Other Parts Discussed in Thread: TMS320F28377S, C2000WARE
I use four AMC1303E2520 to measure isolated voltage, as described in chapter 9.2.2 of the AMC1303 datasheet. There is the R3’ = R3 resistor, and no input filter. The Manchester signals are decoded with the SDFMs of a TMS320F28377S. My problem is that I get inverted results on all four channels. That means that a positive measured voltage gives a negative result in software and vice-versa. There is no noticeable offset. For instance, +100V = -4000 and -100V = +4000.
In the same way, the comparator units are working upside down. For example, with a full scale of 32768, +100V = 10384 and -100V = 22384. A side effect of this is that the high and low threshold registers are inverted too. For a high threshold at +50V, I have to set SDCMPLx = 13384 and for a low threshold at -75V, SDCMPHx = 20884.
The code is a modified version of a C2000Ware SDFM example. I have checked that the positive and negative input of the AMC1303 are not inverted in the schematic and on the PCB.
I am sure that I miss something, but I cannot figure what. Can anybody help me?
Thank you very much and best regards