connecting avr atmega32 to shift register using USART?

Question

I want to connect ATMEGA32 microcontroller to a shift register using USART via TXD pin, the shift register then performs serial to parallel conversion on the received data. but as you know, the shift register needs clocking , this clocking is fed via the microcontroller at baud rate frequency via XCK pin (here the USART acts as master synchronous clock generator). My problem is that i don't know how to get these clock signal out of XCK, so how to do that???

thanks

Answer 1

RS-232 is self-clocking (fix baud rate) - it typically uses x16 clock supplied to a UART which syncs to the incoming data start bit edge. Rather than use a bare shift register you would probably be better off just using a simple UART chip as your serial to parallel converter - it would save a lot of effort.

Answer 2

I don't think using the UART for the shift register would be a good idea. It would be better to use the SPI mode of communication as it also provide the clock you require for the shift register. But if you want to use UART then you would have to provide a separate clk in sync with the baud rate you've selected for the UART mode which I think would be very hard and inaccurate.