Reorganize website docs (#1806)

Updates to chisel3 documentation for website:
* guard code examples with mdoc and fix errors encountered along the way
* move some website content here vs splitting the content across two repos
* Bring in the interval-types and loading memories content so that it will be visible from the website
* remove all references to the wiki (deprecated)
* Remove reference to Wiki from the README
* fix tabbing and compile of chisel3-vs-chisel2 section
* Appendix: faqs now guarded and compile
* FAQs: move to resources section

1 files changed, 137 insertions, 0 deletions

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+---
+layout: docs
+title:  "Printing"
+section: "chisel3"
+---
+
+# Printing in Chisel
+
+Chisel provides the `printf` function for debugging purposes. It comes in two flavors:
+
+* [Scala-style](#scala-style)
+* [C-style](#c-style)
+
+### Scala-style
+
+Chisel also supports printf in a style similar to [Scala's String Interpolation](http://docs.scala-lang.org/overviews/core/string-interpolation.html). Chisel provides a custom string interpolator `p` which can be used as follows:
+
+```scala mdoc:invisible
+import chisel3._
+```
+```scala mdoc:compile-only
+val myUInt = 33.U
+printf(p"myUInt = $myUInt") // myUInt = 33
+```
+
+Note that when concatenating `p"..."` strings, you need to start with a `p"..."` string:
+
+```scala mdoc:compile-only
+// Does not interpolate the second string
+val myUInt = 33.U
+printf("my normal string" + p"myUInt = $myUInt")
+```
+
+#### Simple formatting
+
+Other formats are available as follows:
+
+```scala mdoc:compile-only
+val myUInt = 33.U
+// Hexadecimal
+printf(p"myUInt = 0x${Hexadecimal(myUInt)}") // myUInt = 0x21
+// Binary
+printf(p"myUInt = ${Binary(myUInt)}") // myUInt = 100001
+// Character
+printf(p"myUInt = ${Character(myUInt)}") // myUInt = !
+```
+
+We recognize that the format specifiers are verbose, so we are working on a more concise syntax.
+
+#### Aggregate data-types
+
+Chisel provides default custom "pretty-printing" for Vecs and Bundles. The default printing of a Vec is similar to printing a Seq or List in Scala while printing a Bundle is similar to printing a Scala Map.
+
+```scala mdoc:compile-only
+val myVec = VecInit(5.U, 10.U, 13.U)
+printf(p"myVec = $myVec") // myVec = Vec(5, 10, 13)
+
+val myBundle = Wire(new Bundle {
+  val foo = UInt()
+  val bar = UInt()
+})
+myBundle.foo := 3.U
+myBundle.bar := 11.U
+printf(p"myBundle = $myBundle") // myBundle = Bundle(a -> 3, b -> 11)
+```
+
+#### Custom Printing
+
+Chisel also provides the ability to specify _custom_ printing for user-defined Bundles.
+
+```scala mdoc:compile-only
+class Message extends Bundle {
+  val valid = Bool()
+  val addr = UInt(32.W)
+  val length = UInt(4.W)
+  val data = UInt(64.W)
+  override def toPrintable: Printable = {
+    val char = Mux(valid, 'v'.U, '-'.U)
+    p"Message:\n" +
+    p"  valid  : ${Character(char)}\n" +
+    p"  addr   : 0x${Hexadecimal(addr)}\n" +
+    p"  length : $length\n" +
+    p"  data   : 0x${Hexadecimal(data)}\n"
+  }
+}
+
+val myMessage = Wire(new Message)
+myMessage.valid := true.B
+myMessage.addr := "h1234".U
+myMessage.length := 10.U
+myMessage.data := "hdeadbeef".U
+
+printf(p"$myMessage")
+```
+
+Which prints the following:
+
+```
+Message:
+  valid  : v
+  addr   : 0x00001234
+  length : 10
+  data   : 0x00000000deadbeef
+```
+
+Notice the use of `+` between `p` interpolated "strings". The results of `p` interpolation can be concatenated by using the `+` operator. For more information, please see the documentation
+
+### C-Style
+
+Chisel provides `printf` in a similar style to its C namesake. It accepts a double-quoted format string and a variable number of arguments which will then be printed on rising clock edges. Chisel supports the following format specifiers:
+
+| Format Specifier | Meaning |
+| :-----: | :-----: |
+| `%d` | decimal number |
+| `%x` | hexadecimal number |
+| `%b` | binary number |
+| `%c` | 8-bit ASCII character |
+| `%%` | literal percent |
+
+It also supports a small set of escape characters:
+
+| Escape Character | Meaning |
+| :-----: | :-----: |
+| `\n` | newline |
+| `\t` | tab |
+| `\"` | literal double quote |
+| `\'` | literal single quote |
+| `\\` | literal backslash |
+
+Note that single quotes do not require escaping, but are legal to escape.
+
+Thus printf can be used in a way very similar to how it is used in C:
+
+```scala mdoc:compile-only
+val myUInt = 32.U
+printf("myUInt = %d", myUInt) // myUInt = 32
+```