On Thu, Apr 01, 2010 at 01:43:51PM -0400, Andrew Kohlsmith (mailing lists account) wrote: > On Thursday 01 April 2010 01:36:52 pm Fabio Giovagnini wrote: > > I' have connected my SCIF1 port (of sh2a 7203) to a MAX485, and the > > TXEn/!RxEn to an I/O port. > > I had the idea to write a driver for proc FS to manage the TxEn/!RxEn line > > and using the ttySCx driver to send and receive data at 38400. > > But I need to wait the end of the last byte trasmission before to set low > > the TxEn/!RxEn line. > > Now I'm doing it with a dilay time; but I was looking for a more elegent > > solution > > There are a couple of solutions that are more elegant. > > First is to have a "transmitter shift register empty" interrupt deassert the > line, but that's not the most elegant, if you hardware has support to > automatically control the RS485 transmitter enable pin. > > Some UARTs have the ability to do this (ColdFire does for sure, I've never > used SH2A) but check your UART documentation for the ability to automatically > control a transmit enable pin.
Yeah I have only ever done it using a UART that can automatically control the direction based on the transmit FIFO containing data or not (with a programable delay before switching of the transmitter of course). I would hate to try and do it from software with an interrupt. Yuck. -- Len Sorensen _______________________________________________ uClinux-dev mailing list uClinux-dev@uclinux.org http://mailman.uclinux.org/mailman/listinfo/uclinux-dev This message was resent by uclinux-dev@uclinux.org To unsubscribe see: http://mailman.uclinux.org/mailman/options/uclinux-dev
