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""" Maxim Integrated Products MAX5477 Dual, 256-Tap, Non-volatile, I2C-Interface, Digital Potentiometers


"""

# The MAX5477 has a total end-to-end resistance of 10kΩ.
# The devices feature an internal non-volatile EEPROM(NVREG) used
# to store the wiper position for VREG initialization during power-up.
# A write-protect feature prevents accidental overwrites of the EEPROM.

# 2023-01-29 
# Auther: kimi
# ( kimiyo7819@gmqil.com )

# tested on MicroPython v1.19.1 on 2022-06-18; Raspberry Pi Pico with RP2040
# modified for Seeeduino XIAO on 03/08/2023

# 2023-05-26
# Currently the code is fragile with write operations to store values
# in non-volatile memory. I'm investigating the cause of this instability
# and looking for a solution. 

# Note that writing to volatile memory is working as expected.

# 2023-05-28
# The unstable behavior observed is a result of the write operations
# to non-volatile memory taking longer than expected,
# leading to data loss when consecutive write commands are executed.
# To achieve stability, I have introduced a waiting time. Currently,
# I have set it to 100 msec temporarily, but it seems that a waiting
# time of 10 msec is insufficient.

# Unfortunately, I could not find this information in the datasheet.
# It's possible that I may have overlooked it.

# 2023-05-29
# Non-volatile memory write busy time is 12 ms. This was documented
# in the provided datasheet in the table "Timing Characteristics".
# Changed the Waiting time setting to 20 ms.

import time

# Seeeduino XIAO requires soft I²C
#from machine import Pin, SoftI2C

#SCL = 7
#SDA = 6

# Raspberry Pi Pico
from machine import Pin, I2C

SCL = 1
SDA = 0

op = {"R0": 0b0001,
      "R1": 0b0010
      }

reg = {"write_VREG":  0b0001_0000,
       "write_NVREG": 0b0010_0000,
       "copy_NVtoV":  0b0110_0000,
       "copy_VtoNV":  0b0101_0000
       }

class MAX5477:
    
    def __init__(self, addres=0x28):

        # Seeeduino XIAO
        #self.i2c = SoftI2C(scl=Pin(SCL), sda=Pin(SDA), freq=100000)
        # Raspberry Pi Pico
        self.i2c = I2C(0, scl=Pin(SCL), sda=Pin(SDA), freq=100000)

        self.MAX5477_Addr = addres

        # MAX5477 has 3 pins for address
        # # Slave Addresses

        # A2  A1  A0
        # GND GND GND 0b0101000(0x28)
        # GND GND VDD 0b0101001
        # GND VDD GND 0b0101010
        # GND VDD VDD 0b0101011
        #       ...
        # VDD VDD VDD 0b0101111
        
    def command(self, command="write_VREG", operation = "R0", value=125):
        """ Set command & value to MAX5477

        Args:
            command (str, optional): write or copy a value to volatile or non-volatile memory. Defaults to "write_VREG".
            operation (str, optional): Select either resistor R0 or R1. Defaults to "R0".
            value (int, optional): a data bytes. Defaults to 125.

            Write protection(WP) changes the behavior.
        
            WP=0 (connect to GND)
                write_VREG:  I2C data is written to VREG.
                        Wiper position updates with I2C data.
                        No change to NVREG.
                    
                write_NVREG: No change to VREG or wiper position.
                        I2C data is written to NVREG.
                    
                copy_NVtoV:  Copy NVREG to VREG.
                        Wiper position updates with NVREG data.
                        No change to NVREG.
                        
                copy_VtoNV:  Copy VREG to NVREG.
                        No change to VREG or wiper position.
                        
            WP=1 (connect to VDD)
                write_VREG:  Copy NVREG to VREG.
                        Wiper position updates with NVREG data.
                        No change to NVREG.
                        
                write_NVREG: No change to VREG or wiper position.
                        No change to NVREG.
                        
                copy_NVtoV:  Copy NVREG to VREG.
                        Wiper position updates with NVREG data.
                        No change to NVREG.
                        
                copy_VtoNV:  No change to VREG or wiper position.
                        No change to NVREG.
        """
        cmd = reg[command] | op[operation]
        self.i2c.writeto_mem(self.MAX5477_Addr, cmd, bytes([value]))
        
        time.sleep_ms(20)
            
if __name__ == '__main__':
    
    # Test assuming op amp operation
    
    register = MAX5477(0x28)
    
    # writing data to non-volatile memory.
    # offset
    register.command("write_NVREG", "R0",100)   
    # amplification
    register.command("write_NVREG", "R1", 98)
    
    # copy non-volatile memory to volatile memory.
    # offset  
    register.command("copy_NVtoV", "R0", 0)
    # amplification
    register.command("copy_NVtoV", "R1", 0)