Checking arduino code with multimeter -

when upload code on arduino ,sometimes not desired results. saw friend of mine doing test on arduino using multimeter make sure code right.

he said can make sure code right checking voltages on carious i/o pins on arduino. if voltage on i/o pins less 5 v code having error,and if chckt voltage on rx , tx pins should 0.29 v.

i know question posted me not clear, worked not able understand properly.

so if can deduce means , how done so, please proide answer?

there 2 main things test multimeter: voltage of power arduino (between 5v , gnd), , voltage of io pins (between them , gnd).

• voltage of power supply tells if arduino powered correctly, if power management circuits or power supply have failed, you'll able pick here.
• voltage of outputs should either 5v or 0v, relative ground. testing voltage on pin can tell whether being written high (5v) or low (0v) arduino, hence seeing code doing pins.

i should make clear there no right or wrong way tell if code in general working based on voltage of pins.