OpenServo.com

mog123 · Joined: 07 Jun 2009 Posts: 12 Location: Poland

Hey, I'm trying to get into the openservo project.

Why can't I just download the app on the atmega while it's soldered on the opeservo board, but I need the USB/TWI interface?

Also, how does controlling the openservo by SPI look?
The website mentions SPI control by daisy-chaining but I haven't found any info on that.

jharvey · Posted: Sat Nov 28, 2009 3:33 pm Post subject:

The OSV3 can be programmed from a blank ATMEGA chip with the OSIF. Once the initial firmware is installed, it can be updated to future firmware by bootstrapping it over the I2C comms. So yes you can solder up your own board and program it.

The OSIF interface can command and bootstrap the OSV3, or OSV2 by I2C. If you have the extra wires installed, the OSIF can also program by using the the ICP interface.

If you don't have the OSIF, you can use another device for the I2C, or ICP communications.

Only 4 wires are required for I2C communications. PWR, GND, SCL, SDA.

I don't know all that much about SPI. Don't I recall something like I2C is Philips/NXP's name for SPI or something like that.

kbb · Joined: 01 Jun 2007 Posts: 180

mog123 · Joined: 07 Jun 2009 Posts: 12 Location: Poland

Hmm, the V3 is too complicated to be made at home so I wanted to do the V2...

Is there any free/opensource/cheap-diy USB->I2C adapter?

jharvey · Posted: Sun Nov 29, 2009 12:39 am Post subject:

The OSIF is fairly low cost, and associated with OpenServo. See http://robotfuzz.com/OSIF

That device can be built as well. I think getting the initial firmware on it is a bit hard. I know it can do the I2C and program a blank chip.

mog123 · Joined: 07 Jun 2009 Posts: 12 Location: Poland

How about this ?
http://www.electronics-lab.com/blog/?p=531

jharvey · Posted: Tue Dec 01, 2009 11:13 am Post subject:

I don't see any physical problems. It appears like it might be the OSIF in a slightly different package. It's an AVR with USB and I2C. They appear to have used an AVR with less pins and less capabilities, but it's basically the same thing. I'm not sure what firmware they install on it, or if you build it yourself, what firmware you have to install on it. To build that you'll need some kind of AVR programmer.

If it doesn't use the same drivers as the OSIF, you will need to write a fair bit of code from scratch. The OSIF has some pre-written software that allows for a quick check that things are working and in good order.

If you want to role your own, there is a fellow on here with blank OSIF boards. I think he would sell those for a couple bucks. If you build your own OSIF, I believe you will need an AVR programmer as well. But if you purchase it, it comes with firmware pre-installed.

About the V2 board, sparkfun sells those.
http://www.sparkfun.com/commerce/product_info.php?products_id=9014

Hey look at that, I2C is different than SPI. Thanks for the note.

mog123 · Joined: 07 Jun 2009 Posts: 12 Location: Poland

Hey, is there any modified version of the v2 pcb for the mg995? I just opened it and the board is really much much shorter and it won't fit the whole v2.

About the osif. How can i contact that guy that sells the pcbs?

jharvey · Posted: Wed Dec 02, 2009 9:50 am Post subject:

Barry, goes by ginge here. He sells them via http://robotfuzz.com/OSIF I see he has a "contact us" link on his page there.

I believe you can trim the V2 board, then add some jumper wires.

For the MG995 to get the extra power, they had to make the motor as large a possible. If you don't need the extra torque, most don't really need that much power, you can use a different servo, that has a shorter motor, and allows the PCB to fit.

mog123 · Joined: 07 Jun 2009 Posts: 12 Location: Poland

Yeah, I realized I could trim the pcb down, and jus solder the wires to the open servo board.

It's all coming together now Smile