Among my other projects today was to take one of the new SX48 Proto boards and rig it up to go on my spare BOEBOT.  I took 18 pins worth of .100 single line sockets an set them for RE, RD, RTCC and MCLR. 16 pins worth for RC and RB and an 8 pin for RC. I set a line of 7 pins worth of single line header for the  servo GNDs and the Servo +V Vdd/Vin selector and a two row 4 pin header for the 4 +V and data lines on the servo. Then a 4 pin socket for the Servo data pins as well. I plan to buy one of the small breadboards hat parallax uses on the BOE and glue it down inside the 'fence' made by the pins I put in place.

I then took some simple BS2 code from Robotics 2.2 and brought it over and fed it into the SX/B, hooked up the servos and 'voila' it worked. It took a little extra figuring to get the PULSOUT numbers right but it came alon after awhile.  The SX48 at 50 MHz really cooks along and may make for some very interesting robotics projects.

I will take some pix and post them in a day or so.

Thanks Parallax for an absolutely great product. These boards are gonna sell a lot of SX48's I will bet!

We made that board to fit the Boe-Bot chassis so we could have some SX/B robo-fun.  Here's a program that might interest you: it will control two servos and two IR Leds in the Interrupt -- no more worring about updating servos every 20 ms; it's done for you (Note: I liberated this code from my pal Guenther and converted it to SX/B).

[Quoting: "Jon Williams (Parallax)"]We made that board to fit the Boe-Bot chassis so we could have some SX/B robo-fun.  Here's a program that might interest you: it will control two servos and two IR Leds in the Interrupt -- no more worring about updating servos every 20 ms; it's done for you (Note: I liberated this code from my pal Guenther and converted it to SX/B).

 Once again Parallax support shows its colors ...

[Quoting: "Jon Williams (Parallax)"]We made that board to fit the Boe-Bot chassis so we could have some SX/B robo-fun.  Here's a program that might interest you: it will control two servos and two IR Leds in the Interrupt -- no more worring about updating servos every 20 ms; it's done for you (Note: I liberated this code from my pal Guenther and converted it to SX/B).

2 - I don't have anything that will clock at 8 MHz (why that value???) If I use a 4 MHz resonator and change "RETURNINT 104" to "RETURNINT 52" that should fly???

3 - Similarly, if I use the 50 MHz resonator (I have plenty of them) I would set a pre-scale value and set "RETURNINT" to the appropriate value
4 - It took me a while to get the sense of the code, but I did, EXCEPT, I don't see the IR sensor function. In the beginning of the ISR you do
ISR_Start:
 IR1 = ~IR1                                        ' toggle IR bits
 IR2 = ~IR2    
and that's the last we see of the IR sensor code ... did I miss something?

Brian,
 1 - Yes
 2 - If you use "RETURNINT 52" that will drastically reduce the number of cycles the main code gets. If you leave the SX-Key connected you can use whatever freq you want.
 3 - Yeah, that would be a better idea.
 4 - The ISR code just modulates the IR LEDS. The main code has to check if it "sees" anything, and act accordingly.

Bean.

Brian,
If your application desires reduced battery consumption you might want to consider not using the 50 MHz resonator and prescale approach, but a slower clock.

Guenther summed it up well and I will paraphrase. If you are running the SX a lot faster than you need to, it is like driving a car at 30 mph in 1st gear and the engine is at red-line...Compared to a slower clock speed its would be like driving the same 30 mph in 4th gear and the engine rpm will be much lower.

I find 20MHz is a good comprimise for speed and current.
Bean.

[Quoting: "Jon Williams (Parallax)"]We made that board to fit the Boe-Bot chassis so we could have some SX/B robo-fun.  Here's a program that might interest you: it will control two servos and two IR Leds in the Interrupt -- no more worring about updating servos every 20 ms; it's done for you (Note: I liberated this code from my pal Guenther and converted it to SX/B).

I guess I know  the answer ... FWIW, that is brilliant!!!! It sure simplifes all kinds of things. The two most time/resource hogging aspects of the robot servo stuff is the FREQOUT for the IRs and PULSEOUT to the servos. They don't leave a lot of time to do anything very smart in the normal single threaded mode of the Stamp. Now instead of having to push  through 5-10 20ms PAUSES to do a few PULSOUTs then take a quick peek at some sensor only to rush back to keep the wheels moving I feel I have the room to try all kinds of things. I can pause to let the main routine to 'think' on more sophisticated navigation/activity/sensor matters only 'having' to go back when I determine the need to change direction and/or speed.

Once again ... BRAVO, both to you and to Gunter!

Well, I finally got some time to get back to my SX Robotics today. When last I communicated I had setup the SX48 Protoboard with headers and was awaiting the breadboard in a Parallax order and some 8 MHz resonators from Mouser.

Here's what I have on the SX48 Protoboard
(1) a single row of 16 female headers soldered into RC/RB along the bottom edge of the board
(2) a single row of 18 female headers soldered RD/RE/RTCC/MCLR
(3) a single row of 8 female headers soldered into RA
(4) a single row of 7 male headers soldered to the 4 Vss pins of the Servo connector and the 3 pin Vin/Vdd select for the servo power
(5) a double row of four male headers for the Power and signal lines of the servo
(6) a single row of 4 female headers for the servo data access
(7) a double row of 5 female headers for Vdd and Vss
(8) a small Parallax breadboard we are used to seeing on most of the demo boards, BUT, I had to take a chop saw and remove two rows of holes (the servo connections intrude into where it would otherwise fit unmodified, even if I moved the female headers out one more row I would still lose at least one row of the breadboard) Rotating it the way it would fit unmodified presents pins in a way awkward to wire up for sensors.

I have uploaded two photos, DSCN7599.jpg shows the board mounted on a robot chassis and you can see the whole setup. DSCN7600.jpg is a closuep of the area described in (4) through (7) above.

I also cranked up Jon's program SXBOT.SXB and got it running, I have no IR stuff running yet, thats my next project. But I did get his code running as is, then proceeded to create some subroutines for motion, GoForwardFast, AboutTurn, LeftTurn, etc. The routines make fixed behaviour a snap, its more like script writing than programming. I have uploaded that code, as BBRSXBot.SXB,
Jon, and Gunter, great work ... everyone else, enjoy. I will post my results when I get the IR avoidance and some line following stuff going.

And thanks for the discussion about frequency.   I have been trying to figure out what to do as I have one 4Mhz and several 50Mhz.

I am trying to convert my Toddler to an SX-52 with an SX-28.

Regarding power consumption.
The specifications for the SX-28 indicated the 50mhz pulls somewhere around 75 millamps; while the 4 mhz pull around 7 millamps.  
Also, from what I have read, it seems that square waves are full of nasty harmonics [far more than in sine waves] and going above 50mhz may begin to get you into EMI problems and possibly RFI generation. [Am I correct on this?] If you have to go there, you can build shields and filters and such, but if you don't need it = why bother? Additionally, the SX=52 gets darned hot.

Regarding the generation of IR, it seems that you really could do that with a 555, an oscillator or something similar and free up a lot of computational power.  You may run it in burst and trigger the bursts from software.  
Since PWM takes so much, I have piggybacked a SX-28 on my SX-52 board.  I guess I can run both at 8mhz.  I am a bit worried about using two oscillators on the same board and I am beginning to think I should either have the SX-52 drive both directly, or use the SX-52 to somehow indirectly drive the SX-28.

I seem to get so caught up in hardware that I never get down to code.  Any suggestions?  Initially, I will just try two 8mhz osc.