beaglebone PWM

pwm.py

from mmap import mmap 
import struct 

MMAP_OFFSET = 0x44c00000                # base address of registers 
MMAP_SIZE   = 0x48ffffff-MMAP_OFFSET    # size of the register memory space 

CM_PER_BASE = 0x44e00000 - MMAP_OFFSET 
CM_PER_EPWMSS1_CLKCTRL = CM_PER_BASE + 0xcc 
CM_PER_EPWMSS0_CLKCTRL = CM_PER_BASE + 0xd4 
CM_PER_EPWMSS2_CLKCTRL = CM_PER_BASE + 0xd8 

with open("/dev/mem", "r+b") as f: 
    mem = mmap(f.fileno(), MMAP_SIZE, offset=MMAP_OFFSET) 

def _andReg(address, mask): 
    """ Sets 32-bit Register at address to its current value AND mask. """ 
    _setReg(address, _getReg(address)&mask) 

def _orReg(address, mask): 
    """ Sets 32-bit Register at address to its current value OR mask. """ 
    _setReg(address, _getReg(address)|mask) 

def _xorReg(address, mask): 
    """ Sets 32-bit Register at address to its current value XOR mask. """ 
    _setReg(address, _getReg(address)^mask) 

def _getReg(address): 
    """ Returns unpacked 32 bit register value starting from address. """ 
    return struct.unpack("<L", mem[address:address+4])[0] 

def _setReg(address, new_value): 
    """ Sets 32 bits at given address to given value. """ 
    mem[address:address+4] = struct.pack("<L", new_value) 

_setReg(CM_PER_EPWMSS1_CLKCTRL, 0x2)