USB to Serial Support Requested

We have an application (a microprocessor boot loader) that responds to the PC with a single byte. This is microprocessor dependant and cannot be changed. All of the USB to RS232 adapters that we have tried buffer the incoming data from the micro being loaded with a minimum of 16 bytes. This occurs even when we turn off the “Use FIFO Buffers” in the driver. These adapters work, but due to the delay in sending the microprocessor responses (micro must send 16 responses before they are transmitted to the PC by the adapter) the process that takes less than a minute with an onboard serial port takes several minutes with the adapters. We are looking for a USB to RS232 adapter that will transmit each received byte immediately to the PC as it is received, instead of buffering or delaying it.


Most likely it wouldn’t work with any of our Edgeports, even the newer models that have less buffering.

It doesn’t surprise me that you’re having these problems with USB based serial ports. This type of application (needing timely read/write operations) is best done with onboard serial ports, if possible. You have the ability through Windows to change the FIFO thresholds to 1 byte, etc. Even these (16550 UARTS) will typically have some buffering (16 bytes, etc.) but not nearly as much as a typical USB based serial solution.

Thanks for the reply.