RX-64 Issues

[JonHylands]

So, I decided to start playing with my RX-64 last night. I cobbled together an interface on a breadboard with an FT232 and a MAX1487 (high speed RS-485 interface chip). I am actually talking to the servo, because I get a well-formed response back, but the only response I get back is 1, which means (looking at the error table) "Input Voltage Error".

I'm feeding 18 volts into the servo, and when I power it up, I get the double LED flash. Both LEDs on the FT232 interface are blinking (transmit and receive), and like I said I'm getting a fully formed response back, including the checksum.

The voltage limits on the servo are listed as 12 - 24 volts, with 18 volts as the "standard".

Has anyone seen anything like this before?

- Jon

[Robo1]

Can you get the servo to move yet!

What command are you trying to send to the servo.

What are you talking to the servo from, a PC!

What software are you running.

Bren

[JonHylands]

I'm using my own software, that I use to talk to AX-12 servos. The command language is identical, its just the transport mechanism that is different. I'm running on my PC, talking to an FT232 through a virtual serial port.

It doesn't matter which command I send, I get the same response.

I'm sending this: FF FF 01 02 01 FB

I get back this: FF FF 01 02 01 FB

Heh. Okay, now I know what's going on. I've never looked at the request and response side by side. I'm seeing the echo of my request, which means the servo isn't getting it.

Thanks for pushing me to explain further in depth...

- Jon

[Robo1]

This could help!

The software that I use to run my DX's I think came from you! It's the Gumstix serial example. I have just my gumstix hook up to my MAx485 With the directional wire held high. So I don't get a reply yet but using that serial software I just set the code "FF FF 01 02 01 FB" using that. What does the signal look like have you scoped it.

Bren

[JonHylands]

No, I don't have a scope. Right now I'm not running this on the gumstix, just directly from my PC.

When you say "With the directional wire held high", what does that mean? Which pin on the MAX485 are you holding high? Both 2 and 3? Are you shorting them together?

- Jon

[Robo1]

What 485 chip are you using I use a max485 it's the same chip that's in the DX manual. Here.
Page 7. It has 8 pins, the two pin's RE/DE which are the direction selector I tried them together. You pull it high to send and pull low to receive.

Bren

[JonHylands]

I'm using the MAX1487, which is in the same family, and pin-compatible.

- Jon

[Robo1]

Have you tried all the different serial speeds. Have you tried using 0xFE for the servo address. Some of my servo came in different default serial speed setting and random ID numbers.

Bren

[JonHylands]

Robo1, I owe you a beer

57,600 baud is the magic number...

Thanks for the help!

- Jon

[JonHylands]

So, interestingly, I can use the same software (like, exactly the same) to drive an RX-64 as I use to drive an AX-12.

I was thinking that would be the case, since the control table is the same, but it was nice to see it actually in action...

One really nice thing about the RX-64 - no annoying squeal...

- Jon

[Robo1]

RX-64 = Lovely

I think I will have to try them for my next bot. Hopefully I will finish my bot my next weekend. But I've been saying that for the last 2 months .

It always takes longer then you think.

Bren