New Brainbot
New Brainbot
by JonHylands
Fri Sep 28, 2007 12:17 am
I'm in the process of putting together a second BrainBot, this time using a one-piece printed chest instead of machining it. I'm really happy with how it is all working out...
This weekend or early next week I'll be putting together the third one, also with a printed chest, and with a tracked base.
- Jon
This weekend or early next week I'll be putting together the third one, also with a printed chest, and with a tracked base.
- Jon
by Dewey
Fri Sep 28, 2007 4:04 pm
Jon
Like the idea of a larger main Torso. The Robotis stock mouldings may be neat but there is no space for addins/addons.
Everyone, myself included seems to have the Torso to leg rotation servos connected such that all the load is a shear on the top servo bearing. It would seem better from a loading point of view to utilse a U bracket arrangement, as most other joints.
I admit I can't see how to do this with any acceptable geometry. What are your thoughts on the loading on these servos?
Dewey
Like the idea of a larger main Torso. The Robotis stock mouldings may be neat but there is no space for addins/addons.
Everyone, myself included seems to have the Torso to leg rotation servos connected such that all the load is a shear on the top servo bearing. It would seem better from a loading point of view to utilse a U bracket arrangement, as most other joints.
I admit I can't see how to do this with any acceptable geometry. What are your thoughts on the loading on these servos?
Dewey
by JonHylands
Fri Sep 28, 2007 4:17 pm
The main advantage to the larger chest is the ability to put a head yaw servo inside the chest, between the shoulder servos.
As far as the hip yaw servo, I don't see any problems with the way it is done - you have a lot more trouble with the weight on the hip roll servo than the hip yaw servo (the one you're talking about). The robot doesn't weigh enough
If you were building a larger, heavier bot, I would use either a thrust bearing or a tapered roller bearing, and have the servo drive the rotation, but not hold any of the weight.
- Jon
As far as the hip yaw servo, I don't see any problems with the way it is done - you have a lot more trouble with the weight on the hip roll servo than the hip yaw servo (the one you're talking about). The robot doesn't weigh enough
If you were building a larger, heavier bot, I would use either a thrust bearing or a tapered roller bearing, and have the servo drive the rotation, but not hold any of the weight.
- Jon
by JonHylands
Mon Oct 15, 2007 7:14 pm
So last night I finally got wifi running with the gumstix, and now BrainBot can tool around completely wirelessly. Today at lunch I made a short video of BrainBot driving around my driveway (I'm controlling it with a joystick attached to my PC).
The tracked base is being controlled with one of my bus I/O boards, using PWM through a Dimension Engineering motor driver board. The I/O board is controlled from the gumstix, which forwards commands from my PC over wifi to the bus device using an FT232.
Finally, the dream is here: 1.0 Mbps wireless from a PC to the Bioloid bus...
- Jon
phpBB [media]
The tracked base is being controlled with one of my bus I/O boards, using PWM through a Dimension Engineering motor driver board. The I/O board is controlled from the gumstix, which forwards commands from my PC over wifi to the bus device using an FT232.
Finally, the dream is here: 1.0 Mbps wireless from a PC to the Bioloid bus...
- Jon
by JonHylands
Mon Oct 15, 2007 10:51 pm
I'm not using the UART on the gumstix to talk to the bus. I'm using a virtual serial port running through one of the host USB ports. This is connected to an FT232 chip, which interfaces directly (using a tristate and inverter) with the bus.
I open the port from the gumstix at 1,000,000 baud, which the USB interface can do easily.
There is no USB network. The network is between the gumstix and my PC, and its wifi (802.11g) running somewhat faster than 1.0 Mbps.
The devices on the bus all have AVR chips inside, including the AX-12. My devices use ATmega168's, which can connect to the serial line in the bus directly, with no added hardware required.
- Jon
I open the port from the gumstix at 1,000,000 baud, which the USB interface can do easily.
There is no USB network. The network is between the gumstix and my PC, and its wifi (802.11g) running somewhat faster than 1.0 Mbps.
The devices on the bus all have AVR chips inside, including the AX-12. My devices use ATmega168's, which can connect to the serial line in the bus directly, with no added hardware required.
- Jon
by Robo1
Tue Oct 16, 2007 11:54 am
Hi Jon
I know this is a bit cheeky but could I possible have a look at the code for the virtual serial port. I'm writing the code at the moment for my gumstix to talk to my DX-117's and want to run them at there fall speed of 1 mbps. Is it similar to your example SPI bit bang code.
Bren
I know this is a bit cheeky but could I possible have a look at the code for the virtual serial port. I'm writing the code at the moment for my gumstix to talk to my DX-117's and want to run them at there fall speed of 1 mbps. Is it similar to your example SPI bit bang code.
Bren
by JonHylands
Tue Oct 16, 2007 1:38 pm
Its just the linux driver for the FT232 - that's how it works. It creates a device called ttyUSB0, which you can access just like any of the other serial ports, except you can open it a 1.0 mbps.
To talk to the DX-117 (or the RX-series), you need the FT232 chip, plus an RS-485 chip (I just picked up a couple MAX1487 chips from Digikey for this). The FT232 data sheet has a nice schematic showing how to hook it up.
Once you get that, let me know, and I'll point you at the FT232 drivers for the gumstix. Are you set up to compile stuff like this on the gumstix? My brother takes care of that for me, so I just end up copying the binaries over, but depending on what buildroot you are using you need to recompile stuff.
- Jon
To talk to the DX-117 (or the RX-series), you need the FT232 chip, plus an RS-485 chip (I just picked up a couple MAX1487 chips from Digikey for this). The FT232 data sheet has a nice schematic showing how to hook it up.
Once you get that, let me know, and I'll point you at the FT232 drivers for the gumstix. Are you set up to compile stuff like this on the gumstix? My brother takes care of that for me, so I just end up copying the binaries over, but depending on what buildroot you are using you need to recompile stuff.
- Jon
by Robo1
Tue Oct 16, 2007 4:42 pm
Cheers for that Jon
I've just got my gumstix talking to my DX's
. At the moment I'm just using the stuart and a max485. In your setup is it going
Gumstix
|
FT232L
|
FT232L
|
MAX485
|
Servo
How fast can you make the Gumstix talk to the USB. Do you use the same usb line to talk to the other atmels. After thinking about this afternoon it does seem like a good way to link up different parts, as I'm using SPI line to talk to the sensors (Arduino) and the stuart talking to the servos. But having them on one fast bus would be better. Is there anyway of buffering the signal at the other end to stop the bottle neck.
Bren
I've just got my gumstix talking to my DX's
. At the moment I'm just using the stuart and a max485. In your setup is it going
Gumstix
|
FT232L
|
FT232L
|
MAX485
|
Servo
How fast can you make the Gumstix talk to the USB. Do you use the same usb line to talk to the other atmels. After thinking about this afternoon it does seem like a good way to link up different parts, as I'm using SPI line to talk to the sensors (Arduino) and the stuart talking to the servos. But having them on one fast bus would be better. Is there anyway of buffering the signal at the other end to stop the bottle neck.
Bren
by JonHylands
Tue Oct 16, 2007 5:59 pm
No, mine would be:
Gumstix
|
FT232L
|
MAX485
|
RX/DX servo
The gumstix can talk over the USB port at 1.0 mbps.
Right now I'm using AX-12 servos, so my setup is this:
Gumstix
|
FT232L
|
Tristate/inverter
|
AX-12 servo/IMU/IO Board (any bus device)
Which end are you referring to for buffering, and what bottleneck?
- Jon
Gumstix
|
FT232L
|
MAX485
|
RX/DX servo
The gumstix can talk over the USB port at 1.0 mbps.
Right now I'm using AX-12 servos, so my setup is this:
Gumstix
|
FT232L
|
Tristate/inverter
|
AX-12 servo/IMU/IO Board (any bus device)
Which end are you referring to for buffering, and what bottleneck?
- Jon
by Robo1
Tue Oct 16, 2007 10:07 pm
I will look in to usb and the FT232L in more detail tomorrow but would be very interested in it if we can push it above 2-3mbps then you could have a couple of atmel chips running of it.
What I meant by bottle neck is if you can get the usb bus faster then 1mbps then there will be a bottle neck of the 1mbps speed limit to the servos.
Bren
What I meant by bottle neck is if you can get the usb bus faster then 1mbps then there will be a bottle neck of the 1mbps speed limit to the servos.
Bren