Stop mode uart wakeup

jmramil · ‎2010-01-10

Posted on January 10, 2010 at 11:59

jmramil · ‎2009-10-27

Posted on October 28, 2009 at 06:12

Hi all,

I need to wake-up from the STOP mode when a start bit is received in RX signal in order to receive the byte that is coming (and not lose it!). I think that it could be done through the XTI configuring the RX gpio to dispatch a wake-up event and maintain the uart configured.

As my CLK is 16Mhz and the stop mode needs 2048 clks to resume, the expected time to wake would be 128uS and this could limit the current uart baudrate a lot. (less than 9600bps)

So, how I could get this running with higher baudrates?

tomas23 · ‎2009-12-27

Posted on December 27, 2009 at 20:03

Usual solution is, that the protocol counts with first byte lost. No other way of resuming fast enough.

kaouther · ‎2010-01-10

Posted on January 10, 2010 at 11:59

If you will use the USART RX line to wakeup from stope mode using the first byte received, you may discard the first data because system may not decode correctly the first byte just after wake-up.

Usually the first byte is just a premable data to wake-up properly from stop mode . It is advised to configure the UART wake-Up Event of RX Line on the Falling edge to have the shortest wake-up time to gain 1 bit time in order to have a clean High level on the RX and device ready to receive the next data and the Start bit will be decoded correctly. Hope ot helps.

😉