PDA

View Full Version : [Question(s)] Axon to SSC 32



WGhost9
06-25-2009, 10:18 AM
Well its the summer and that means it is time to start a new robot project!

For my next robot, I am interested in using an Axon microcontroller, but, due to current demands in the 20+ amp range, the Axon will be unable to handle all of my servo needs. Hence, I am thinking of connnecting the Axon mcu to a spare ssc-32 from a now defunct robot of mine.

My question is how, if at all possible, might I be able to connect the two boards together and what might the code look like for axon control of a ssc-32?

Adrenalynn
06-25-2009, 11:40 AM
You could run a separate power and ground to the servos, share common ground with the Axon, and take signal from the Axon.

That said - sure, the Axon has three available serial ports. Connect 'em up, make sure they share common electrical ground, then just send SSC32 control strings out the serial port it's connected to.

My arm controller does the same thing, only over XBee serial link, from the Arduino.

ScuD
06-25-2009, 11:42 AM
I don't know the Axon so I can't help you there, but if I understand correctly the problem is simply in the power drawn by the servo's, and not the amount of servo's that can be controlled by the Axon?

In this case you could also splice the servo cables and supply power to them separately from the Axon board.
Just make sure your power supplies are properly grounded and bypassed and it should work fine.

But then offcourse you are splitting up perfectly good cables..

WGhost9
06-25-2009, 12:39 PM
I was planning on using the UARTs but I am uncertian of their voltage level. Would i connect them to the TTL or RS232 input of the SSC32. Also, i think the coding for the UARTs looks like:

uartSetBaudRate(1, 115200);
rprintfInit(uart2SendByte);
rprintf("P0 #1500 <cr>\r");

but I am unsure how to set the flow rate, stop bits, etc. settings.

As per simply cutting into the power supply of the servos, that is one simple solution that honestly escaped me :) I will consider doing that, however, I am tempted to go with using the ssc32 I have lying around, simply in the interest of elegance.

Adrenalynn
06-25-2009, 01:33 PM
I think you want to reference the manual (or my SSC32 serial tutorial) for that command string. And <cr> is carriage return, which is \r.

If you connect them together via TTL, then the levels will be TTL.

mannyr7
06-25-2009, 02:20 PM
Replace Bot Board with MCU of your choice and send serial strings to SSC-32.

http://www.lynxmotion.com/images/assembly/ssc32/ssc32m02.gif

WGhost9
06-25-2009, 04:26 PM
So <cr> and /r are indeed one and the same. Also, it seems the consensus here is that I can connect to the UART of the Axon to the TTL outputs of the SSC after all. This is good news. I was worried some sort of converter board may be required. Thank you all for the advice.

Adrenalynn
06-25-2009, 04:56 PM
Make sure you check the rest of that command string too.

jes1510
06-25-2009, 08:52 PM
Keep an ASCII chart handy. They are incredibly useful:
http://www.asciitable.com/

carriage return also equals decimal 13. THis means if we send a decimal 13 down the serial port then the SSC32 will interpret it as a carriage return. Note that you don't want to send the number "1" and then "3". You need to send the binary equivalent of 13 which is 1101.

It could be done like so in Python (modified from the PySerial docs):
>>> import serial
>>> ser.write("Hello World") # Simple enough
>>> ser.write(chr(13)) # Send a carriage return
>>> ser.close() # close portIt's just another way to think about it...