From the narrative earlier you my have worked out we can no longer just write a value to a buffer and expect the digit we require to magically appear in a soft LED glow. No, the value of 0x5B we were using in our example must now be split across all 8 buffers (each buffer represents the same segment across all of the digits). I’ll use the value 2013 to demonstrate. In binary and hex the digits are represented as follows

Now we transform it to represent the data as it needs to be written to the buffers for common anode displays

a0-a3 = digits 1-4 respectively

To achieve this I took the Adafruit_SevenSegment.py file and reworked it to my needs.  Firstly I added some bit flipping code from here https://wiki.python.org/moin/BitManipulation

  # setBit() returns an integer with the bit at 'offset' set to 1.
  def setBit(self, int_type, offset):
    mask = 1 << offset
    return(int_type | mask)

  # clearBit() returns an integer with the bit at 'offset' cleared.
  def clearBit(self, int_type, offset):
    mask = ~(1 << offset)
    return(int_type & mask) 

Added a function to control an individual segment

  def setSegState(self, anode, cathode, state):
    rowBuffer = self.disp.getBufferRow(cathode)
    if (state==False):
        rowBuffer = self.clearBit(rowBuffer, anode)
    else:
        rowBuffer = self.setBit(rowBuffer, anode)
    self.disp.setBufferRow(cathode, rowBuffer, True)

Then reworked the writeDigitRaw function to use them

  def writeDigitRaw(self, charNumber, value):
    "Sets a digit using the raw 16-bit value"
    if (charNumber > 15):
      return
    # Set the appropriate digit, pad to 8 binary digits
    valueBin = bin(int(value))[2:].rjust(8,'0')
    row = len(valueBin) - 1
    for digit in valueBin:
      self.setSegState(anode=charNumber,cathode=row,state=(digit=='1'))
      row-=1

I had now recreated the ability to reference a digit and provide a hex representation of the segments that needed to be shown.

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