Hi !
I’m designing a synth and I need some help for reviewing my schematic before starting the layout.
The things I’m not really sure about are :
Is the CODEC compatible ?
I’m not using any inputs (neither MIC nor LINEIN), only line out and headphone out, but the “AudioOutputI2S” object does not shows the WM8731 as a compatible CODEC chip, but it does with the “AudioInputI2S”. I think there is no problem but... I ask anyway.
Are my I2S connections OK ?
Pin 1 (MCLK) CODEC > PIN 23 (MLCLK1) Teensy
Pin 7 (BCLK) CODEC > PIN 21 (BCLK1) Teensy
PIN 9 (DACLRC) & 11 (ADCLRC) CODEC > PIN 20 (LRCLK1) Teensy
PIN 8 (DACDAT) CODEC > PIN 7 (RX2) Teensy
Pin 10 (ADCDAT) CODEC >PIN 8 (TX2) Teensy
I’m not using any audio inputs, so do I need to connect ADCLRC and ADCDAT ?
Do I have to connect the analog inputs I’m not using to ground as I did ?
About the 33R resistors
I based my design on the “TGA Pro” from Blackaddr who is using 33R resistors on several lines, but I don’t really know why he did this. I know this codec is really sensitive to ringing so I thought it is to prevent this but I don’t really know. MIKROE did the same with 27R resistors, but the datasheet does not mention this at all.
Last question, this one related to the layout
For the first time I want to layout a 4 layers board, with ground plane and power plans as inner layers. But I don’t understand one thing : a rule is to place decoupling capacitors close from IC’s power pin, but if there is no trace between them but a power plan (with the cap connected to the plan through a via), will the current goes straight from the cap to the IC's power pin ? When I try to figure it out I don’t understand, physically, why the current will go straight from pin to pin and why it will not find another path through the power plane as soon as there is no concrete trace connecting the two pins. I know that current always find the shortest path but I don’t know… it is like all the power signals will be mixed in a kind of “clusterfuck”. Same question goes with other power lines, not only decoupling caps and IC’s power pin.
I’m designing a synth and I need some help for reviewing my schematic before starting the layout.
The things I’m not really sure about are :
Is the CODEC compatible ?
I’m not using any inputs (neither MIC nor LINEIN), only line out and headphone out, but the “AudioOutputI2S” object does not shows the WM8731 as a compatible CODEC chip, but it does with the “AudioInputI2S”. I think there is no problem but... I ask anyway.
Are my I2S connections OK ?
Pin 1 (MCLK) CODEC > PIN 23 (MLCLK1) Teensy
Pin 7 (BCLK) CODEC > PIN 21 (BCLK1) Teensy
PIN 9 (DACLRC) & 11 (ADCLRC) CODEC > PIN 20 (LRCLK1) Teensy
PIN 8 (DACDAT) CODEC > PIN 7 (RX2) Teensy
Pin 10 (ADCDAT) CODEC >PIN 8 (TX2) Teensy
I’m not using any audio inputs, so do I need to connect ADCLRC and ADCDAT ?
Do I have to connect the analog inputs I’m not using to ground as I did ?
About the 33R resistors
I based my design on the “TGA Pro” from Blackaddr who is using 33R resistors on several lines, but I don’t really know why he did this. I know this codec is really sensitive to ringing so I thought it is to prevent this but I don’t really know. MIKROE did the same with 27R resistors, but the datasheet does not mention this at all.
Last question, this one related to the layout
For the first time I want to layout a 4 layers board, with ground plane and power plans as inner layers. But I don’t understand one thing : a rule is to place decoupling capacitors close from IC’s power pin, but if there is no trace between them but a power plan (with the cap connected to the plan through a via), will the current goes straight from the cap to the IC's power pin ? When I try to figure it out I don’t understand, physically, why the current will go straight from pin to pin and why it will not find another path through the power plane as soon as there is no concrete trace connecting the two pins. I know that current always find the shortest path but I don’t know… it is like all the power signals will be mixed in a kind of “clusterfuck”. Same question goes with other power lines, not only decoupling caps and IC’s power pin.