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mpc5744 Adc sampling inaccurate

Question asked by Chen bingen on Dec 9, 2018
Latest reply on May 14, 2019 by Peter Vlna

MPC5744P chip ADC sampling, the reference voltage is 5V ,ADC0 and ADC1 sampling port peripheral reference voltage circuits are the same. The software is configured with ADC0 port 0 channel, ADC1 port 0 channel sampling at the same time, the external input analog voltage has 0 ~ 5 V change; Phenomenon: ADC0 port 0 channel sampling is normal, external voltage 2.5 V shows AD value 2045; When the external voltage of the ADC1 port 1 channel is 2.5V, the AD value 1750A DC0 changes linearly with the external voltage analog signal, and the ADC1 changes linearly with the external voltage analog signal (0 v corresponding to AD value 0 V to 5 v to AD value 4095, intermediate nonlinearity).

May I ask which points may have caused this phenomenon to occur?