Adafruit I2S Stereo Decoder - UDA1334A (only working when WSEL or BCLK connected to oscilloscope probe!)

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1

Hi Guys,

I have this wired up to a Teensy 4 (3.3v), when powered on the only thing that was coming out of it was low level white noise. The test application is trying to output a sine wave.

So I got the oscilloscope and started probing to check I had it connected properly and the moment I probed WSEL it jumped into life and started working, probing BCLK has the same effect.

When no data is being sent to it probing these pins also removes the low level white noise.

Has anyone got any ideas of what might be going on here?

Many thanks

Andy

2

I do believe the oscilloscope probes will introduce “some” capacitance. microfarads or picofarads, its only a small amount. Not sure if that helps but its all I have at the moment.

3

Thanks for the reply, any idea why this would kick the UDA1334A into life?

4

No, its just something I remembered from when I was still working as a tech.

How do you have the two connected? Headers jumpers wise?

5

It is all on a breadboard, also with a ILI9341 LCD module.

I will unwire it all today and redo it…

6

Ok, I re wired it without the LCD on a different breadboard. Same issue.

To get it to work a trailing wire on WSEL works, in the picture the orange one.

I will order another one and see if that acts the same way.

IMG_2727
IMG_2727.JPG480Ă—640 155 KB

7

Its a bit hard to follow the wires, all the same color etc. I do notice a jumper linking one of the V3 to V4 rails, but not on the other?

8

Thanks for all the interest.

The bottom one is the ground, if you look at the black and red lines the red line is broken which is why I have the jumper there.

Now I have wired up the touchscreen I am getting very strange behaviour, touching the screen makes the DAC work!

I have another teensy 4 here I will try latter to see if it is the same, if that doesn’t fix it I will order another DAC and see if that works…

9

Ah, OK, usually both rows would have a break in the middle, I missed that the black line didn’t have a break in it.

10

Some of the soldering looks a little iffy to me. Right hand side of the DAC as it is in the picture. Vin, 3V0, GND etc. Have a look see anyway. Maybe resolder them.

11

A “little iffy” might be being a little bit kind, some might say hopeless!

I need to solder the headers on the other teensy so I will give the DAC a bit more attention with the soldering iron :)

12

Ok, desoldered the DAC and had a check under the microscope, same problem.

Soldered headers onto new Teensy 4 and tried that, same problem.

So I will order another DAC and try that. I will let you know the outcome and once again thanks very much for your interest in this.

Cheers

Andy

13

No problem, I enjoy coming here, gets the brain working.
Plus I usually learn something in the process of helping out.
I have a couple of Arduino’s, and a couple of MicroBits. I don’t play with near as much as I should.
I spend most of my time tinkering with my raspberry Pi’s.

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14

@alphanumeric

Hi Kerry,

The new one arrived and works perfectly, so the original one must be faulty I guess.

I haven’t tried it with the touchscreen yet but I’m guessing that will also be fine now, I will let you know when I get round to attaching it up.

Cheers

Andy

15

I’ve played around with a 16x2 LCD on my Arduino but thats about it. It’s now siting there waiting for me to find a use for it. It came in a kit I got here at Pimoroni.
https://shop.pimoroni.com/products/arduino-mkr-iot-bundle
With the cold winter nights approaching I’ll likely get into some of it and maybe learn something.