Today, I responded to a PPMScope communications problem e-mail, similar to several others I've responded to in the past. I wanted to share the e-mail at large in hopes that it would help others with similar problems and give me something to refer people to in the future. The following is a description of the problem: Dear sir, We have constructed the circuit on a PCB for PPMscope but we are unable to connect to our PC. The red circle seen on the left of PPMscope screen is always red. We are using a USB to serial converter (FT232RL) to connect to our laptop. Please help us. Sincerely, User And my response: Dear User, I'm going to start with the FT232RL. If you can confirm that the Windows driver is installed, that would be great. If the Windows driver did not install, you can install it manually using this link (http://www.ftdichip.com/Drivers/VCP.htm). If the driver is installed and the device was not recognized, you should check the connections to the FT232RL. I'd start by making sure power is applied to the chip (i.e. 5 volts should be applied to pins 4 and 20, and 0 volts applied to pins 25, 7, 18, 21, and 26). Then I'd check if pin 16 is connected to D- (pin 2 on the USB connector) and pin 15 is connected to D+ (pin 3 on the USB connector). The schematic at http://jonw0224.tripod.com/PPMHelp/USBToSerial.pdf is a good reference. If the driver is installed and the device was recognized, you probably have a good FT232RL. Here is a screenshot of a good FT232RL from device ma...