Servo Controller PARALLAX

[Almasri]

Hi,

i want to control 12 servo motors using a PIC16F877A, the only servo controller i found and i bought was the (parallax servo controller), i have connected the servo controller to the PIC board using an RS232 cable, now i have to send signals to the Servo board to get the motors starting:
according to their manual
Each position command is comprised
of a header, three parameters: C, R, and PW, and a command terminator.
The Header: “!SC” is the header. The header signifies to all devices on the same wire that this is a command for a Servo Controller.

if i want to pass it to the PIC i have to USe PUTC() is that correct..??
and how can i pass a command which is readable by the servo controller such as the "!SC" ...???
did anybody ever came across this controller and is it possible to provide me with a simple example

thank you very MUCH

[Ttelmah]

Much easier to use printf, than putc. Putc, passes a single character, or a 'constant' string. Printf, generates formatted output strings.
The parallax 'move' command for example, requires 'channel', 'ramp', and then the position as two bytes. An example of a function to send this might be:

[Almasri]

when i tried it the motor stalled , don't i have to include a termination command as they mentioned in PARALLAX CR $0D

so in pic PCw it should look like

printf("!SC%1c%1c%1c%1c/R",servo_number1,ramp,make8(position,0),make8(position,1), 0x0D);

[Ttelmah]

No.
The problem is that I typed the wrong '\'. I am on a different keyboard to normal, and it has some keys swapped.
\R, is a C standard code for a 'carriage return' (0x0D).
There are a number of such codes.
If the motor stalls then you need to change the ramp rate. This is described in the data sheet.

Best Wishes

[Almasri]

thanks for your fast reply , its still stallin, well another problem , when i connected 2 of them they all moved and stalled looks like it doesn't matter which motor i choose they all move ,, i think this problem is from the (3-conductor cable to stereo (RS232)), i m going to try another cable

[Almasri]

Hi Ttelmah

can you please confirm that my program is right, i am trying to make the motor turn ... from one postion to another ....
this is my first experience with PARALLAX and before checking the rs232 cable i wanted to confirm this with you
thanks alot

[Ttelmah]

Two problems. The first problem is your two position declarations. You need:
int16 position1=1250L;
int16 position=250L; // 250 to 1250 0-180 deg

Notice the 'L', not '1'. You are trying to move the servo to impossible positions. The driver only accepts values from 250 to 1250. 'L' makes sure the compiler knows you are dealing with a 'Long' value, while an extra '1' makes it into an impossibly large value!.
In this case, because the value is directly put into a 'Long', the declaration is not really needed. I had it in my 'tests', because with the 250 in particular, it is worth making absolutely 'sure' that the compiler knows what you want. The lower case 'l', is very difficult on some fonts/screens, to 'tell' from a '1'.
You still show a '/R', not a '\R'. You need the latter.

Best Wishes

[Almasri]

Thanks for the help ,,

i changed the RS232 wire and resolder everything in place, unfortunatly still the same problem

when i try that and connect more motors all of them stall, even when i connect one its stalls,
Given that i am only calling one servo motor, (same code you have corrected for me)
i have tried ramps between 0 and 63, i doubled check the voltage and current on motors and board, nothing changed
motors that i am using are HS-700BB

any idea what could be the cause..???

thank you again for your help

[Almasri]

By the way that was another question for you Ttelmah

and how did u connect your pic to the Parallax board was it RS232 through the 3-conductor wire or USB

thanks again

[Almasri]

anybody got a website that can help me ...??
or any other resources..?