[Tinyos-devel] Proposed UART Changes

[Trevor Pace]

Hey Eric,

The problem I am seeing right now is that I am developing a module which
should in theory work on any mote that supports UART. However, there exists
no hardware abstraction interface provided by all platforms that would allow
me to disable/enable communication.  It does exist at the lower HPL but that
is implemented per chip.

So for me to shut-off my reception temporary I must wire a chip-specific HPL
Uart module removing the possibility of compatibility with other chip sets.
The Msp430HplUart you mentioned does support enabling/disabling for sure,
unfortunately by the time it gets to the PlatformSerialC abstraction (which
is available to all chipsets with UART) then I lose that ability.

Trevor Pace


On Wed, Jun 17, 2009 at 3:51 PM, Eric Decker <cire831 at gmail.com> wrote:

> 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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