Forum Discussion
Serial COM Ports in Excel VBA
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 ...
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 VB.net. 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.
Regards,
SerialComms
- 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 ..open, ..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 MHello,
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 (github.com)
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.
Regards,
Serialcomms.
- Thanks for your reply. I figured it out - it's as simple as sending a carriage return at the end of the command string!
