At 01:08 AM 9/5/2005, Paul Hamilton wrote:
Hi,
I am trying to debug a Mini SSC FreeBSD program that I am trying to write.
It would be nice to be able to be able to see what is being transmitted. It
would help in the debugging of my program.
Here is a link to a Windows based Mini SSC program:
http://www.rentron.com/Mini-ssc.htm Using this, I can control the servo, so
I know the hardware and cables work etc.
I have been using the 'minicom' port to dump the received data. However, it
doesn't seem to collect the data properly. Data coming in should be in
accordance with the SSC protocol, ie:
byte 1: 0xFF // sync byte
byte 2: 0x01 - 0x25f //servo address
How do you fit 0x25f into a single byte? (I count 10 bits required)
byte 3: 0x00 - 0x255 // servo position
Same question as above.
Here is a dump of the collected data (via minicom):
#hexdump minicom.cap
0000000 45ff 49ff 4cff 50ff 53ff 57ff 5aff 57ff
0000010 53ff 50ff 4cff 49ff 45ff 45ff 01ff ff82
0000020 8101 01ff ff80 8202 02ff ff81 8002 03ff
0000030 ff83 8203 03ff ff81 8003 7fff 7fff 7eff
0000040 01ff ff7f 7f02 03ff ff7f ff7f 8001 02ff
0000050 ff80 8003 04ff ff80 ff80 8006 07ff 0080
Looking at the first row of data, it is only showing two bytes, sync and
servo position. Rows 020 and 030, shows some servo addresses, but
sometimes, together! Both the mini-ssc.exe and minicom program are using
9600 8n1, so why is it showing this? Is there something I have missed in
the setup of minicom? Looks like this is a serial buffer problem.
You probably have byte ordering issues. Does something like this
look more reasonable?
0000000 ff45 ff49 ff4c ff50 ff53 ff57 ff5a ff57
0000010 ff53 ff50 ff4c ff49 ff45 ff45 ff01 82ff
0000020 0181 ff01 80ff 0282 ff02 81ff 0280 ff03
0000030 83ff 0382 ff03 81ff 0380 ff7f ff7f ff7e
0000040 ff01 7fff 027f ff03 7fff 7fff 0180 ff02
0000050 80ff 0380 ff04 80ff 80ff 0680 ff07 8000
-Glenn
Is there a better program I could use to display the incoming serial data in
hex?
NOTE: I only use two wires, signal ground and Tx Data (connected to the Rx
Data). The servo does respond correctly, so I know the serial data must be
in the correct 3 byte format.
Looking fwd to your thoughts.
Cheers,
Paul Hamilton
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