Serial COM Ports in Excel VBA

Copper Contributor

Hello all,


I've uploaded a new set of VBA functions for anyone still interested in using Serial COM Ports with Excel. 


GitHub - Serialcomms/Serial-Ports-in-VBA-new-for-2022: Using Serial COM Ports in Visual Basic for Ap...


Let us know if they work for you thanks. 



14 Replies
Thank you for these VBA functions. I have been looking for similar solution for a long time. For the time being it is working without any problems.
great functions!
all by win32 api really complex.
I used to work with Micosoft comm Control6.0 many years ago.


No options : THANK YOU VERY MUCH !!!!!!!! I spent hours for making Open/Input/Get ... working with nothing else than a void answer. Now it works extremely well. No doubts : it's a high contribution to the  professional Excel VB developers community. Warm congrats again

@serialcomms Hello,

One additional question: I need to identify a device connected to a given port. How to get some device info (like its name, type or anything significant) ?


Thanks in advance for your feedback.


Maybe you should try this:


'Loops through all the USB controllers and devices (sticks, hubs, etc.) and retrieves information.
'The code uses a WMI script in order to access the Win32_USBControllerDevice class.

'Written By: Christos Samaras
'Date: 13/01/2014
'E-mail: email address removed for privacy reasons

First of all, thanks for the VBA code! I'm one of those infrequent VAB user and use it occasionally. I do have a problem using the code to write/read from an instrument connected to a PC via serial port. The problem is that the analytical instrument does not start sampling when I send "SS" using TRANSMIT_COM_PORT with VBA in Access to the COM port, whereas it does if I use Putty or a Windows form application previously written with I don't know why. It seems to me the transmission mechanism is different. Any advice will be much appreciated!



Hello and thanks for your interest in SerialComms VBA.


You may have a timing problem between VBA and your instrument. 


Modern PC is simply far too fast for relatively slow serial ports and attached devices.


Try adding a delay between starting the COM port and sending the Start Sampling command. 


Add a second delay between sending the command and waiting for a response.


There's an example function at the end of the listing below which shows how to do that. 


Serial-Ports-in-VBA-new-for-2022/SERIAL_PORT_VBA.bas at main · Serialcomms/Serial-Ports-in-VBA-new-f...






Thanks for your reply. I figured it out - it's as simple as sending a carriage return at the end of the command string!
It is great that you have provided these functions. However I am having a similar issue talking to an Arduino. Neither the example() or the, ..transmit, ..receive in a subroutine work. However if I run the functions in the immediate window, then it does work. If I insert breakpoints on my subroutine at each function then again it does work. However if I add delays using either sleep() or the waitcomport() function it does not work. If I step through the breakpoints too fast in my subroutine I can get it to not work, so it is clearly a time related issues, but I cannot see why the delays within example() or the delay in my subroutine do not work for me.
Regards Andrew Mellon
I have solved this: I needed to add a delay between the open port and transmit in my own subroutine. This despite the fact that the transmit reported sending the data sucessfully. I then went back to the example and invcreased the delay before If Port_Started(Port_Number) Then to 2000 and it worked.
Thanks again for the code.
Regards Andrew M





At least one Arduino model (Uno R3) will intentionally reboot when a serial connection is made to it. This may explain the need for a delay after opening the port as you have discovered. 


The following Github repository contains a modified version which allows an Arduino serial connection to be made without rebooting it. 


Serialcomms/Serial-Ports-in-VBA-Arduino-2023: Arduino R3 serial version (


There is also a separate function to reboot the Arduino if you need it, and a sample Arduino sketch to send analogue channel values to the serial port. 


Note also that the Uno is relatively slow compared to a modern PC which further increases the need for timing delays. 





@serialcomms  Thankyou for the help it was useful. I should have realised by Arduino was rebooting on connection.  It explains some other things I did not understand happening.  First use of Arduino.  I will certainly look at the Arduino version.  

Thanks Andrew M

@serialcomms hello, I am using excel 2106 and I used your module which is much appreciated! My problem is I can connect to the port with the correct baud rate and all but when I send a command then request to receive what should be displayed I just get a mirror of what I sent.

example sent: (EX)

received :  (EX)

This should return a software and firmware ascii text. I tried using \r\c or one of each at the end of the sent string and I just revive that added text back.

please help and thanks!




Hello - what serial device are you trying to connect to please ?