ServoPod USB

[frontech]

Hi,

I was really excited to see the possiblility of using the ServoPod with a USB port for comm.
I have a couple of question-sets:

1.
Is it USB 1.1 or 2.0?
How much is the throughput in MB/s ?
Is the throughput limited by the clock on Isopod?

2.
When does it officially come out ?
How much will it cost?

thanks for your help,

[RMDumse]

Originally posted by frontech
Is it USB 1.1 or 2.0?


USB 1.1



How much is the throughput in MB/s ?


The inspiration for the inclusion of USB was for connectivity, rather than throughput, so the USB interface comes to the chip as a conversions to a serial interface.


Is the throughput limited by the clock on Isopod?


Yes, limited by the serial speed chosen.


When does it officially come out ?


T.B.D. Late prototypes in operation now.


How much will it cost?


T.B.D. Probably ~$20 over non-USB

[jinx]

So does this mean that the USB is now limited to 38400 Baud, which is what the Isopod currently supports?

I think including a USB 1.1 or 2.0 full controller would really be a benefit to many users and control people. The bandwidth limitation of serial is a serious hindrance to many of us.

thanks,
jinx.

[RMDumse]

Tom had a talk with me, and told me we are about two weeks from production. Also he thinks it will cost a bit more than I indicated, because it is not only an issue of USB being added, but also it has more external memory added as well. He is thinking it will be introduced at $249.

Yes, we will surely continue in making additional USB interfaces in the future if this first effort is well received. Currently, the 1.1 and serial is the easiest step. With so many computers and laptops lacking serial ports in the newest models, we see "the writing on the wall".

We're also beginning to explore ARM processors with both host and slave USB interfaces. These look very interesting.

[panorama]

I too am interested in USB. That it runs off the serial is not an issue for me, but I still have questions:

1) My Isopod app runs a simple loop on start-up, reading some ports and outputting a simple stream of serial data. Will I be able to do this, and how will the host read the data?
2) Is the USB data available to be read via HID? This would be really great, because then drivers would not be an issue, and it would work equally well with Mac's.
3) Can the 'Pod run off the USB power if I am not using too many features of the processor, or do I still need an external power source?

Thanks,
Tim

[RMDumse]

Originally posted by panorama
1) My Isopod app runs a simple loop on start-up, reading some ports and outputting a simple stream of serial data. Will I be able to do this, and how will the host read the data?

Yes.

2) Is the USB data available to be read via HID? This would be really great, because then drivers would not be an issue, and it would work equally well with Mac's.

Sorry, I don' t know what HID is. Host interface device? or some such? Oh. Human Interface Device. Not sure.

But, there are drivers available for both Mac and PC for this FTDI chip. So yes, it will work with both Mac and PC, which may be an acceptable end goal anyway.

3) Can the 'Pod run off the USB power if I am not using too many features of the processor, or do I still need an external power source?

Yes. How it works is the FTDI chip comes up first on the 100mA available, then requests the full power, and applies the 500mA to the 'Pod. The board in all takes about 300mA's so there's a little additional 5V power left over.

So you see, your autostarted program should work fine for this, because communications comes up first, then the processor.

Latest prototypes are doing this, and working well, so we are very near production.

[jinx]

Is there some way for me to know the exact location and dimensions of the mounting holes for the ServoPod X ?
We're designing a case for it and we need the dimensions before we fabricate it.

thanks,
jinx.

[panorama]

Randy,
That's great, but after I wrote my post I realized that the board is too big for my product. Any chance you will have a Plug-a-pod sized (or a little bigger) board using USB in the next 6 months or so?
Tim

[nmitech]

jinx, here is the ServoPod-USB mechanical drawing.
http://www.newmicros.com/store/product_schematics_pdf/Bea02mec.pdf

[nmitech]

Tim, Maybe we can help you to do custom board to fit your application, if you can tell us what is the maximum board size you can live with, and number of IO interface requirements. So we might be able to reduce the board size to fit your needs. To make a DSP807 & USB converter to fit it in a Plug-a-Pod size is almost impossible even with the DSP807 BGA package.

chris

[panorama]

Well, even twice the size of Plug-a-Pod would be ok, but adding the chip to a carrier board might be ok. What USB chip do you use? FT232BM?
Tim

[nmitech]

What USB chip do you use? FT232BM?
Yes! The drivers are available at FTDI. Link attached below,
http://www.ftdichip.com/FTDriver.htm

[panorama]

I found a company, ASIX, who makes a DIP 28 solution called UMS2, with all the necessary parts to make the connection. Since my quantities are small, and I don't do surface mount, this is a good solution for me.

They apparently do not handle RS232, but want TTL serial. Is it possible to connect to the RxD, TxD of the PlugaPod, while the RS232 chip is installed? Or do I need to order it without the 232 installed?

I guess I could use the USB to download my program, so I wouldn't really need the RS232, but I would still rather have it if it works that way.

Thanks,
Tim

[nmitech]

Is it possible to connect to the RxD, TxD of the PlugaPod, while the RS232 chip is installed? Or do I need to order it without the 232 installed?

To use the TTL signals with the RS-232 chip installed, you must disable the receiver, PE3 must set high to make the receiver output into a high-Z state. Other option, cut PE3 trace to pin 1 of Max3221 chip and pull pin 1 high. The simplest way is to order one without the RS-232 driver chip installs

chris

[panorama]

To disable RS232, is it PE3 or PA3? Did you change the controlling pin?

In the past it seems that when PA3 was grounded, the RS232 was disabled, or am I confusing it with something else?

Tim

[nmitech]

From the schematic, it shows PE3 controls the RS-232 receiver (EN), and PA3 controls the RS-232 transmitter (shut down mode). Optional PA3 signal is also brought out to J5 connector for GPIO access. From previous customer feedbacks, most are used PA3 for GPIO instead of RS-232 Power control. Once PA3 is toggled low, the RS-232 transmitter is disable and it will no longer available for terminal access. Therefore, PA3 signal is now removed from pin 16(SHDN) of RS-232 for GPIO access only.

In your case, you need to turn on PE3 high to disable the RS-232 receiver in order to use SCI0 for TTL option.

[panorama]

So I will do "PE3 ON", and then I can use TxD RxD in 5v mode. Is that correct?

Tim

[nmitech]

So I will do "PE3 ON", and then I can use TxD RxD in 5v mode. Is that correct?
Yes, as long as the device that connects to the Plug-a-Pod serial interface can translate 2.6V as VIH. Since the Plug-a-Pod is a 3.3V device, its inputs can withstand up to 5.5V and the output, VOH minimum is VDD-0.7V (~2.6V-3.3V)

[Pacetech]

Originally posted by panorama
I found a company, ASIX, who makes a DIP 28 solution called UMS2, with all the necessary parts to make the connection. Since my quantities are small, and I don't do surface mount, this is a good solution for me.


www.pololu.com makes a USB to TTL Serial that I've been using for a week now on my Plug-A-Pod, running some stuff at 115200 bps.

I also tweaked a few bytes of the S-Record to have the POD comes up at 115200, so downloads are very fast now.

[panorama]

Dear Pacetech,
Thanks for the heads-up.
I need to power my PlugaPod from the USB. Theoretically, I need a mosfet to switch on the power after the USB chip has requested additional power from the host.
I guess you are powering the PlugaPod from an external supply, or did you find that the mosfet is unnecessary?
Pan

[Pacetech]

Originally posted by panorama
Dear Pacetech,
Thanks for the heads-up.
I need to power my PlugaPod from the USB. Theoretically, I need a mosfet to switch on the power after the USB chip has requested additional power from the host.
I guess you are powering the PlugaPod from an external supply, or did you find that the mosfet is unnecessary?
Pan

Well, the USB connection brings in 5V and I did not even read about the MOSFET setup. Somethimes when I tried to power up my board with that, I get a windows error - something like, USB Device is trying to draw too much power and the device stops working until I un-plug and re-plug it.

I'm using a 4 port HUB right now and not plugging into the PC.

My board has a bunch of chips on it besides the POD, but not drawing more than the 500mA limit of the USB. My guess is my CAPs are charging up.

It does work sometimes. So instead of trying to power from the USB, I isolated the USB 5V and my board's 5V, so I just use Tx Rx and GND. The USB device is only powered up when its connected to a PC, which will save me battery power - I will only use the USB for programming and debugging.

[panorama]

You might want to look into the UMS2. It does have the capability of requesting additional power, and providing a signal when it is approved so the uP can be powered up. I have not personally got to that point yet, however.
Pan

[nmitech]

We'll have an USB interface board for Plug-a-Pod/Plug-an-ARM/TiniPod/TiniARM/TiniAVR in about 4 to 6 weeks. Power from USB bus, and optional for external power as well.

[panorama]

Wonderful, if it fits inside my device.
How big will the interface board be, and how will it connect to the Plugapod? Cost? I have designed a board to carry the PlugaPod and the UMS2, and my IO connectors, and mounting holes, and MOSFET, all in 2.7x1.7", which are the maximum dimensions I can live with.

[nmitech]

Our current plan is trying to keep it the same size as the current Plug-a-Pod Interface board, 4"x4". Just add the RS-232 conversion and USB interface circuitry to have the option for USB, or RS-232 DB9 interface.

[panorama]

OK, I just want to check this again. Some months ago, I found that grounding PA3 would cause some problem, I guess disabling the RS232 or something like that.

If I order a PlugaPod today, will it still do this, or have you changed the PA3 pin to GPIO only? I can't test it, because I only have the old type here right now.

Tim

[nmitech]

have you changed the PA3 pin to GPIO only?
I will double check with NMI's production manager to makesure all Plug-a-pod has PA3 configures for GPIO only when shipping out.