@ESP_Sprite - thanks again for looking at it.

One quick question - is there a reference which explains I2S_COMM_FORMAT_PCM | I2S_COMM_FORMAT_PCM_LONG (vs I2S_COMM_FORMAT_I2S | I2S_COMM_FORMAT_I2S_MSB)?

WRT Grounding: Oh boy, I should have thought of that :oops:

I'd been trying to figure out why ...

Thanks ESP_Sprite!

>> I'd like to see what your setup looks like.
Not totally sure what you'd like, but I attached a picture of the setup.

>> You're shuffling bits and forth at 3MHz; at rates like this the cabling gets somewhat important.
I just ran a test at a much slower 8kHs x 16 x 2 = 256KHz ...

Pointing out a couple things you may already know:


The ESPs I2S apparently has a noise issue https://esp32.com/viewtopic.php?f=17&t=1026&p=4589&hilit=webradio+noise#p4523
The ESP32 has a built in DAC - though it's only 8-bit/low quality https://www.esp32.com/viewtopic.php?t=1339

One simple ...

Question for the Espressif team:

If you set .bits_per_sample to 24-bits, how is the data aligned in the returned buffer? is it padded out to 32-bits?

For these tests the master and slave where swapped - so the sender is the master (I2S_MODE_MASTER) and the receiver is the slave. Everything else is the same as with the prior tests:


Run__________# Correct___# Wrong
1st @48000______ 1009________11
2nd @44100______876________128
3rd @8000 ...

Good suggestion.

I don't know of a way to directly control clock speed in I2S. My understanding is that the SCK/BCLK is the sum of: sampling rate * bits of precision * # of channels, e.g:

44.1 kHz × 32 × 2 = 2.8224 MHz
So, set up some tests using 32-bits, 2-channels. The "Sender" transmitted ...

Testing two ESP32's connected via I2S:


Sender - Fills a buffer with 32-bit values. Then calls i2s_write_bytes to send the buffer over and over.
Receiver - calls i2s_read_bytes to receive the data into buffers. Then prints the values it received.
For the initial test, the sender's buffer was ...

Possibly, but it seems more bit-level - like bits are shifted and possibly repeated.

Thanks BuddyCasino!

At first blush that looks like what I'm seeing - just the channels reversed. So, either a) there's some sort of bug/problem in HW or b) there's a problem in the code and/or my understanding. I suspect it's a)...

Unfortunately, I think the bigger problem is this forum ...

Out of curiosity, what are you using in instead?