I am using an MSP-EXP430F5529LP. I have written some firmware that communicates with a LabVIEW application running on a PC using the serial to USB communication on the development board. The LabVIEW application requests some data, and the microcontroller responds. Both request and response are about 5 to 6 bytes each. I am running the serial port at 115200 buad 8-N-1. Everything work OK, except there is a nearly 90 ms delay between receiving the request, and receiving the first byte of the response. After the first byte, all the other bytes come in in under 1 ms. I put a scope on the RX and TX lines on the development board, and the firmware is responding in less than 1 ms, so the firmware isn't the issue. The delay was 600ms, but then I realized I can make it a lot shorter be turning off the debugger, which makes sense.
I have a feeling this delay is caused by the USB to serial hardware, or, more like, the USB driver. I have noticed a few thing about the driver that make me think it is a bit flaky (like the com port changing when I unplug and re-plug).
Does anyone know what might be causing this delay?
Does anyone have any idea how I might be able to narrow down what is causing it?