Hi, when using the WT-32i as an audio SINK the audio polarity coming out of pins 46,47,49,50 is correct.
When I use it as a SOURCE and inject audio into the input pins 41,42,44,45 and measure on the output of a Bluetooth receiver then the polarity is reversed.
Is this by design? I do see that the P and N indication on the data sheet are in a different order for the inputs compared to the outputs. In other words:
for Output 46 is N, 47 is P
for Input 41 is P and 42 is N
is it possible the datasheet is mislabeled? I realize that for normal listening it really isn't audible, but we are trying to fulfill a design spec that calls it out. If need be we can swap our traces but would like to know if this is a known or intentional issue.
yes i faced to this issue too. N and P polarity is not consistent across datasheet. For example Figure 21: Single-ended speaker connection indicate to connect the speaker to P, but in Figure 32: Example schematic it´s connected to N.
Could you please describe me how do you exactly check if the polarity on the output is reversed? Do you check some characteristic points of the signal? It is possible that reverse effect is signal which is shift in phase (due to delay between sent and received it on the remote side). If you e.g. transmit some sinusoidal signal then this signal, which is shift in phase on the receiver side, can look like "reverse" effect.
Have you got loopback or Bluetooth connection?
Figure 21 should be treated as an example of speaker connection. It is not mandatory to always connect it exactly in the same way.
We use a polarity check signal from a phone. First look at the signal from the headphone jack. 4 pulses, down down down up. then we connect to the Bluetooth and put the scope on the output with + of he scope to the P pin on the BT module. Then we see up up up down. Not related to the delay because of the pulse design. Can you confirm this at your side?
Reference to Hynek observation, indeed your data sheet shows on Fig 32 the headphone output tip and ring are connected to N, where Fig 33 Tip and Ring connect through the external amplifier to P. As I mention I realize it doesn't really matter for sound quality, but we do need to confirm our result for our documentation. If the answer is that it is simply mis-labeled or designed to be inverted then that's fine.
>Can you confirm this at your side?
This issue is not known for me, although I suppose that it could be connected with output-stage design and how do you exactly measure it.
As I understand you have got your own hardware, is that correct? Could you please provide us your output-stage schematic for verification?