Hey all,
I'm working on a guitar pedal that uses a Teensy 3.2 with an OLED wired via I2C that also has a separate Reverb guitar effect in the same enclosure.
I'm running into a high pitched noise issue (sounds like those old dot matrix printers!), but this noise is only audible when the I2C pins are transmitting data to the OLED. So when the Teensy is transmitting the print data (u8g2lib library) to the OLED, I can hear a high pitched sound. As soon as it's sent, the noise stops.
At first I thought it was the OLED generating the noise, but it can display whatever text, and there is no noise. The noise is only there when transmitting data.
Here's everything I've tried:
-10uf + 100nf MLCC decoupling on the two 9v (I also have a 330nf decoupling cap here) to 5v regulators for the Teensy & the OLED. Same decoupling combination right at the Teensy's VIN/GND and right at the OLED's VIN/GND.
-Shielded wire for the OLED's SDA (data) wire. Length is about an inch long to the Teensy, too.
-Audio circuitry is on one side of the enclosure. Digital circuitry is on the opposite side.
-I tried my best to star ground and keep the audio grounds as separate as possible from the digital grounds.
-Lowering the I2C Bus clock speed which greatly affects the pitch/tone of the noise, but is still noticeable
At this point, I don't think it's an issue with sensitive circuits and their proximity to the SDA/SCL wire. It seems like it's just noise that's being injected right into the ground or audio path, if that makes sense?
I'd appreciate any or all comments, thank you!
I'm working on a guitar pedal that uses a Teensy 3.2 with an OLED wired via I2C that also has a separate Reverb guitar effect in the same enclosure.
I'm running into a high pitched noise issue (sounds like those old dot matrix printers!), but this noise is only audible when the I2C pins are transmitting data to the OLED. So when the Teensy is transmitting the print data (u8g2lib library) to the OLED, I can hear a high pitched sound. As soon as it's sent, the noise stops.
At first I thought it was the OLED generating the noise, but it can display whatever text, and there is no noise. The noise is only there when transmitting data.
Here's everything I've tried:
-10uf + 100nf MLCC decoupling on the two 9v (I also have a 330nf decoupling cap here) to 5v regulators for the Teensy & the OLED. Same decoupling combination right at the Teensy's VIN/GND and right at the OLED's VIN/GND.
-Shielded wire for the OLED's SDA (data) wire. Length is about an inch long to the Teensy, too.
-Audio circuitry is on one side of the enclosure. Digital circuitry is on the opposite side.
-I tried my best to star ground and keep the audio grounds as separate as possible from the digital grounds.
-Lowering the I2C Bus clock speed which greatly affects the pitch/tone of the noise, but is still noticeable
At this point, I don't think it's an issue with sensitive circuits and their proximity to the SDA/SCL wire. It seems like it's just noise that's being injected right into the ground or audio path, if that makes sense?
I'd appreciate any or all comments, thank you!