Mike
How is your development coming along on the ssc32 NG ?
Wayne
No layouts or software yet, but I have been pondering.
- USB vs RS232 host connection.
- Which processor to use. I have recently been tempted by the dsPIC30 family, which is very powerful and reasonably priced. But the toolset is expensive and the learning curve would slow me down. I’ll probably stick with the ATmega1281.
- How to communicate with digital servos. This will require some testing before I commit to a design.
- Software structure. Big loop versus a real RTOS, how far should I go towards an object-oriented design, changes to the pulse generation now that the shift registers are gone, stuff like that.
- Bootloader requirements.
- What to do with all the new capabilities offered by the new processor.
Also, I have been intrigued by the thought of an I/O expander for the SSC32 NG. This came up in the NG thread a while back, as an A/D input board. But I am thinking of it as a more general I/O expander that offers 8 channels of A/D input, digital I/O, or servo outputs. There is no reason it would need to be restricted to the SSC32 NG either, it could be an I/O expander for a Basic Atom/Stamp on the Mini-ABB. I have been trying to decide whether the I/O expander should come first (with a TTL serial interface for the Basic Atom/Stamp).
But before I do anything concrete on the NG, I need to finish up the SSC-32 update for the ATmega168 processor. Jim is being very patient with me, and I am trying not to get distracted.
Actually, miked, microchip’s MPLAB + C18 are free. Get the student edition and you’ll get free for 60 days. After that it isn’t “as” compressed but it doesn’t affect it much. The dsPIC30 is a nice family, for sure. The PIC18F67J50 and PIC18F87J50 are both interesting devices to look at too. They support USB + USB Bootloader. They are 60, and 80pins respectively and feature 128kb of memory. If you can’t decide between USB and RS232, then use the dsPIC. It has two serial ports. One can have a USB to USART, the other a header to a serial port.
A few weeks ago, Linuxguy pointed me to a kernel system for the PIC18F and 30F. It has events and time management which might be helpful for your software structure stuff.
As for all the capabilities, add pins and commands to access them!
Hi Mike
No layouts or software yet, but I have been pondering.
Yes taking your time means that you will probably be alot more comfortable with the final decisions.
USB vs RS232 host connection.
It seems that the trend is towards laptops and portability recently where USB seems to be becoming more common and rs232 harder to find.
—cut –
Also, I have been intrigued by the thought of an I/O expander for the SSC32 NG. This came up in the NG thread a while back,
Mike would this potential I/O exp work with the current SSC32 ?
Wayne
HI Mike,
The research and trade-offs are always the hard part!
USB would be welcome, but would it be used that often? I have some simple USB to RS-232 dongles that work well for me on my notebook computer, or when I need a couple of extra ports.
YES, the DsPIC is VERY tempting! I’d certainly like to see that. Even an old '18F4550 or '4620 family part.
I don’t know that you need a “real” RTOS, but a real-time clock and running tasks by task flags could certainly push it towards a deterministic design. Object Orientated code? Tends to be bloatware. I wouldn’t think it would be needed anywhere in the near future.
I think we’re most interested in sending blocks of servo commands, which has really made off-SSC32 gait generation possible. That’s probably the most important for us hexapod (all the 'pods) users.
You might consider allowing I2C communication to the SSC32. And if you don’t have it or something similar already, a “comment” (//) start of line token to completely IGNORE extraneous text could be useful. But so far, I’ve sent the SSC32 a LOT of extraneous comments, and it hasn’t taken offence!
Well, since you asked, can the basic gait generator be expanded to 3DoF legs? I won’t ask for 8 legs… yet!
Best regards,
Alan KM6VV
Hi Mike
It seems like LX is moving towards 12v and more powerful motors to move heavier robots with controllers like the sabertooth.
With the ssc32 at approx 6v and the sabertooth at approx 12v, would it be possible to have the ssc ng work with 12v as well as 6v to allow a mobile robot to have a single power supply source of 12v ?
Wayne
it’s not likely. There is no room on the board to hold a regulator capable of dissipating this much heat. The proper way to do it would be a seperate dedicated power supply for it.
I would asume that separate power supplies whould be used with a 6v/12v setup. The ABB/SC32 only needs to communicate to the motor controller via PWM. I guess there’s always an option to design a small step down transformer to allow a single 12v supply run everything. I belive Pete or someone at one time on these forums, talked about designing a circuit board with miltiple power out options. Perhaps this could be a future Lynxmotion product some day as it would apply to several applications.
It could be called a Lynx VMP board (Voltage MultiPlexer)
You could look at something like the power trends modules from TI such as a PT78ST105. Here’s a link to the data sheet focus.ti.com/lit/ds/slts059a/slts059a.pdf. You need to be careful of the minimum 9V input but using a 12V battery or a 3S li-ion pack this might work just fine. they are not real cheap though. 
It might be worth while for those that need specific power supply to offer to pay persons to make it for them. If the market is too small for kits or finished units to be made, then this may be the only way for non DIY types to build their projects. I’d think a high current auto 6v battery charger might have useable components in it for a high current DIY solution.
Yes I was thinking that a 12v source would be used to power it. This type of board would be great for rovers that require several supply voltages for powering ITX boards, SSC-32, cameras and DC motors.
Actually I was thinking this could be an upgrade drop-in for the voltage regulator used on the SSC-32, allowing VL to come from the battery. It does not really address dropping the 12V down to run the servos though.
I wish I had time atm to work up a low-profile switching power supply that would stack with the SSC-32… maybe someone with some free time and a layout tool could bang out a design we could run through batchpcb? 
I can lay it out but we need a circuit designer.
gota love stackable lynx boards!
Any circuit desiners willing to take on this project?
Anyone…?
Anyone.......? :laughing:One might want to consider DC-DC converters. On an old wheeled 'bot I built, the drive was a pair of 48V servos (from Qume printers), and the main battery was 4 x 12V LARGE sealed batteries. For running the electronics, the DC-DC converter converted it down to 5V. An additional tiny 12v converter handled the remainder of the XT-motherboard’s power requirements (I said it was old).
Alan KM6VV
We need to start a new thread in the electronics section of the forums. Look for " Voltage Multiplexer Board "