The invention relates to a high-precision simple A / D converting circuit and a method based on MSP430. The invention adopts the P2.0 port of the MSP430 to be externally connected with a
resistor and a
capacitor which are serially connected; the other end of the
resistor is connected with the P2.3 port of the MSP430, the other end of the
capacitor is connected to the power supply ground. An
analog signal is connected to the P2.4 pin of MSP430F1121 to form a sigma-
delta resembling type single-slope A / D converter. The
conversion method is realized by that a half of the
total count value N / 2 is loaded at first, and whether the output of a
comparator is high level is determined, if yes, the P2.0 outputs low level; if not, the P2.0 outputs high level; the count value of the high level adds 1, the
total count value N / 2 deducts 1, whether the
total count value N / 2 is 0 is judged, if not, then the step is skipped previous, if yes, the P2.3 and the P2.4 pins are exchanged internally, and then the measurement sub-program is over. The invention solves the problem that the over-sampling sigma-
delta conversion is applied due to the characteristic of
high resolution, but the over-sampling sigma-
delta conversion has complex structure, large volume, and hard operation. The invention achieves the effects that the
conversion method is simple, the circuit structure is simplified, the volume is small, the cost is low, and the method can be easily implemented.