Picomite Phase Correct PWM

Author	Message
robert.rozee Guru Joined: 31/12/2012 Location: New Zealand Posts: 2542	Posted: 11:38am 27 Aug 2022         Volhout said   [...] Maybe it is better to add a 4'th parameter to the PWM command, that when not used keeps the standard mode. i.e. PWM frequency, duty cycle A, duty cycle B, "P" I have seen that many PWM's have this "phase correct" feature, so it could even become a standard extension of MMBasic. Volhout the downside with an extra parameter is that it requires additional complexity in the interpreter to decode it: distinguishing between a letter ("P") and a number, generating an error if it is the wrong letter, etc. in the case of the MX170 at least, there is almost no spare flash available for this sort of thing. a negative frequency, on the other hand, can be checked with just a couple of machine code instructions. then a couple or three more instructions to divide the frequency by -2, and a single poke to change the PWM configuration register. potentially it may only involve growing the firmware by a handful of bytes - a far smaller barrier when flash space is scarce. it also means the new feature can be 'silently slipped in' without needing to document it   cheers, rob   :-)