Trying to understand serial tx commands

charleyshf · 2009-10-10 01:22

Hello,

I am fairly new to the prop and I have been totally lost with something I have been working on lately.

I have a motor controller (Polu qik2s9v1) which is·asynchronous logic-level, non-inverted serial input at 38400, 8 data bits, one stop bit.

I've been trying to just send it a·command in decimal 141, 127 I am also using the·FullDuplexSerial.spin:

My code:

CON
· _CLKMODE = XTAL1 + PLL16X
· _XINFREQ = 5_000_000

OBJ
··· MOTORS : "FullDuplexSerial.spin"

PUB HEREWE_GO

···· ·MOTORS.START(3, 2, 2, 38400)
····· waitcnt(clkfreq/1_000· + cnt)
····· MOTORS.tx(string("141, 127"))

repeat

I have tried all sort of different things with this and I must be entirely lost on this, can some please help me with this?

Thank You
·

QuattroRS4 · 2009-10-10 01:31

.. I don't know the controller but to send decimal value
should it not be

Motors.dec(127)

Just a thought !

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'Necessity is the mother of invention'

'Those who can, do.Those who can’t, teach.'
'Convince a man against his will, he's of the same opinion still.'

·

charleyshf · 2009-10-10 01:37

QuattroRS4 said...
.. I don't know the controller but to send decimal value
should it not be

Motors.dec(127)

Just a thought !

Hi, thank you for responding,

That's one of the commands I have tried with this setup, I know the controller has tested good, but this motor controller also has an error led that lights up if·there is issue with the data sent, and it lights up no matter what I try to send to it.

This is the pdf on the motor controller
http://www.pololu.com/docs/pdf/0J25/qik_2s9v1.pdf

from the pdf it stats of youi send dec 141,127 to the controller it makes one of the 2 motors go full speed forward....

Thanks again
··

SamMishal · 2009-10-10 01:54

Charley,
I can see a few·problems with your code. Try this new code and see if it works for you.

CON
  _CLKMODE = XTAL1 + PLL16X
  _XINFREQ = 5_000_000
 
 Rx_Pin = 3  'Check this is correct receive pin into the propeller from the polou
 Tx_Pin = 2  'check this iscorrect  transmit pin from the propeller to the Pololu
 
OBJ
    MOTORS : "FullDuplexSerial.spin" 
 
PUB HEREWE_GO
 
   MOTORS.START(RX_Pin,TX_Pin, 0, 38400)  'notice the mode is 0 not 2 as you had it...but check this I might be wrong
   waitcnt(clkfreq/2  + cnt)              'wait 1/2 sec not 1ms which I think is two short to give the FDS time to start up
   MOTORS.tx(141)                         'notice you must transmit the bytes not the text and one at a time
   MOTORS.tx(127)
   repeat

Sam
·

QuattroRS4 · 2009-10-10 01:54

PDF says -

(the circular pin right next to the “A” silkscreen label). This fixes the qik’s baud rate at 38,400 bps, and the qik skips the automatic baud detection phase that normally occurs on start-up.
Has this been done ? If not it says dec(170) has to be sent to take it out of autobaud mode.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
'Necessity is the mother of invention'

'Those who can, do.Those who can’t, teach.'
'Convince a man against his will, he's of the same opinion still.'

·

charleyshf · 2009-10-10 02:01

QuattroRS4 said...
PDF says -

(the circular pin right next to the “A” silkscreen label). This fixes the qik’s baud rate at 38,400 bps, and the qik skips the automatic baud detection phase that normally occurs on start-up.
Has this been done ? If not it says dec(170) has to be sent to take it out of autobaud mode.

Yes, currently I have the jumper on for 38400 baud..

SamMishal · 2009-10-10 02:04

Charley

Even if you want to transmit text not bytes then

····· MOTORS.tx(string("141, 127"))

does not work......it should be

···· MOTORS.Str(string("141, 127"))

But the Pololu expects the command and value to be ONE BYTE binary ie 141 is sent as a byte
of the value 141 = $8D· not as the charachters 1 then 4 then 1 which would be THREE bytes of the
values $31 $34 $31

Sam

QuattroRS4 · 2009-10-10 02:06

@SamMishal
As Charley specified decimal should it not be -

MOTORS.dec(141)
MOTORS.dec(127)

in your example ? I am not familiar with the controller - just reading the data sheet now!

Rgds,
John

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
'Necessity is the mother of invention'

'Those who can, do.Those who can’t, teach.'
'Convince a man against his will, he's of the same opinion still.'

·

SamMishal · 2009-10-10 02:13

QuattroRS4 said...
@SamMishal
As Charley specified decimal should it not be -

MOTORS.dec(141)
MOTORS.dec(127)

in your example ? I am not familiar with the controller - just reading the data sheet now!

Rgds,
John

Hi John,

NO....the Motors.Dec(141) will take the byte 141 and convert it to a text of character 1 then 4 then 1
which are the bytes $31 then $34 then $31 just as if you have done Motors.Str(string("141"))

The Motors.Tx(141) transmists a BYTE whose value is 141 JUST ONE BYTE with value $8D.

This is what is needed since this is what the Pololu expects 2 bytes the first being the command
and the second being the value of the command
ie $8D then $7F.......just two bytes.

The method Motors.Dec or Motors.Str· will NOT work since the first will convert the byte to its TEXT
equivalent which happens to be 3 characters (bytes) and the the second does the same but you did the
conversion yourself to text.

Sam
·

charleyshf · 2009-10-10 02:13

Thank you so much!!! That was it, I would have to guess that between needing more of a delay and the fact that I had the wrong mode set ?

Thank you again!!

SamMishal said...
Charley,

I can see a few·problems with your code. Try this new code and see if it works for you.

CON
  _CLKMODE = XTAL1 + PLL16X
  _XINFREQ = 5_000_000
 
 Rx_Pin = 3  'Check this is correct receive pin into the propeller from the polou
 Tx_Pin = 2  'check this iscorrect  transmit pin from the propeller to the Pololu
 
OBJ
    MOTORS : "FullDuplexSerial.spin" 
 
PUB HEREWE_GO
 
   MOTORS.START(RX_Pin,TX_Pin, 0, 38400)  'notice the mode is 0 not 2 as you had it...but check this I might be wrong
   waitcnt(clkfreq/2  + cnt)              'wait 1/2 sec not 1ms which I think is two short to give the FDS time to start up
   MOTORS.tx(141)                         'notice you must transmit the bytes not the text and one at a time
   MOTORS.tx(127)
   repeat

Sam

Cluso99 · 2009-10-10 02:14

You also had a comma in your string

to send this
motor.tx(",")

You may also need to send a carriage return (CR) and possibly a Line Feed (LF) at the end of the string. To do this
motor.tx(13) 'cr
motor.tx(10) 'lf

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QuattroRS4 · 2009-10-10 02:19

SamMishal said...
But the Pololu expects the command and value to be ONE BYTE binary ie 141 is sent as a byte
of the value 141 = $8D not as the charachters 1 then 4 then 1 which would be THREE bytes of the
values $31 $34 $31

Duly noted ..

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
'Necessity is the mother of invention'

'Those who can, do.Those who can’t, teach.'
'Convince a man against his will, he's of the same opinion still.'

·

Trying to understand serial tx commands

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