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Serial Port functions in VBA Simple 2022

This is the simplified set of VBA Serial Port functions for use with one pre-defined Com Port only.

Intended for use with serial devices which have a well-defined set of short commands and responses.

No debug or extended transmit & receive functionality is provided.

No other files, licences, payments or registrations are required.

Functions can be used directly in Excel cells as Formulas where appropriate.

Com Ports

  • Functions work with both Hardware and Virtual (software) Com Port types

  • All API functions are 'Synchronous' as some port types do not respond correctly in 'Overlapped' mode

Read Functions

Assume that all data has already been sent by the attached serial device and is ready waiting to be read

  • check_com_port can be used to confirm expected number of characters are waiting before committing read

  • No pre or post read delays for any in-flight data reception to complete are provided.

  • Data will be read in one synchronous API call.

  • Maximum characters per read call = READ_BUFFER_LENGTH

  • check_com_port function can be used again to check for any new or remaining characters.

Write Functions

Writes are synchronous and functions can block until outgoing data is processed or write timer expires

  • Short strings will return quickly as data is buffered for transmission
  • Maximum number of characters sent is limited by write timer value in milliseconds
  • Character limit per send is approximately = ( Baud Rate * WRITE_CONSTANT ) / 10000

Control Functions

Com Port Start, Stop

  • Allow a few MilliSeconds for functions to return and for any attached hardware to stabilise
  • Functions return True or False to indicate success or failure

Data Waiting Check

  • Function returns number of characters waiting to be read
  • Return number can be zero if no data waiting
  • Return value of -1 indicates error, including port not started

Device Ready Check

  • Function returns True if port started and Data Set Ready input signal is active

Function List Table