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4030 :: How to map object to memory address

• markprocess (orginal) [2018-07-09T10:51:42+02:00] view original

  How do I map an object like

  type

  Usart = object

  cr:int

  to an address like 0x40028000

  Thanks, Mark

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• DeletedUser (orginal) [2018-07-09T12:16:49+02:00] view original

  The addr <https://nim-lang.org/docs/system.html#addr>_ proc returns a ptr T which can be cast into int.

  type
    Usart = object
      cr: int
  
  var x: Usart
  echo cast[int](addr x)
  Run

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• mratsim (orginal) [2018-07-09T12:22:30+02:00] view original

  echo cast[ByteAddress](addr x) is more idiomatic (ByteAddress is an alias to int)

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• Araq (orginal) [2018-07-09T12:26:17+02:00] view original

  That's not how I understood the question. Here is my solution:

  type
    Usart = object
      cr: int
  
  template a(): ptr Usart = cast[ptr Usart](0x40028000)[]
  
  a().cr = 1234
  Run

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• markprocess (orginal) [2018-07-09T12:34:10+02:00] view original

  There is a bank of usart registers at that address and I want to read/write them individually. (I only listed one register - cr - I will need to add more.) i will test this.Thanks!

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• markprocess (orginal) [2018-07-09T14:16:02+02:00] view original

  I get a compiler error - ptr Usart vs Usart - so I changed the return type to Usart instaed of ptr Usart and it compiled. However the c code produced looks like this:

  (*(*((tyObject_UsartcolonObjectType__XTl78bMn519bCizK6Y69cOpQ**) 1073905664))).thr = ((NI) (((NU8)(c))));
  Run

  If I remove one level of indirection in the c code, it works as expected. Mark.

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