I have a vb6 app that communicates with a motorola hc11 device via rs232. I have been using the mscomm control to talk to the serial port and it works okay to recieve text data from the device, but one of the functions I must have is to send new firmware to the hc11. The data is sent in ascii format and the device is using Xon/Xoff flow control. I can't seem to access the flow control with mscomm, so I can't respond quick enough to Xoff events to keep from over flowing the devices buffer. The only way I can get it to work is to send one character at a time and then wait a certain amount of time for a recieve event. This is dreadfully slow and unreliable. I am now trying to use api functions but am having trouble with writefile(). Anybody have any ideas? I can post source code if it helps.