If you feel that one of your COM ports is malfunctioning you can try testing its read/write ability. This will require inserting a loopback tool into your Serial port.

 

This tool will receive the data and then push it back through the COM port to be received by the computer. 

 

Here is the powershell command to use for this test. Change the COM7 in this example to whatever your COM port is for what you're using. 

 

Copy and paste all the below text into powershell.

 

If you had put the correct COM port to replace the 7 for what is assigned and you get failures it could mean you need to send your unit in for repair.

 

$portName = "COM7"
$baudRates = @(4800, 9600, 14400, 38400, 115200)
$attemptsPerBaud = 10
$testMessage = "LoopbackTest"
$allSuccessful = $true

foreach ($baud in $baudRates) {
    Write-Host "`n--- Testing Baud Rate: $baud ---"

    for ($i = 1; $i -le $attemptsPerBaud; $i++) {
        try {
            $port = New-Object System.IO.Ports.SerialPort $portName, $baud, "None", 8, "One"
            $port.ReadTimeout = 2000
            $port.WriteTimeout = 2000
            $port.Open()

            Write-Host "[$baud] Test ${i}: Sending '$testMessage'"
            $port.WriteLine($testMessage)
            Start-Sleep -Milliseconds 200

            $response = $port.ReadLine()
            Write-Host "[$baud] Test ${i}: Received '$response'"

            if ($response.Trim() -ne $testMessage) {
                Write-Host "[$baud] Test ${i}: Mismatch in loopback data."
                $allSuccessful = $false
            }

            $port.Close()
        } catch {
            Write-Host "[$baud] Test ${i}: Timed out or error: $_"
            if ($port -and $port.IsOpen) { $port.Close() }
            $allSuccessful = $false
        }
    }
}

# Final result
if ($allSuccessful) {
    Write-Host "`n✅ COM port '$portName' is functioning correctly on all tested baud rates."
} else {
    Write-Host "`n❌ COM port '$portName' failed one or more tests. Check loopback or port status."
}