Got a time-critical application (a photo flash radio trigger). The shutter is open for 16.7mS max. it takes about 2mS for the flash to completely fire. I'd also like to have a confirmation that the flash fire command was received. Instead of having a dedicated transmitter and receiver, I'd like to have units capable of doing both simultaneously.

I'm using Linx SC-PA modules with a 33,600bps max data rate and 3mS typical, 5mS max RX->TX transition time. I know I can eliminate that delay by setting to TX mode at power-on. I'm using a PIC with a hardware UART (currently a 16F876A, but any 28pin will do).

I was thinking of sending one-character commands to minimize the data transfer time.

Does anyone know what sort of delay I might expect between the time I query the serial port and when the data is available? Or what PIC, OSC speed and Baud rate I should use to minimize the time delay?

Also, is there a way to determine when a byte has been received by the UART so that it's not sitting waiting on data or a timeout? I saw something about RCIF in the datasheet. Is it possible to read this and do the HSERIN command if set?

Thank you,

Bryan A. Thompson
[email protected]