type
  MQTTByte = uint8

proc MQTTByte(x: uint8): MQTTByte =
  result = MQTTByte()
  result.cont = x and 1 #Extract continue bit
  result.bit =  x and uint8.high - 1 #Get data bits

...
var varValue = 276
varValue = (varValue / 128).uint8.MQTTByte #redefinition of 'MQTTByte';