well for this application.

Don't worry about the ":02 0000 02" lines, they aren't code values. But for now, do manually combine any ":04 XXXX 00" lines.

No doubt there are some users who are able to "insert the SD card I mailed you" and not "install this software on your PC and then ....". You can start with "Flasher4" if you want to develop...

If you just want an easy low noise teensy output solution, run toslink to an off-the-shelf DAC/amp.

i2sflew: I highly recommend that you get used to typing your circuits into LTSpice. You can even add noise to the power supply or input. Not perfect, but you will learn a lot.

How does it sound when you run from batteries?

"the AD8656 can drive capacitive loads up to 500 pF ..."

So if you are planning to us it there, think twice about that 33uF.

> a DSB is mandatory at the end of interrupt-code

I believe it should also be used when disabling interrupts from non-interrupt code.

> SCB_AIRCR = 0x05FA0004;

Of course such things...

You might be better off just ordering this:

https://www.pjrc.com/store/audio_ground_isolator.html

It would be really nice if the flasher code could directly accept any .hex lines it is likely to receive.

I would study the example below. Look closely at how/where "client" is set.

https://gist.github.com/atomsfat/1813823

> A simple hardware diagnostic using patterns of red LED blinks is also planned

Nice! - black boxes are hard to debug. Would be very helpful to distinguish between "loader can't talk to MCU",...

That is my concern. Some protocols are likely to lose exactly an entire line. This could get flashed and the error might not be immediately obvious.

> you need to type in ":flash XXXX", where XXXX is the number of lines reported by the program

I recommend that you don't do this. Type in ":flash XXXX", where XXXX is the number of lines you...

For speaker analysis and correction, this is great.

https://www.roomeqwizard.com/

If you want to do convolution based correction, then just use the impulse response from REW and also use...

Yes, specifically "fast, partitioned convolution".

While it's only necessary for high resolution at low frequencies, I am able to run 12288 taps, stereo.

OK, I checked and some notes:

T4 with a small heat sink attached
It runs about 45C (far far different than the graph)
Slowing from 600 to 528 is only a couple of degrees cooler
wfi makes no...

In many cases, one could include this in their idle loop, which I understand reduces power/heat more than slowing down to 450 mhz.

asm volatile("wfi");

My guess is that at 450 mhz, it will last a very long time. And most applications won't notice the slower speed.

There was some discussion of strlcpy(). IMO, don't just use it, use it and check the return value. Ie:



if (strlcpy(dest, src, sizeof(dest)) > sizeof(dest))
handle_error();

3 years life at 600 mhz - that could be a problem.

Sure, you could pack four 10 bit samples into every five bytes. But consider other approaches - like a teensy 4.1 or a larger sd card.

My experience is that paste is better, even when you don't have a stencil. But I save time and frustration - unless JLCPCB puts most of the parts on, I always order a stencil. More advice - use a...

I agree with tomas. Is there a tool for predicting how many bits you need for how much distortion?

Consider either headphones (low bass with low power) or a subwoofer (which will need size and power).

For about $15, you can buy an external TOSLINK DAC box. Not the lowest cost option, but will probably outperform the PT8211.

Yes, it works on both 4.0 and 4.1.

See here for a newer, better teensy 3.x version:

https://forum.pjrc.com/threads/43165-Over-the-Air-firmware-updates-changes-for-flashing-Teensy-3-5-amp-3-6

Nice work Joe.