set_lp8550_slope.py

#!/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()