Effective ADC bit (ENOB) is about 1.5 to 2 less than the specification? 8 bit ADC has 6 bit real accuracy and resolve 64 steps of digital SPI signal. Would that be enough for task below?
How much sampling rate do I need to see the signal, without risk of missing some short time glitch? SDS2104 is 1GSa/s when all 4 ch activated, right? For 20MHz SPI clock, 50 dots per cycle. Enough?
On speed alone, Rigol MSO5074 is exceptional high 8GSa/s for 700 UK pounds.
I need the tool to do proper design verification after MCU software function ok.
Look at analogue waveform of signal sent between MCU and external chip over SPI. Verify data sheet setup time, hold time. Also, signal integity. Smooth rise fall of signal. No ringing, overshoot, undershoot.
Catch any rare occurrence signal that can fail the system once in, says, every 100 hours running. Says, "poor" power supply voltage dropped when multiple loads are switched at same time due to rare situations/software event.