Directly Control KHR-3HV servos using RB-110

2011-05-24T08:38:09+01:00

Hey i-Bot,

Yes, the problem is we need 2 Com ports with TXDEN but RB110 only has 1, i.e. COM6.

Supporters of RB110 also suggested to discard the message sent by itself (see blow). I will try this method first.
http://robosavvy.com/forum/viewtopic.php?t=7225

Regards,
Jie

Statistics: Posted by goodma — Tue May 24, 2011 8:38 am

Directly Control KHR-3HV servos using RB-110

2011-05-23T14:17:37+01:00

Did you read the thread here ?
http://robosavvy.com/forum/viewtopic.php?t=6374&start=0&postdays=0&postorder=asc&highlight=

My understanding is that the ports 5 and 6 on the RB110 are provided by an on board FT2232H device. Also port 6 exposes the TXDEN pin.

The baud rate should be almost exact at 115200, and only about 1% out at 1.25MHz.

Statistics: Posted by i-Bot — Mon May 23, 2011 2:17 pm

Directly Control KHR-3HV servos using RB-110

2011-05-23T11:43:13+01:00

I am now trying to directly control Kondo's servos (KRS-2552HV) using the COM ports of RB110, has anyone got the idea of the following questions?

1. The TTL level of COM3, COM4 and COM5 are 3.3v; but are they 5v input tolerant? In other word can they accept 5v logic input without any problem?

2. COM6 is a 10-pin general serial port, but how can I use it as another TTL port (such as COM5) please? I know I can use a RS232-TTL converter but is there a better way, such as using a special driver from FTDI?

I think I've understood the logic system of RCB-4, see below:

[Original USB]o---1---o[RCB-4]o---2---o[SIO1-4]
o ---3---o[SIO5-8]

RCB-4 has 3 serial ports. COM1 communicates with the original FDTI USB with inverted 3.3v logic. ``Hidden'' COM2 and COM3 control two groups of servos with 5v logic. We have managed to control RCB-4 without problem (using 7404). I am now thinking about a more challenging task --- to completely get rid of RCB-4 and directly control all the servos, like this:

[RB110]o---COM5---o[SIO1-4]
o---COM6---o[SIO5-8]

If RB110 supports 5v logic input that would be great --- I can simply use a single 7404 to boost its 3.3v output to 5v for both COM5 and COM6, so servos can understand it. Otherwise I need to use the ``Logic Level converter'' such as txb0104 --- it requires more physical space as it needs both 5v and 3.3v VCC from RB110.

http://focus.ti.com/lit/ds/symlink/txb0104.pdf
http://www.maxim-ic.com/app-notes/index.mvp/id/3007
http://www.microchip.com/stellent/group ... 026368.pdf

BTW, I've managed to directly control a single 3HV servo without any logic conversion but the risk is more servos will pull down the 3.3v logic to about 2.5v so it may not always work while the robot is running. Another problem is if I short TX and RX from the RB110 side, it will always receieve the message from itself, I know 74125 can solve this problem but COM3-COM5 don't come with the TXDEN pin.

Statistics: Posted by goodma — Mon May 23, 2011 11:43 am

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Directly Control KHR-3HV servos using RB-110

Directly Control KHR-3HV servos using RB-110

Directly Control KHR-3HV servos using RB-110