An experimentation of the software PLL for power grid frequency with raspberry pi pico. Ported from TI's "Software PLL Design Using C2000".
Pin assign is here:
| AC input(*) | GPIO26 |
|---|---|
| 8fo | GPIO16 |
| 4fo | GPIO17 |
| 2fo | GPIO18 |
| fo | GPIO19 |
| /fo | GPIO20 |
| where fo is SPLL output. |
The program assumes AC input frequency is 50Hz. It can be changed the line
#define GRID_FREQ 50
in grid_spll/main.c. AC input given to ADC CH0 pin (GPIO26) is assumes ~1Vp-p offseted ~2V. One can set the offset voltage with changing the line
#define AC_INPUT_OFFSET 0x981
appropriatly. For example, 1.65v offset can be set with
#define AC_INPUT_OFFSET 0x800
The program uses TI's 32-bit fixed point arithmetic library IQMath in mspm0-sdk which is given as a git submodule.