• PicŪ Basic


  • PIC18F or Amicus18 Hbusin/Hbusout BASIC code Replacement

    by
    Les
    Published on 4th December 2015 14:37
    For those of you who are at a more advanced programming stage, presented here is an include file that will replace the compiler's HBusin, HBusout, HBStart, HBReStart, HBStop, HBusAck and HBusNak, hardware peripheral I2C, commands with their BASIC code equivalents.

    Why would you want this?
    Changing the nature of code is what programmers do best, and being able to alter the underlying code that the compiler normally created in assembler mnemonics, has many possibilities.

    The code below shows the use of the HBusin/HBusout commands, but uses the replacement code routines. As you can see, there are no differences between this code, and the normal use of these commands, except for the addition of the "Hbus.inc" include file at the top of the program.

    Code:
    '
' Demonstration for using the HBusin/HBusout code replacement routines
'
  Include "Amicus18.inc"           ' Configure the compiler to use a PIC18F25K20 at 64MHz. i.e. an Amicus18 board
  Include "Hbus.inc"               ' Load the replacement code for the HBusin, HBusout etc commands.
'
' Interface to a 24LC256 serial eeprom
' And display on the serial terminal the results
'
  Dim bLoop As Byte               ' Loading/retrieving loop
  Dim sMyString As String * 10    ' String to hold response
'
' Write bytes to the I2C bus
'
  HRSOut "Writing\r"              ' Transmit our intention to the serial terminal

  HBStart                         ' Send a Start condition
  HBusOut $A0                     ' Target an eeprom with bus address 0, and send a Write command
  HBusOut 0                       ' Send the High Byte of the address
  HBusOut 0                       ' Send the Low Byte of the address
  For bLoop = "0" To "9"          ' Create a loop containing ASCII 0 to 9
    HRSOut bLoop                  ' Display the value on the serial terminal
    HBusOut bLoop                 ' Write the value of bLoop to the eeprom
  Next                            ' Close the loop
  HBStop                          ' Send a Stop condition
  DelayMS 5                       ' Wait for the data to be entered into eeprom matrix
'
' Receive bytes from the I2C bus
'
  Clear sMyString                 ' Clear the string before we start
  HRSOut "\r\rReading\r"          ' Transmit our intention to the serial terminal

  HBStart                         ' Send a Start condition
  HBusOut $A0                     ' Target an eeprom with bus address 0, and send a Write command 
  HBusOut 0                       ' Send the High Byte of the address
  HBusOut 0                       ' Send the Low Byte of the address
  HBReStart                       ' Send a Restart condition
  HBusOut $A1                     ' Target an eeprom with bus address 0, and send a Read command
  For bLoop = 0 To 9              ' Create a loop
    sMyString[bLoop] = HBusIn     ' Load the String with bytes received
    If bLoop = 9 Then             ' Are we at the last byte?
      HBStop                      ' Yes. So send a Stop condition
    Else                          ' Otherwise...
      HBusAck                     ' Send an Ack condition
    EndIf
  Next                            ' Close the loop
  HRSOut sMyString, 13            ' Display the received string on the serial terminal
  Stop
    Changing the pins used for the SDA and SCL lines uses the same mechanism of Declares, and these can be found within the "Hbus.inc" file. However, because the Hbusin and Hbusout commands use the microcontroller's dedicated MSSP peripheral, their pins are fixed to PORTC.3 and PORTC.4.

    The include file, as well as the above demonstration code can be downloaded from here. HBus Replacement Code.zip

    A suitable circuit for the above program is shown below:




    The same circuit is shown below built on the Amicus18 Companion shield:




    A top down view of the same layout is shown here:





    The sketchup 7 drawing of the above layout can be downloaded from here:     Sketchup Companion Shield with I2C eeprom.zip

    Les Johnson