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#!/usr/bin/env python3
###
# Dependencies: Linux, python3, python3-smbus
# Usage: `sudo ./set_lp8550_slope.py`
#
# Default slope is 0b101=200ms, can be adjusted below
# Tested with Ubuntu 20.04 on A1466 2013
# All original EEPROM registers value:
# - A0: 0b01111111
# - A1: 0b10110101
# - A2: 0b10111111
# - A3: 0b01111011
# - A4: 0b00101000
# - A5: 0b11001111
# - A6: 0b01100100
# - A7: 0b00101101
###
import smbus
import time
config = {
'smbus_address': 0, # SMBus address, can use `i2cdetect -l` to find it
'device_address': 0x2C, # LP8550 7 bits address
'slope': (1, 0, 1) # The new slope to set, MSB first, see lp8550 datasheet 8.6.2.3 SLOPE
}
lp8550_regs = {
'EEPROMControl': 0x72,
'EEPROMAddress1': 0xA1 # default value for this register is 0b10110101 on original 820-3437
}
def bitstolist(val, regsize=8):
return [(val >> i) & 0b1 for i in range(0, regsize)]
def listtobits(l, regsize=8):
val = 0
for i in range(0, regsize):
val += l[i] << i
return val
def read_reg(bus, dev_address, reg_name):
return bitstolist(bus.read_byte_data(dev_address, lp8550_regs[reg_name]))
def write_reg(bus, dev_address, reg_name, reg):
print(f'Writing { listtobits(reg)} to {dev_address}, {lp8550_regs[reg_name]}')
bus.write_byte_data(dev_address, lp8550_regs[reg_name], listtobits(reg))
def get_slope(bus, dev_address):
return read_reg(bus, dev_address, 'EEPROMAddress1')[0:3][::-1]
def set_slope(bus, dev_address, slope):
print('Original slope: ', get_slope(bus, dev_address))
EEPROMAddress1 = read_reg(bus, dev_address, 'EEPROMAddress1')
EEPROMAddress1[0:3] = slope[::-1]
write_reg(bus, dev_address, 'EEPROMAddress1', EEPROMAddress1)
print('New slope: ', get_slope(bus, dev_address))
def write_nvm(bus, dev_address):
print('Writing to non-volatile memory')
EEPROMControl = [0]*8
EEPROMControl[2] = 1 # EE_INIT=1
write_reg(bus, dev_address, 'EEPROMControl', EEPROMControl)
EEPROMControl[1] = 1 # EE_PROG=1
EEPROMControl[2] = 0 # EE_INIT=0
write_reg(bus, dev_address, 'EEPROMControl', EEPROMControl)
time.sleep(0.2) # wait 200ms
EEPROMControl[1] = 0 # EE_PROG=0
write_reg(bus, dev_address, 'EEPROMControl', EEPROMControl)
def load_nvm(bus, dev_address):
print('Loading from non-volatile memory')
EEPROMControl = [0]*8
EEPROMControl[2] = 1 # EE_INIT=1
write_reg(bus, dev_address, 'EEPROMControl', EEPROMControl)
EEPROMControl[0] = 1 # EE_READ=1
EEPROMControl[2] = 0 # EE_INIT=0
write_reg(bus, dev_address, 'EEPROMControl', EEPROMControl)
time.sleep(0.2) # wait 200ms
EEPROMControl[0] = 0 # EE_READ=0
write_reg(bus, dev_address, 'EEPROMControl', EEPROMControl)
def main():
bus = smbus.SMBus(config['smbus_address'])
set_slope(bus, config['device_address'], config['slope'])
write_nvm(bus, config['device_address'])
load_nvm(bus, config['device_address'])
print('Slope in non-volatile memory: ', get_slope(bus,config['device_address']))
if __name__ == "__main__":
main()
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