PSP Oscilloscope

Jai_Guru · Post by **Jai_Guru** » Mon Jan 15, 2007 6:55 pm

I would like to use my PSP as an oscilloscope by connecting the input voltage to the analog audio input. The main use of this would be to make measurements on micro controller circuits with TTL voltage levels (6V-0V).

Does somebody know what is the range of voltages supported by the audio input?

Has somebody developed something similar?

MrMr[iCE] · Post by **MrMr[iCE]** » Tue Jan 16, 2007 4:11 pm

I think your 'scope' would be limited to sampling at 44kz, the only frequency it can record at (I think, someone correct me if I'm wrong). You'd need something a bit more realtime, possibly through the usb port.

Jai_Guru · Post by **Jai_Guru** » Tue Jan 16, 2007 4:53 pm

I'm not sure about USB, hardwarewise it gets much more complicated.

My aim is to analyze the signals sent by a keyboard, pulses sent to a servo motor to control it or maybe signals sent on serial communication.

This signals operate at frequencies lower than 44kz so I don't think this would be a problem.

Jai_Guru · Post by **Jai_Guru** » Wed Jan 31, 2007 4:33 pm

What circuit do I need to build to connect 5v TTL signals to the audio input of my PSP and not ruin it?

avisx · Post by **avisx** » Wed Jan 31, 2007 10:06 pm

good idea, ;)

memon · Post by **memon** » Wed Jan 31, 2007 10:39 pm

There are some projects around the web which purpose is to turn a pc sound card into a oscilloscope. Google: pc sound card oscilloscope

You will need some special electronics to convert the signal to nice range for the sound card (or psp) to record. You will run into a problem trying to measure DC voltages, though, because there is usually a capacitor in the input before the ADC.

This might be a good starting point:
http://xoscope.sourceforge.net/

Jai_Guru · Post by **Jai_Guru** » Thu Feb 01, 2007 3:07 am

Thanks for the reply.

Sorry, but i'm not very experienced with hardware.

You will run into a problem trying to measure DC voltages, though, because there is usually a capacitor in the input before the ADC.

As I said before, the main use i want to give this is to measure signals from microlcontrolers so I need to measure DC voltages.

To fix this could I modulate the input signal somehow and then demodulated using software?

Jai_Guru · Post by **Jai_Guru** » Thu Feb 01, 2007 4:34 pm

I found this page that could be useful.

http://www.qsl.net/om3cph/sb/dcwithsb.htm

It explains the problems of using a sound card to measure DC signals. I haven't finished reading it but it looks like a valuable resource.

Jai_Guru · Post by **Jai_Guru** » Thu Feb 01, 2007 5:34 pm

My next question will be a bit off topic but I hope it's not a big problem.

I found an old sound card and I wonder if I could avoid the DC measuring problem by removing and bypassing the capacitors right next to the line in and mic plug.

Any opinions?

Jai_Guru · Post by **Jai_Guru** » Sat Feb 03, 2007 3:11 am

I think what a want it's not an Oscilloscope but a logic analyzer.

I'm only interested on binary voltage levels.

Is there a way to know if a pin on USB or Serial Port is high or low?

what other method of input could be used?