Credit Card Reader Questions (Square, Paypal, Intuit) - Sony Xperia P, U, Sola, Go

Has anybody here had any luck using one of those credit card readers? I can tell you that I have tried the Square reader and Paypal here reader and both do not work with my Xperia U St25a ICS ROM. I am still waiting for the Intuit in the mail but chances are that it is not going to work either.
After searching multiple forums, some blame it on the hardware, but also some users report it working after changing their rom. Some users also report it working after an update from the software developer.
The issues seem inconsistent. I am thinking it can be a possible sound level issue. Maybe the microphone input from the square reader into the headphone jack is getting distorted.
What do you think may be the problem?
Update 10am:
I did an audio comparison with the square reader on each of my two devices. The Xperia U that does not read the credit cards in the software, and a Lenovo Thinkpad Tablet that does. I used Easy Sound Recorder as the recording app. And after getting two samples, I uploaded them to Audacity.
As you can see, there is a difference in sound output. The first row is from the Xperia U, and the second row is from the Thinkpad. They both produce the same pattern.
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I attempted this with the Paypal here reader, but it seems to only work once it hears a certain sound from the actual paypal here application.
Update 11:45am:
I had my old HTC ChaCha laying around which also works with the Square reader. I found something interesting... Notice how the sound peaks more than the Xperia U. So I don't exactly think its a distortion issue. However when listening to the sound samples. The Xperia U has a very muted sound compared to the Thinkpad and Chacha, as if some of the treble was restricted. There is a sound of clarity coming from the Thinkpad and Chacha sound samples.
So my new question is... Is there a way to adjust the microphone levels to get this reader working?

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My credit card reader of PagSeguro also does not work on my Xperia P

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i know this is an old topic but i've been doing some investigating into this myself.
the difficult thing is two-fold. first, documentation on which android phones and tablets that have the TRRS 3.5mm jack does not seem to exist. i've posted the question in several forums, but nobody has yet to reply. So short of contacting every android manufacturer, i doubt i'll be able to get the necessary information to influence which device i buy.
second problem comes from these mobile cc companies themselves.
lets take square for example. here is their list of 'compatible' android devices
pretty poor if you ask me. in fact, the list of devices with problems far outweigh the list of devices that actually work! https://squareup.com/help/en-us/article/3887-features-and-device-compatibility
but even worse is "paypal here". they basically have no android device list at all but just offer a suggestion to 'try and see if it works!' https://www.paypal.com/webapps/mpp/paypal-here-compatible-devices
at least intuit gopayment has a decent list http://kbgopayment.intuit.com/intuit/index?page=gopayment_content&id=INF16030
another one that i found was from a company called magtek. they have several mobile cc readers, one called the udynamo. they too have a decent list, but mostly are just phones http://www.magtek.com/v2/forms/udynamo-compatibility.html

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Solution?
Hi!
Maybe in this video there is a solution for this. I think that the problem is regarding the microphone sensibility.
Try it!
search at youtube this:
"Solucion problema comunicación mPos de TodoPago"
thanks!