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Just noise with Teensy 3.6 and Audio Adaptor Board
Dear forum members,
I have attached the audio adaptor board to the teensy 3.6. The "SdCardTest" sketch and the "Part_1_03_Playing_Music" sketch both works (based on the output of the serial monitor), but I just hear noise. I have recorded the output of the headphone with my mobile: https://dl.dropboxusercontent.com/u/...audioboard.m4a
Does anybody has an idea what's wrong?
Exactly how did you do this? A photo would be good.
I have attached the audio adaptor board to the teensy 3.6
Here it is:
You might want to check every single connection.
Originally Posted by Frickelpiet
Would have been much easier to stack the boards..
I have checked and double checked every single connection.
+ 3,3 V is connected to a pololu regulator (3,3 V)
GND is connected with GND of the regulator and the teensy
All other connections are as follows:
LRCLK pin 23
TX pin 22
SCL pin 19
SDA pin 18
VOL pin 15
SCLK pin 14
RX pin 13
MISO pin 12
MCLK pin 11
SDCS pin 10
BCLK pin 9
MOSI pin 7
MEMCS pin 6
I have figured out that the wires are the problem. I think they are too long. Sometimes the board plays the test files until I touch the wires.
Or perhaps one or more of those wires has a bad solder joint?
What about pull up resistors for the I2C bus to stabilize the signals?
I had a similar problem with a T3.2 and an audio adaptor connected by wires that were about 3 inches long. It seems that there can be some clock skew and cross coupling in those wires, especially without a good low inductance ground between the two boards. This causes the clock and data to get out of sync, resulting in noise. Adding some copper foil under the wires and separating each one cured the random rude sounds. Kapton tape holds the wires to the copper foil, which is grounded in multiple places. Other sound anomalies were cured by replacing the cheap SD card with a true Class 10 card. The project has worked perfectly ever since. Pictures are before and after the added ground.
I have added the pullup resistors as recommended, and with them the audio board works better. But sometimes I still get the noise. I think I will solder the audio board on the top of the teensy.
Maybe small series resistors on the MCLK and BCLK outputs could also help?
Same sort of trouble we've seen many times with OctoWS2811... before PJRC started selling the board with 100 ohm resistors and connectors for using CAT5 or CAT6 cable. The fast edges of the clocks and long wires can cause a lot of crosstalk.
Fighting with the same Issues at the moment.
Seems to be the I2S Signal.
No problems with a T3.1 with the same setup.
I'll try the hint with the resistors when i'm back in office.
Please post photos of how you've actually connected the wires. Show (don't tell) how you've really connected everything.
So this is the actual Setup:
Problem seems to be Pin 11 - MCLK.
Adding a 1K Resistor improved the stability a lot. (chaos when touching the resistor pins - same as before)
Im sorry I could not find the 10K Resistors. It stopped working with a 130K Resistor.
then I bridged Pin 11 from Teensy and Audio Board with a piece of a Guinness can....
(ok... in fact, i used one of the wires of a resistor.... i'm still not in office, so i have to improvise)
problems were gone then.
Since I have soldered the Audio Adaptor Board on top of the teensy everything works flawless.
Last edited by Frickelpiet; 02-02-2017 at 04:28 PM.