lpc 2148 input signal frequency

[aniket433]

Hello i trying to make oscilloscope using lpc 2148..

1)what would be the maximum 'digital signal' frequency i can apply at the inputs of lpc 2148 for proper processing?

2)As said in datasheet, for 10 bit ADC max sampling rate is 400 kSPS so what sampling rate should i take for proper regeneration of input 'analog signals' on display?
or
if i set the sampling rate at 400ksps what would be the max. analog signal frequency i can allow at the inputs of adc for proper regeneration?

 

[pinout]

My thoughts are:

If you were looking at doing fft to see frequency content then the theory is >2 points per cycle so that would resolve upto 200kHz.
But for actual waveform display you need 10 or more points to see a nice sinewave clearly, so up to 40kHz would be useful.
And another 'But'! If you want good squarewaves and be able to see ripple and overshoot need even more points.......

Lots of USB scopes often only have 8bit ADC's so that they can do higher speed acquisitions.

Don't forget you need to band limit your input frequency range to avoid aliases and this can be quite a tricky compromise with sample rate.

 

[aniket433]

thanks... what about digital signals( logic analyzer)? what max. bandwidth i can achieve for digital signals? ( if i applied digital signals directly to the inputs of microcontroller, not to adc.)