This thread has been locked.
If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.
Hello,
I'm using a ADS1203IPWT as a Delta-Sigma Modulator, which is configured to run in Manchester mode.
According to the Datasheet of ADS1203IPWT the frequency can vary between 8.7 to 11 MHz.
I use the SDFM of the TMS320F28379D to demodulate the signal. I had the weird behavior, that with one ADS1203IPWT everything worked fine and with another I got almost random values from the SDFM.
After long research I figured out, that the TMS320 has a Data Cycle time (SDx_Dy) from 8 - 20 times of the system frequency. So, running the TMS with its normal frequency of 200MHz I get a range of 25-10MHz, which is allowed as Manchester input frequency. So, if the Delta-Sigma Modulator is at room temperature its frequency is around 9.95MHz and the SDFM does not work! If I cool it down to -10°C the frequency rises to 10.3MHz and everything is ok. I tested it even with reducing the System Frequency of the TMS to 100MHz resulting in a range of 12.5-5MHz of Delta-Sigma Modulator frequency and it worked even on room temperature.
The specification of SDFM of TMS doesn't make sense to me. Why you limiting the frequency to 10MHz at normal system frequency?
Is there any hidden bits, which will support lower frequencies? 10MHz is the normal frequency for any Manchester Coded signal, so the SDFM is useless if it does not support around 10MHz.
Do you have any work around for that?
Best Regards,
Stefan
Stefan,
You're right, Manchester mode works correctly only when SDFM Timing Requirements is met. There are no additional hidden bits available to make it work at lower frequencies.
Based on the SDFM Manchester mode timing requirement SD-Cx frequency should be 10 - 25 MHz for Manchester mode to work properly.
Regards,
Manoj
Then the question, do you have a pin compatible Sigma Delta Modulator to the ADS1203IPWT, which runs at 20MHz? I couldn't find one.
Stefan,
See whether AMC1306 option would fit you. I would also suggest you to contact the associated team responsible to check whether this unit would be correct choice for your application.
Regards,
Manoj