S12G ADC SYNC

[fanziyu]

Hi folks!

Is there a way with the S12G128 to sync or trigger an ADC sample & conversion from the start of the PWM period?

PWM Frequence is 20k

I use HalfBridge to control a brush DC by PWM and need measure the current ,the current sense is a square wave(20k) .

Is there a clever way to solve the problem ? it is too late for me to change the chip.

Thanks

[lama · Accepted solution]

Hi,

Yes, there is internal HW connection between PW0 and ETRIG0, PWM1 and ETRIG1, etc ...   Please check chapter 2.6.4 ADC External Triggers ETRIG3-0 in reference manual (page 254,255). If PWM is enabled, ETRIG will be driven by PWM (internally or trough pin).  Since PWM outputs in 16-Bit Mode are PWM1, PWM3, PWM5 and PWM7, only two internal links 
ETRIG1 and ERIG3) could be used of ADC triggering.  I would like to recommend in your case external link from PWM outputs into some of remaining 
port AD inputs (ETRIGSEL=0, ETRIGCH[3:0] refers to appropriate PAD input). For more details please see Table 11-5. External Trigger Channel Select Coding (page 427).   Best regards,
Ladislav