Connecting to the RS Media Linux Console Port

Here's a quick how-to for patching in to the Linux console port on the RS Media. Thanks to Nocturnal's careful dissection and documentation of the boards inside the RSM, we have easy access to a 3.3 V serial port on the media board, which is located under the panel behind RSMs head. Before you get started, you need to decide on what type of interface you would like to use between your computer and the RSM. Since this port is run at 3.3V on the RSM, you can't simply hook up an RS-232 cable to your computer's serial port - the 12 volt signals are guaranteed to fry your RSM! Nocturnal's approach was to use a Bluetooth wireless serial port module, which avoids the need for voltage adjustments. By the way, I highly encourage you to read Nocturnal's account, and pay heed to his warnings!

Since I have been working with the Parallax Propellor chip (a 3.3V microcontroller), I already had on hand the Prop Plug, a $24 USB to 3.3V serial adaptor.

Prop Plug

To use this with RSM, only 3 wires need to be soldered- Rx, Tx and VSS (ground). For convenience, use a bit of 0.1" pin header material and some 3 conductor wire in your RSM; this will allow easy attaching to the Prop Plug.

Start by disassembling the RSM, removing the 8 screws from the back of the torso shell. Gently pry the shell apart, taking care not to yank on the cable connecting the media board to the main board. Gently detach the connectors and the ribbon cables; the ribbon cables are held in by a small plastic bail that can be pried loose to release the cable.

Arrange the media board so the SD card slot is to your right, and the usb connector is to your left, with the processor side down. The serial port connections are a set of 6 solder pads to the left side of the board labelled J37, each pad is ~1 mm wide by ~3 mm long.

Media board

The top most pad (closest to edge of board) corresponds to pin 6 in Nocturnals pinout, this the ground (VSS; my green wire). Pin 1 corresponds to the pad closest to you, this is VDD (3.3V) but not needed for this connection. Pin 2 is the RSM's Rx, which needs to be wired to the Prop Plug Tx (my yellow wire); and Pin 3 is the RSMs Tx which goes to the Prop Plug Rx (my red wire). Here's how I laid out my connections, using 3 stranded wire:

layout

And here's the other end of the cable soldered to the pads, and in place behind RSM's head. (yes, I actually soldered with the board in place; it is tight but doable if you are careful!). Double check your soldering and wire positions before connecting anything, lest the magic smoke escape!

Now it's time to configure your communication program. I'm using HyperTerminal on WinXP, so you'll have to alter these instructions for your system. First, figure out what COM port your USB adaptor is on. Open the Device Manager and expand the Ports (COM and LPT) node:

Mine is on COM7, so now fire up HyperTerminal and create a new connection. Under the 'Connect Using' picker, choose your USB com port, then hit Configure:

Set your port as shown above- 115200 baud, 8 bits, No parity, 1 Stop, Flow Control None.

Now for the moment of truth: Connect your cables to the RSM and open the connection in your terminal program. While watching your terminal, turn RSM on. You should immediately see the Linux boot sequence, it starts like this (I cropped the image after capturing a screenshot):

If you see similar text appearing on your screen, congratulations! You can now explore the inner workings of your RSM!

If your screen is blank, it is time for some troubleshooting. First- tap a few keys in your terminal window while looking at the Prop Plug- you should see a blue LED flash for every character. If you don't see anything, you first need to check that your terminal program is talking to the correct port that the Prop Plug is on.

If your Plug is OK and flashing, then double check all of your wiring- no shorts, all wires going to the proper places? Try booting the RSM again, and watch for a red LED flashing on the Prop Plug- this is the data coming from the RSM. If you see the red flashing but still don't have any text appearing on your terminal screen, double check the communication parameters.

If after all that, you are still having trouble, just drop a line on the forums and ask for help- we'll pitch in and get you up and running!

Also, check out Nocturnal's article on C Programming for the RS Media! 

Comments

Rudolph's picture

Yay! I'm finally going to get to try this out. Getting one of these. Not wireless, but should be entertaining just the same. I just have to wait until christmas to actually get my hands on it...

TikaC's picture

Questions:

1. Is the prop plug, when used in this type of application, hot-pluggable? Or should we plug in the USB to the PC and THEN boot up the robot?

2. What guage wire did you use? Is the stuff that is used in PC Power supply hookups ok? I have a LOT of that wire somewhere...

3. Any suggestions on mounting this on the RS Media itself like maybe above the regular USB Port? It looks like it's mountable but plug up and not plug forward.

Nocturnal's picture

It should be hot-plugable. The current flowing is minimal, so heavy gauge wiring is not required, you can use heavy gauge wire, but you may run into trouble when trying to route it around. Think ribbon cable (floppy / ide).

I don't believe milw mounted it externally, I think he removed the panel behind the neck (above the media board), and left the cable loose. There are several other places you could run the cabling out, but if you have your heart set on mounting it, you could try something like this.

Though my choice of position only works if you remove the covering panels, which I had removed long before doing this (they tend to fall off when you remove the media board, and I got sick of putting them back).

TikaC's picture

Oh, well, I had the idea to put the Prop Plug right inside RS Media with the USB connector sticking out like that. Then use the included cable to plug into the RS Media and the PC. I rather prefer it that way. That is, if I can get it to fit. I don't want a situation where I have to have the robot partly disassembled, actually.

So what gauge wire should I use? So I can order some more wire if needed.

some1l8's picture

 

 Can this one do the job? I can't find any 'Prop Plug' in the UK. There's no VSS on the board which pin can be used instead? If it's GND, how to choose 3.3v?

nomad's picture

hi,there is there someone who nows ,how to get elmosapien out of my rs and,

put bugs bunny in.i don,t now how to do.thanks

FreddyA's picture

Nomad, take a peek at the table of contents in the manual. http://www.robocommunity.com/download/15549/WowWee-RS-Media-User-Manual/
basically you have to use the RS Media suite from wowwee, Santa Matts RS Media Editor or do it manually by deleting and adding personality files to the robot memory or SD card if you use one. Also, try a a search for rs media personality.

This thread is for and about a more advanced connection not related to connecting to USB mode for personality or media adding / deleting.

Freddy

gerber's picture

Please can someone help

I have just installed the serial hack and when I link to the robot through teraterm I get a load of weird characters when ever the robot does something or I press a button on the RS media remote control as you can see in the screenshot below:

If I use the mini USB connector on the RS media teraterm works fine.

Below is a screen shot of my device manager if this is of help

I am using windows 7 32bit and the same Serial hack module as  @Some118 which @jamie told me to order.(below is the picture of the device)

Please help?

Cheers

Gerber

TikaC's picture

First, are you certain things are soldered in properly? That's the first thing I'd check. Also the settings for this in TerraTerm might need to be different than what you use for the USB driver version. Make sure the USB console driver from the dev kit is NOT running in the robot at the same time you're using the serial hack. That might also cause conflicts.

The USB driver may be running at a different baud rate than the Serial hack. So if you are sure things are soldered in right, then try a different baud rate and experiment with the bit, parity, etc. as well. Something's gotta work. :)

Mike Row's picture

Where is the tutorial for the bluetooth?
id rather use a wireless connection, unless there is any drawbacks to it?
Nocturnals website is down, it seems.
Any help is much apreciated.

Michael Walsh's picture

Are there any drivers required for the prop plug? I would also requie hyper terminal, where can I get it and is it compatable with win7. Also does anyone have a copy of Nocturnals tutorial, I can't seem to get onto his website.

Thanks
Mike

Tareq's picture

I did the above .
Is there a way to develop program using windows xp ?
What is the commands for all motors using c or java?