21-09-21 LC01.ipynb

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    "# Introduction to Verilog programming on an FPGA device. Counters and frequency dividers.\n",
    "\n",
    "## Laboratory Class 01 - 21 September 2021\n",
    "\n",
    "\n",
    "### Topics\n",
    "- A short overview of FPGA devices and HDL programming languages.\n",
    "- Introductory problem: design of a 1 Hz counter with 8–LED array display, relying on standard analog and digital circuitry and an 8 Hz clock source.\n",
    "- Basic hardware circuits:\n",
    "    - frequency divider;\n",
    "    - counter.\n",
    "- Verilog programming language:\n",
    "    - module architecture;\n",
    "    - example: development of an 8–bit, 1 Hz counter with an 8–LED array display;\n",
    "    - basic modules implementing basic hardware circuits:\n",
    "        - frequency divider;\n",
    "        - counter.\n",
    "\n",
    "### Problems:\n",
    "- development of an 8–bit, 1 Hz counter with an 8–LED array display, working from 0 to 255;\n",
    "- development of an 8–bit, 1 Hz counter with an 8–LED array display, working from 0 to 9;\n",
    "- development of an 8–bit, 10 Hz counter with an 8–LED array display, working from 0 to 9.\n",
    "\n",
    "### Additional problems:\n",
    "- development of a 10 Hz counter, working from 0 to 99, with a 2–digits BCD[^bcd] coding and a 2 x 4–LED array display;\n",
    "- development of a 10 Hz down counter.\n",
    "\n",
    "---\n",
    "\n",
    "```{admonition} Disclaimer\n",
    "This part of the note does NOT aim to teach Verilog or how to survive in a laboratory. The first can be learned using apposite websites like [hdlbits](https://hdlbits.01xz.net/wiki/Main_Page) while the second skill requires years of training and struggle. The only way to learn how to survive in a laboratory is to be in a lab. It doesn't need to be an expensive one tho. To start a [beginner's FPGA](https://www.nandland.com/goboard/introduction.html) and a [basic oscilloscope](https://espotek.com/labrador/) are enough[^disclaimer]. In the worst-case there even exist simulators. Better than nothing, I guess.\n",
    "```\n",
    "\n",
    "[^bcd]: Binary coded decimal. Each digit is represented using four LEDs; they are placed in a decimal representation. e.g: $34$ would be written as 0011 0100 in BCD. \n",
    "[^disclaimer]: I studied Verilog on hdlbits but I do not own the GoBoard or the EspoTek Labrador Board so I can not say anything about their quality. These are just linked to helping you start your researches\n",
    "\n",
    "\n",
    "## Basic hardware circuits:\n",
    "Frequency dividers and counters are similar under many aspects to the extent that you can imagine a frequency divider as a counter and a threshold. When the desired number of input positive edges are counted, a positive edged is generated as output. Usually, frequency dividers are designed as a cascade of data flip flops (D-type FF).\n",
    "\n",
    "![D-type flip flop used as frequency halver](https://www.electronics-tutorials.ws/wp-content/uploads/2018/05/counter-cou1.gif)\n",
    "\n",
    "A counter can be obtained in the same way by connecting the output $Q$ of each FF to the desired circuit. Check [this](https://www.falstad.com/circuit/circuitjs.html?ctz=CQAgzCAMB0l3BWEAmM0AsB2SCCcyBGANiMwUjCXJCshoFMBaAggKAISJAA5uVNkIApHT9BBGu05CEg5AKFE+88ZIDuMuQoLpRKqKw06923eBEGjZsBY6CboyIaFgu+gq5S9LLt97tefE4cbsRiKGBaqsHSyNx0+si4btoGIeBm+pRRQpLp6JDKCujIJtFSXFg56N7uPshw4Q0J3k4azYEoYXFBzshEZSgDnW1DerXxI86RRfZxUxoznWCZrdP44WAbPT5bct4Fymsa6LHFsccgp358VQtdKXKF4aMNsyjPDvWfFoRcX69JokFPpXiDwfYLGDIeM6ADppkFGBPKDpiikZ54YtMRYVqIsVdnvoCgkFKMSeEKQSqRZDuZHM47sThqiTizisNqZzaUioc5jPShNZPK8fnpPiL+cK3BKuKK+MjHuBJe1eYNFfUMf9MSrldrKo0NeTDZ50JzdWb8abuQyTobaSa5Wj-ridU6AEo8I4K-Z8CTieAoaBIZDBqBQYPOWoKIFkqOkwSTAlJizeZNw1Nw3VJzwCo2sT05-72EXhgo0cN0GAIfno8Qo0rfBMfBKNV7suTDAiYJ2LeZZeYBUZ7TYbAjzclnQTXIR8jSyZsLnhV1gAWV8KEbQMbckj646HSBjV3Nf3XZ7y6EF5Pa-Ag9kl4CN-XI-HfEmb5QQdPV2kwlEH6-N+t5LpMYEJMBbJWlwsgKrqsF6jQ8wEku+ioZc6F8AgKJrOk2FKggD51DW879goCEoWRgj4S8zgINwgz0aI0ijBRFg0fC65MTQXCTLEwHoAQuAgEQkReiJNTiRI3B0QxPEic8LHTPegiieID7DmO8xEI0n6jDpdCfgZG76bpnhqSZjJ-hYxn-j4tk2bpDT2U5dAWeOK6kXQkxEGEkz6X5blhHZAVcHZ7lzgpWFcBZSkaLFMViZcHhuI2FnII2+liRlojpW2fTHo0xkdKZrZubpcmlUIcnuZVfTnjFukXlV3aNYZSgue1fDuR1TgAPYgJg3WOFcwjURG8CQLgPacMgSCGawA0dcMdCCZA40wJN01ELN81CItImYBJZZjRWm3wNtu3hmwS0xSNa0bbAF0zUQc3XQdO3Hatp3zU9cCXa9e03cdK2jetZ1-VNL1vQtS0QKDD0Q1t0NAx9qn3T9E3PTtgPvUAA) interactive simulation to better understand how it works.\n",
    "\n",
    "More info can be found [here](https://www.electronics-tutorials.ws/counter/count_1.html). This website is also the source of the image used."
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