Yes, I'm trying to do this while the main core is in deep sleep. But if it can't be done in deep sleep, what is de point of de SLEEP command? And do you know of an other way to change the sleep time while in deep sleep?

In the technical reference manual their is a figure (157) showing the change of the sleep cycles for the ULP. I't states its using the SLEEP command. When I try to change the SLEEP_CYC_REG, it still uses REG0, not REG1. I set the register in the main program with: ulp_set_wakeup_period(0, 250 * 1000...