Bitwise_operations.ipynb

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    "# Checking and manipulating individual bits in Python\n",
    "\n",
    "In the Advanced Labs Python is used for interfacing and experiment control and some experiments (in particular the Stage 3 Surface Plasmons experiment) need manipulation of individual bits.\n",
    "\n",
    "Python lets you print numbers in binary to see individual bit values and has a whole range of bitwise operations.\n",
    "\n",
    "\n",
    "| Operation | Symbol | \n",
    "|-----------|--------|\n",
    "| Bitwise AND | &    |  \n",
    "| Bitwise OR |  \\| | \n",
    "| Bitwise NOT |  ~ | \n",
    "| Bitwise XOR |  ^ |\n",
    "| Bitwise shift left | << |\n",
    "| Bitwise shift right | << |\n",
    "\n",
    "Here are some examples:"
   ]
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     "text": [
      "b has value 57 (decimal) and 00111001 (binary)\n"
     ]
    }
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   "source": [
    "# create and bring a binary number 00111001:\n",
    "\n",
    "b = 0b00111001\n",
    "print(f\"b has value {b:} (decimal) and {b:08b} (binary)\")"
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     "text": [
      "00001000\n",
      "Yes - that bit is set!\n"
     ]
    }
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    "# check if bit 3 (counting from 0) of b is high or low\n",
    "#\n",
    "# to do this we will Bitwise AND with 0x00001000\n",
    "\n",
    "print(f\"{ b & 0b00001000 :08b}\")\n",
    "\n",
    "# since this is a non-zero value and has a boolean equivalent of True,\n",
    "# we can make a logical decision using it:\n",
    "\n",
    "if b & 0b00001000:\n",
    "    print(\"Yes - that bit is set!\")\n",
    "else:\n",
    "    print(\"No = that bit is not set!\")"
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     "text": [
      "00000001\n",
      "00000010\n",
      "00000100\n",
      "00001000\n",
      "00010000\n",
      "00100000\n",
      "01000000\n",
      "10000000\n"
     ]
    }
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   "source": [
    "# here is an example of using bitshift:\n",
    "\n",
    "b = 1\n",
    "\n",
    "for i in range(8):\n",
    "    print(f\"{b:08b}\")\n",
    "    b = b << 1\n"
   ]
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   "cell_type": "code",
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     "text": [
      "b before: 00000001\n",
      "b after:  00010001\n"
     ]
    }
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   "source": [
    "# Example: using bitwise OR to set a bit to 1\n",
    "\n",
    "b = 0b00000001\n",
    "\n",
    "print(f\"b before: {b:08b}\")\n",
    "\n",
    "b = b | 0b00010000\n",
    "\n",
    "print(f\"b after:  {b:08b}\")"
   ]
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     "text": [
      "b before: 10010001\n",
      "b after:  10010000\n"
     ]
    }
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    "# Example: using bitwise AND to set a bit to 0\n",
    "\n",
    "b = 0b10010001\n",
    "\n",
    "print(f\"b before: {b:08b}\")\n",
    "\n",
    "# we will only set the least significant bit to 0 \n",
    "# and leave all other bits unchanged\n",
    "b = b & 0b11111110\n",
    "\n",
    "print(f\"b after:  {b:08b}\")"
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      "10010001\n",
      "10010000\n"
     ]
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   "source": [
    "# Making code readable\n",
    "#\n",
    "# Code readability can be improved by using variables and Bitwise ORing them together.\n",
    "# Example: say bit 4 is to enable a motor, bit 8 sets the direction\n",
    "# and it is stepped by making bit 0 low then high (clock steps) with the clock\n",
    "# pulse requring a minimum of 100 ms high and low\n",
    "\n",
    "from time import sleep\n",
    "\n",
    "def write_data(bits):\n",
    "    \"\"\"Dummy function to sumulate writing to hardware but just prints binary\"\"\"\n",
    "    print(f\"{bits:08b}\")\n",
    "\n",
    "enable = 0b00010000\n",
    "dir_cw = 0b10000000\n",
    "dir_ccw = 0b00000000\n",
    "clock_high = 0b00000001\n",
    "clock_low = 0b00000000\n",
    "\n",
    "\n",
    "# to move one step in CW direction\n",
    "write_data(enable | dir_cw | clock_high)\n",
    "sleep(0.1)\n",
    "write_data(enable | dir_cw | clock_low)\n",
    "sleep(0.1)\n",
    "\n",
    "# functions can be made to make the code very readable and user friendly"
   ]
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