Do Until I get some new value

SteveWoodrough · 2008-03-02 04:57

What is a good technique to accept a value through the serial port, take some action, and continue with that action until I get some new value through the serial port?

Here's my scenario:
Each mouse click in a seprate program sends a value to the BS2

Without the DO Until x<>Y (or Do While x=Y) the I only get one program loop.· With the Do statements, the program "latches" onto the first command and never stops.

Other than a degree in computer science, what am I missing?

THANKS

DO
··· 'accept decimal value in through serial port 16 at 2400,N,8,1
··· SERIN 16, 16780, [noparse][[/noparse]DEC y]
·············· x = y
·· DO UNTIL x <> y
········· IF x = 1 THEN
········· GOSUB Straight
········· ELSEIF x = 2 THEN
········· GOSUB TurnRight
········· ELSEIF x = 3 THEN
········· GOSUB BackUp
········· ELSEIF x = 4 THEN
········· GOSUB TurnLeft
········· ELSE
········· GOSUB Halt
········· ENDIF
········· GOSUB ApplyPulse
·· LOOP
····
LOOP

Unsoundcode · 2008-03-02 05:27

Hi Steve, if you use the time out function of SERIN there is probably no need for the second DO...LOOP. If you set the time out < 30mS it should still refresh the servos ok

DO

SERIN RX,baud,30,Time_out,[noparse][[/noparse]DEC y]

conditional logic

LOOP

Jeff T.

Bruce Bates · 2008-03-02 06:06

Steve -

As an alternative to Jeff's method (and with some added coding), here is another method you can try. Currently you have the following in your program:

DO
'accept decimal value in through serial port 16 at 2400,N,8,1
··· SERIN 16, 16780, [noparse][[/noparse]DEC y]
··· X = Y
· DO UNTIL X <> Y
··· ...
· LOOP
LOOP

Have the other program send a leading character, such as "!". Then have the SERIN and the additional code look like this:

DO····················· 'Infinite loop

'accept decimal value in through serial port 16 at 2400,N,8,1
··· SERIN 16, 16780, [noparse][[/noparse]WAIT ("!"), DEC y]
··· X = Y·············· 'Save last Y

SELECT X············ 'Field value

·CASE = 1··········· 'Check value
·GOSUB Straight

·CASE = 2··········· 'Check value
·GOSUB TurnRight

·CASE = 3··········· 'Check value
·GOSUB BackUp

·CASE = 4··········· 'Check value
·GOSUB TurnLeft

·CASE ELSE
·GOSUB Halt

·ENDSELECT

'Select termination Point

LOOP

- - - - -

Just make sure at the top of your program you have included this:

' {PBASIC 2.5}

- - - - -

I find it quite a bit "cleaner" with SELECT...CASE, but do what makes you feel comfortable.

Regards,

Bruce Bates

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Programming can't be all that difficult, it's nothing but 1's and 0's

Post Edited (Bruce Bates) : 3/2/2008 6:22:08 AM GMT

SteveWoodrough · 2008-03-02 22:28

Bruce,
Thank You verymuch for your response, but I'm not getting it. I tried it but nothing works.
My understanding is that the "WAIT" for a ! instruction will cause the stamp program to hold at that line until the stamp gets a ! character. If I only send a ! with each mouse click, won't the program hang?

I might be asking the stamp to do the impossible...I want to send the stamp a value of 1, 2, 3, 4 or 5 by clicking the mouse in a VB program.
I want the stamp to take the value sent to it, and execute the corresponding subroutine, and to continue with that executing that subroutine until some other value is sent. As I "talk" this out I need the stamp routine to periodically go back and check if any new data has come in the serial line. Two questions come up in my mind:

When I'm not clicking the mouse button is a 0 or NULL value being transmitted to the stamp?
If data is sent to the stamp when it's not "looking" will the data be lost?

Thanks again for everyone's input!

Below is the code:

VB Code:
Private Sub DataSendButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles DataSendButton.Click
Dim send As Integer = Val(TextDataToStamp.Text)
If _port.IsOpen Then
_port.WriteLine("!" & vbLf & send)
End If
End Sub

BSCode

'

[noparse][[/noparse] Title ]

'{$STAMP BS2}
'{$PBASIC 2.5}
'

[noparse][[/noparse] I/O Definitions ]

LeftServo PIN 13 ' Left Servo
RightServo PIN 12 ' Right Servo

'

[noparse][[/noparse] Variables]

x VAR Word
y VAR Word
PulseLeft VAR Word
PulseRight VAR Word
'

[noparse][[/noparse] Constants ]

pulse CON 15
'

[noparse][[/noparse] Initialization ]

'

[noparse][[/noparse] Main Routine ]

DO 'Infinite loop

'accept decimal value in through serial port 16 at 2400,N,8,1
SERIN 16, 16780, [noparse][[/noparse]WAIT ("!"), DEC y]

X = Y 'Save last Y

SELECT X 'Field value

CASE = 1 'Check value
GOSUB Straight

CASE = 2 'Check value
GOSUB TurnRight

CASE = 3 'Check value
GOSUB BackUp

CASE = 4 'Check value
GOSUB TurnLeft

CASE ELSE
GOSUB Halt

ENDSELECT
'Select termination Point
GOSUB ApplyPulse
LOOP

'+++++++++++SubRoutines+++++++++++++++

timeout:
PAUSE 30
RETURN

ApplyPulse:

PULSOUT LeftServo,pulseLeft
PULSOUT RightServo,pulseRight
PAUSE pulse ' Constant defined above
RETURN

Straight:
pulseLeft = 850
pulseRight = 650
RETURN

TurnRight:
pulseLeft = 850
pulseRight = 850
RETURN

TurnLeft:
pulseLeft = 650
pulseRight = 650
RETURN

BackUp:
pulseLeft = 650
pulseRight = 850
RETURN

Halt:
pulseLeft = 750
pulseRight = 750
RETURN

Tracy Allen · 2008-03-02 22:52

I think that the pause that you have in the applypulse subroutine should be moved up into the SERIN command.

DO'Infinite loop
X = Y 'Save last Y
'accept decimal value in through serial port 16 at 2400,N,8,1   <------- with timeout of length "pulse" milliseconds
SERIN 16, 16780, pulse, continue, [noparse][[/noparse]DEC y]

IF X<>Y THEN EXIT  ' other code

continue:

SELECT X 'Field value

CASE = 1 'Check value
GOSUB Straight

CASE = 2 'Check value
GOSUB TurnRight

CASE = 3 'Check value
GOSUB BackUp

CASE = 4 'Check value
GOSUB TurnLeft

CASE ELSE
GOSUB Halt

ENDSELECT
'Select termination Point
GOSUB ApplyPulse
LOOP
'  other code on EXIT


ApplyPulse:
PULSOUT LeftServo,pulseLeft
PULSOUT RightServo,pulseRight
' leave out the PAUSE pulse here.   It is rolled into the timeout for SERIN   <---------
RETURN

There is a chance the SERIN will miss an input change or that it will read it incorrectly, so the mouse click might have to try again. It is a workaround. The Stamp does not have a serial buffer to store up incoming asynchronous data. It will only receive while it is sitting at and executing the SERIN command, and the SERIN timeout becomes part of the 20 or 30 millisecond loop that refreshes the servos.

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Tracy Allen
www.emesystems.com

Do Until I get some new value

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