Kinetis Microcontrollers中的主题 Re: How can I do 2 stop bits on a K60 UART2 at 9600 baud rate

How can I do 2 stop bits on a K60 UART2 at 9600 baud rate

batwings — Tue, 10 Feb 2015 18:50:17 GMT

I don't see a way to do 2 stop bits, or on the K60 UARTs. I'm using UART2

I need to connect to a device via rs232 to do modbus communication with the following settings:

The serial communication parameters are

 BPS: 9600 baud

 Parity: None

 Data bits: 8

 Stop bits: 2

 Flow control: None

Any suggestions?

Re: How can I do 2 stop bits on a K60 UART2 at 9600 baud rate

egoodii — Tue, 10 Feb 2015 19:16:37 GMT

Reception of two-stop bits, when the controller is only set for one, isn't a problem of course -- excepting that you won't get any kind of 'fault' if the 2nd stop bit isn't proper. For the TX side, I think you will find that if you work with the transmit-shift-register-empty bit/interrupt for loading the 'next byte' that you will get that extra stop bit on TX, as it takes one bit time for a data byte to make it from the buffer to the TX shift register.

Re: How can I do 2 stop bits on a K60 UART2 at 9600 baud rate

egoodii — Tue, 10 Feb 2015 19:30:52 GMT

Or, a 'more direct' method would be to set the UART for '9 bit' mode (UART2_C1 'M'), and then in UART2_C3 set/confirm-valid-stop#1 'bit 8' as T8/R8.

Re: How can I do 2 stop bits on a K60 UART2 at 9600 baud rate

batwings — Tue, 10 Feb 2015 19:39:04 GMT

Thanks for the quick suggestions. I will give this a try and report back!

Re: How can I do 2 stop bits on a K60 UART2 at 9600 baud rate

mjbcswitzerland — Wed, 11 Feb 2015 00:09:50 GMT

Hi Jason

MODBUS never uses 2 stop bits for its communication (see MODBUS over serial line specification) - it has a fixed 10 bit length for both ASCII and RTC.

If nevertheless required, the method for the K series is also described here: K20 UART with 2 stop bit or parity although can't be used in DMA mode.

The UART driver in the uTasker project will respect true 2 stop bits on Kinetis K-parts if the option TRUE_UART_TX_2_STOPS is enabled and the UART is opened for 2 stop bit mode (on all 6 UARTs). µTasker Kinetis support

If you are developing a MODBUS project, be advised that a complete solution for the Kinetis is available at µTasker MODBUS Extension pack which supports serial master and/or slave on all UARTs in RTU and/or ASCII modes, handles RS485 mode, as well as multiple MODBUS TCP sessions (master and/or slaves) with gateway and routing capability.

Comprehensive user's manual: http://www.utasker.com/docs/MODBUS/uTasker_MODBUS.PDF

and industrially proven in Coldfire (and more recently Kinetis) projects since 2009. It was also embedded in support equipment controlling the Claw used by U2 on their 306° World Tour: µTasker Project Page

Regards

Mark

Kinetis: http://www.utasker.com/kinetis.html

K60: µTasker Kinetis TWR-K60N512 support / µTasker Kinetis TWR-K60D100M support / µTasker Kinetis TWR-K60F120M support

For the complete "out-of-the-box" Kinetis experience and faster time to market