Hello,

I am having a difficult problem with the D2XX driver for ARM4 Pocket PC/WinCE devices. The code example provided for the pocketPC on your website is always failing on FT_Read calls. I have my FTDI device connected to my USB host adapter and the FTDI device is recognized and the driver is successfully installed. I am able to list the FTDI devices, open, and set parameters. But every time I try to Read I get an error.

According to the documentation a FT_Read operation should return FT_OK in the event of data received or a timeout. Instead, I am getting a return value of FT_IO_ERROR (4) whenever I try to read.

I have confirmed that the same code works properly on my X86 Windows PC. On the PC I get a return value of FT_OK from the FT_Read function. This rules out the possibility of my FTDI device being the problem.

Keep in mind that this is the sample located on your website at this link:

http://www.ftdichip.com/Projects/CodeExamples/VB.htm

Is there a problem with the driver? Is the demo app on your website incorrect in some way? Without the ability to do a simple Read() I cannot successfully develop applications.

Here is a snippet that represents the relavent code in your demo app:


Dim dwListDescFlags As Integer = FT_LIST_ALL
Dim dwOpenFlag As Integer = dwListDescFlags And Not FT_LIST_ALL
Dim FTstat As FT_STATUS
Dim handle As Integer

Try

FTstat = FT_Open(0, handle)
If FTstat <> D2XX_mod.FT_STATUS.FT_OK Then
MsgBox("Unable to open port (1)")
Exit Sub
End If

FT_SetBaudRate(handle, 9600)
FT_Purge(handle, D2XX_mod.FT_PURGE_.FT_PURGE_RX Or D2XX_mod.FT_PURGE_.FT_PURGE_TX)
FT_SetTimeouts(handle, 3000, 3000)

Dim cBuf(1) As Byte
Dim dwRet As Long

Try
Dim RxBytes As Integer
Dim TxBytes As Integer
Dim EventDWord As Integer

'************************************************* ************************************************** *************
'INFAMOUS READ CALLED HERE.............................................. ............................................
'************************************************* ************************************************** *************
FTstat = FT_Read(handle, cBuf, 1, dwRet)

If FTstat <> FT_STATUS.FT_OK Then
'************************************************* ************************************************** *************
'ALWAYS HITS THIS BREAKPOINT. FT_Read ALWAYS RETURNING 4!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
'************************************************* ************************************************** *************
MsgBox("Fail read...")
Else
If dwRet = 1 Then
MsgBox("Success read")
Else
MsgBox("Success read. timeout")
End If
End If

Catch ex As Exception
MsgBox("Error readin...")
End Try
Catch ex As Exception
MsgBox(ex.Message)
End Try

Please help!

Hello,

Since you are using the FT232BM chip there is a suggestion that could help. I suggest that you put 47pF capacitors on the D- and D+ lines to ground. This will improve the termination of the device.

Also I am not sure what type of USB connector that you have but if there is a USB connector shield pin on it you will want to leave this pin unconnected and not tied to ground.

Regards

James Leary
Support Engineer

FTDI Ltd
373 Scotland Street
Glasgow
Scotland
UK
G5 8QB