HI,
I'm writing on behalf of my customer testing the EVM. According to them, they always got an incorrect detection between 3 & 4poles audio jack. However if the insertion speed increases the accuracy improves. May I know if there is any settings or tuning can be done to improve the detection robustness?
Currently, all settings are as default.
Thanks,
Christina
Hi Christina,
There are two likely problems that could be causing this issue:
1. False triggering of the /DET_TRIGGER pin. How the EVM audio jack is set up is that when no accessory is inserted pin 5 and pin 2 of the audio jack are shorted together. When the tip of the audio connector is inserted pin 2 and pin 5 connection is broken and the /DET_TRIGGER pin goes low. Audio detection begins after the debounce period (90ms by default). If the connector that is inserted breaks the connection between pins 2 and 5 before it is fully inserted a false impedance reading can occur. One solution is to increase the debounce delay - there are a few options larger than 90ms please see the register below with relevant options highlighted:
The larger debounce delay will give more margin to fully insert the jack and give better readings. I do think this is the most likely issue since your customers accuracy increases with faster insertion times. Changing this register with a larger delay will give more time for a full insertion.
2. However there is another possibility that could also be affecting detection. There are a few edge cases that aren't detected properly by the device. During detection the device sends a a signal from tip to ring2 and from tip to sleeve. It then takes those values and assigns them a 3 digit code based on the impedance. One important note is that the device saturates after 2800 Ohms - and 10K ohms will me measured to be equal to 1M ohms because of this. After it has its two impedance values it compares them with the following results:
R(tip to sleeve) = R(tip to ring2) --> 3-pole headset detected
R(tip to sleeve) > R(tip to ring2) --> Standard 4-pole headset detected
R(tip to sleeve) < R(tip to ring2) --> OMTP 4-pole headset detected
Improper detection can occur if one of the two following scenarios occur:
I do think it is more likely scenario 1 - and increasing the debounce time should help with detection. However there are a few edge cases that can be hard to detect and if issues are still arising it may be a mismatch of accessory impedances or accessory with the audio jack that is being used - however I do think this is unlikely.
If you have any other questions please let me know!
Best,
Parker Dodson
