Radio Modems

[ChuckDickerson]

Does anyone have the connector pin-out diagram for the IFI/Ewave RS-422 radio modems? I have checked the IFI and Ewave web sites and the closest thing I can find is in the Ewave RF Modem Tech Manual: http://www.electrowave.com/downloads...em_techman.pdf section 3.2 pg. 7 that has the standard RS-232 pin-outs and says see the Ewave website for the Screamer422 RF modem pin-outs. I can't find any info on the RS-422 pin-outs on either site. Also, does anyone have any info on the "RM2000" mode used by these modems?

I have a side project that I am using an IFI RC & OI and the standard modems for but would like to have more range than the typical 300' using the IFI/Ewave RF modems. I am considering testing out a pair of these: http://www.maxstream.net/ specifically one of these: http://www.maxstream.net/products/xs...g/9xstream.php or these: http://www.maxstream.net/products/xtend/pkg/9xtend.php but they are fairly expensive so I would like to know if they will work before I fork over the $$$. From what I have read I don't see why not but I can't seem to figure out the pin-outs on the IFI RC/OI radio modem ports so I wouldn't know how to make the interface cable if I purchased the MaxStreams. Has anyone else ever tested any of these MaxStream RF modems in RS-422 mode with the IFI control system? Any help greatly appreciated.

[Rickertsen2]

Looking at the datasheet, the e-wave modems are not completely transparent. They require special commands to configure things such as what channel they operate on. Even if you get another modem and get the pinout right, chances are things won't work unless it uses the same command set as the e-wave modems.



The only solution i can think of is a bit bootleg. It requires a pair of the e-wave modems in series with some third party modems such as the ones you listed above. The second modem must be completely transparent (that is it requires no special commands sent to it to configure it).

[Joe Johnson]

I am not sure but I THINK the configuration stuff is one way communication to the radios. Meaning the OI & RC send the radio configuration info (channel, etc) but I the radio doesn't necessarily send data back to the OI or RC. After config, I think it goes into Rx/Tx mode where all the packeting stuff is handled (CRC checks, etc.)

If I were you I would e-mail Paul at E-wave. He has been pretty supportive of side projects in the past. Alternatively, e-mail Zondag from the Killer Bees, aside from being a great guy and the heart and soul of Team 33 AND the coding Guru for the Bees, he did a reverse engineering job on the FIRST radios back a few years ago. If you convince him your intentions are legitimate, he may share some of what he discovered. I can't promise but it never hurts to ask.

Oh yeah, while I am thinking about it, you don't have to stay with RS-422 radios. $49 or so will get you a converter from RS-232 to RS-422.

Good luck.

Joe J.

[ChuckDickerson]

Originally Posted by Joe Johnson

I am not sure but I THINK the configuration stuff is one way communication to the radios. Meaning the OI & RC send the radio configuration info (channel, etc) but I the radio doesn't necessarily send data back to the OI or RC. After config, I think it goes into Rx/Tx mode where all the packeting stuff is handled (CRC checks, etc.)

If I were you I would e-mail Paul at E-wave. He has been pretty supportive of side projects in the past. Alternatively, e-mail Zondag from the Killer Bees, aside from being a great guy and the heart and soul of Team 33 AND the coding Guru for the Bees, he did a reverse engineering job on the FIRST radios back a few years ago. If you convince him your intentions are legitimate, he may share some of what he discovered. I can't promise but it never hurts to ask.

Oh yeah, while I am thinking about it, you don't have to stay with RS-422 radios. $49 or so will get you a converter from RS-232 to RS-422.

Good luck.

Joe J.

Thanks Joe. I have taken your advice and had an email exchange with Paul at Ewave. He is a nice guy and has been very helpful. I asked if he minded me sharing his information with the FIRST community for everyones benefit and he said it is public domain so I should feel free. So for everyones benefit here is what I have found out. I have a PDF of the RS-422 pinouts on the modems. To summarize:

DB9 Male
pin 1 - GND
pin 2 - RS422TX+
pin 3 - RS422RX+
pin 4 - 422POWER (Input 7.2 to 10.5 Volts, 150mA typ.)
pin 5 - GND
pin 6 - RADCTL_422 (Set High - 5V for data mode, Set Low for command mode)
pin 7 - RS422RX-
pin 8 - (No Connection)
pin 9 - RS422TX-

And to quote Paul's email reply:

"...here is the packet specification for the Screamer 422.

This has always been an OEM product, so you will have to put some work into
understanding the documentation.

The SCREAMER422 has a subset of the commands that are listed in the Ewave Technical
Manual that you can download from our web site. If you issue a command that is not
supported by the Screamer422, you will get an "ER" response.

The initial baud rate for the SCREAMER422 is set at 19200 N81.

The Packet sizes are fixed at 26 bytes long. The packet format is as follows:

0xFF, 0xFF, then data bytes 1 through 24. Transmission starts after the last byte
in the series is received. (26 bytes total including the 0xFF, 0xFF start
sequence.) If two consecutive 0xFF are received this is considered a packet header,
and any bytes that were being assembled into a packet are discarded, and the modem
then starts putting back together the 26 byte packet. All 26 bytes are recreated on
the receiving modems end, and transmitted out its serial port.

You may not have consecutive 0xFF in the 24 byte data portion of the packet.
..."

Other than this the only interesting tid bit of info I have found out is that there is no CRC check performed on the 26 byte data packets.

I believe I now have all the information I need to proceed with my project. I have purchased one of these: http://www.maxstream.net/products/xt...kit/9xtend.php from Ebay new in the box for a great price. If this doesn't work out I will have gotten my moneys worth out of the learning experience and will still have the development kit for some other project later. If anyone else has any interest in knowing if these long range modems will work with the IFI RC and OI post your questions here and I will try to answer the best I can. Give me a couple of weeks for the units to arrive and for me to have time to play with them. I hope this info helps other folks as well! Zondag, if you are reading this thread and have any bits of wisdom you would like to share please jump in.

Thanks again,
Chuck

[Dave Flowerday]

As an alternative, you could use the tether port instead. It has RS-232 on it and I'm nearly certain that the command handshaking which is sent to the radio modem is not sent when using the tether. Also the OI and RC switch to tether mode when they see a certain tether pin pulled high. We did a project a few years ago where we built ourselves a field control system, and to do it we used old PBASIC RCs at each end of the field and a control computer which talks to them over the tether port using RS-232 (pretending to be an OI).

It's been a few years since I looked at this but you should be able to figure out which pin fairly easily.

It's worth pointing out for anyone following along in this conversation that attempting these types of things will probably void your IFI warranty. If you hook things up to the wrong pins there's a good chance you can do damage.

Originally Posted by DeepWater

Other than this the only interesting tid bit of info I have found out is that there is no CRC check performed on the 26 byte data packets.

As a side note, the RC does checksum the data after it is received (there are two checksum bytes in each packet), so corrupted data shouldn't be a concern. I assume the checksumming is not done in the modem for latency reasons. If the modems you're looking to use have a config option for it, I'd turn off any checksumming and retransmission that they may do to achieve the best latency.