[Tinyos-devel] Proposed UART Changes

[Eric Decker]

Hi Trevor,
I watch this list also but do not speak for the core group.

That said.  What you've proposed below closely mirrors similar interfaces
that have been implemented for the MSP430 based platforms.

Take a look at tos/chips/msp430/usart/HplMsp430Usart1P.nc

there is enableTxInt and enableRxInt and friends.

eric


On Wed, Jun 17, 2009 at 9:10 AM, Trevor Pace <trevorpace at gmail.com> wrote:

> I am currently working as a research assistant for Dalhousie University and
> I have been given the task of interfacing a Glucose Meter with a Crossbow
> Iris mote. I have written private modules that request and process data
> using the UART0 module on the Iris Atmega128 processor. However, I ran into
> a few issues with UART and TinyOS.
>
> FIRST:
>
> The Glucose Meter communicates at 9600 baud however the default baud rate
> for the iris mote is defined in /platforms/micaz/hardware.h as such:
>
> enum {
>   PLATFORM_BAUDRATE = 57600L
> };
>
> This means that in order for me to use a different baud rate I must change
> that to 9600L, which is not good. My proposed solution to this (that I am
> currently using) is to use pre-compiler defines:
>
> #ifndef PLATFORM_BAUDRATE
> #define PLATFORM_BAUDRATE 57600L
> #endif
>
> That allows me to just add to my makefile:
>
> CFLAGS += -DPLATFORM_BAUDRATE=9600
>
> And sure enough it works for that program only, as it should.
>
> SECOND:
>
> The way the glucose meter is setup it is only possible to do Half-duplex
> communication, and whatever I transmit using UartByte.send() will be
> received; throwing the event UartStream.receivedByte(). This means that I
> must disable reception for the UART module (not just interrupts because the
> module will still be buffering the received data). However, there exists no
> command to disable/enable either the receive or transmit modules at the
> PlatformSerialC abstraction (which provides common interfaces to all types
> of motes supporting UART communication).
>
> My solution for this was to write a function to disable reception and then
> send a byte, though this only will work for ATM128 processors:
>
> CLR_BIT(UCSR0B, 4);
> call UartByte.send(byte);
> SET_BIT(UCSR0B, 4);
>
> My proposed solution for this is to create a new interface called
> UartControl which provides at least the following commands:
>
> command void disableRx();
> command void enableRx();
> command void disableTx();
> command void enableTx();
>
> They could of course return errors if need be. This interfaces would be
> provided from the HPL abstraction to the PlatformSerialC module which would
> then pass it on. Thus providing the ability to disable/enable reception or
> transmission of the UART module.
>
> I am just wondering whether this is an area you feel that TinyOS should
> move towards. Surely there are other devices which may want to communicate
> using serial communication so these ideas won't apply to just my own
> situation. If you feel that this is something you would like to see I would
> be more than willing to write the code to implement this.
>
> Trevor Pace
>
> _______________________________________________
> Tinyos-devel mailing list
> Tinyos-devel at millennium.berkeley.edu
> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-devel
>
>


-- 
Eric B. Decker
Senior (over 50 :-) Researcher
Autonomous Systems Lab
Jack Baskin School of Engineering
UCSC
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