On Sat, 29 Oct 2016 01:51:19 +0300, upsidedown@downunder.com wrote:>On Fri, 28 Oct 2016 10:17:43 +0200, David Brown ><david.brown@hesbynett.no> wrote: > >>> I believe that the only reasonable thing to do would be to finish sending >>> the character, then wait until CTS is asserted before sending. >>> >> >>Yes, anything else would disrupt the low-level behaviour of the UART, >>which is designed to transfer in units of one character. If the >>transmitter broke off in the middle of the character, a receiver would >>see the start of the character followed by high bits. >> >>I also think it is odd to see something using hardware flow control in >>modern devices. Hardware flow control can be a real pain when you have >>buffers, FIFOs, DMA, etc. Flow control is usually handled at a higher >>protocol level now. Rather than using CTS/RTS, or XON/XOFF, you define >>it at a higher level such as replying to telegrams with NACK's. Or you >>just note that since your UART is running at perhaps 115kbps or less, >>and your microcontrollers are running at 50 MHz or more, you don't need >>any kind of flow control - each side is ready all the time. >> > >The last time I used true RTS/CTS handshaking was with a serial >matrix printer a few decades ago. > >The CTS pin is sometimes used to control the Data Direction pin on an >RS-485 two wire half duplex transceiver. Unfortunately, the garden >variety 14550 family UARTs turn off the CTS pin, when the last >character is moved into the transmit shift register, _not_ when the >last stop bit is actually transmitted from the UART. >Correction: The RTS pin is more often used for data direction control
UART behavior for CTS/RTS - Kinetis bugs?
Started by ●October 27, 2016
Reply by ●October 29, 20162016-10-29
Reply by ●October 29, 20162016-10-29
On Sat, 29 Oct 2016 09:03:47 +0100, Paul <paul@pcserviceselectronics.co.uk> wrote:>In article <4c2f9b2e-570c-475a-8838-ef024e90518b@googlegroups.com>, >drn@nadler.com says... >> >> On Thursday, October 27, 2016 at 4:42:07 PM UTC-4, Don Y wrote: >> > ...A TWX would handle this differently than a modern PC, etc.... >> >> Of course, as a 'modern' PC hasn't had a serial port in a decade ;-) > >Side point actually not true. > >For Laptops/netbooks/Phones/tablets that is true.Five years ago, I was able to buy a laptop with a _real_ UART, not one with on board USB/Serial converter. But I guess this would be impossible these days.
Reply by ●October 30, 20162016-10-30
In article <9q091c9ou458mfg6i85r8n2n4n2bo175ol@4ax.com>, upsidedown@downunder.com says...> > On Sat, 29 Oct 2016 09:03:47 +0100, Paul > <paul@pcserviceselectronics.co.uk> wrote: > > >In article <4c2f9b2e-570c-475a-8838-ef024e90518b@googlegroups.com>, > >drn@nadler.com says... > >> > >> On Thursday, October 27, 2016 at 4:42:07 PM UTC-4, Don Y wrote: > >> > ...A TWX would handle this differently than a modern PC, etc.... > >> > >> Of course, as a 'modern' PC hasn't had a serial port in a decade ;-) > > > >Side point actually not true. > > > >For Laptops/netbooks/Phones/tablets that is true. > > Five years ago, I was able to buy a laptop with a _real_ UART, not one > with on board USB/Serial converter. But I guess this would be > impossible these days.Considering most of the mobile type devices are trending to thin as possible (meaning breakable as possible), these days to have a true serial port on these types of devices and DB9 would require cable adapter or docking station. -- Paul Carpenter | paul@pcserviceselectronics.co.uk <http://www.pcserviceselectronics.co.uk/> PC Services <http://www.pcserviceselectronics.co.uk/pi/> Raspberry Pi Add-ons <http://www.pcserviceselectronics.co.uk/fonts/> Timing Diagram Font <http://www.badweb.org.uk/> For those web sites you hate
