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I’m in the process of creating a robot that requires a IR/RF link to control. I’m somewhat of a beginner at programming (second year of engineering).
I am going to use one MC for the robot and another for the controller (which I would like to interface to a computer using a DB9).

What is the easier method of control (IR/RF)?
What microcontroller is the best for that method?

Greetings (No Name supplied),

OMEN4 wrote:What is the easier method of control (IR/RF)?
What microcontroller is the best for that method?

RF is much easier as IR signals are very directional,
something you may have noticed with an IR remote
for your TV, etc.

RF modulesmake the hardware very easy. It's just a
module you power up and feed data into at the TX,
and a second module (RX) spits back the same data
at the other end. You can even run two paths (duplex)
if the two RF signals are on separate frequencies.

As for the uC, the simple answer is to use what you
are familiar with, or what is available to you.

The Nuts and Volts magazine features a lot of Microchip's
PIC family, but others use Atmel's AVR devices,
both have their place, this articleshould help.

More specialized applications use ARM based
processors from other vendors.

Many robitics projects are constructed around the
Basic Stamps and the popular Arduino board.

Comments Welcome!

I haven't used these yet, but Cypress Semiconductor is quite happy to give free samples of their "WirelessUSB" modules to students. (Not to be confused with "Wireless _ USB" - Cypress's is proprietary). They have a double-row header on the bottom, a built in antenna, are really small, and communicate by SPI, which is about the simplest protocol you're going to get.

As for an MCU, I don't have a lot of experience with any of them, but if you know C, you could also order an AVR from Atmel. They didn't respond to the samples form, but when I e-mailed and asked nicely, they said they'd send some free too. The Arduino is actually an AVR with a bootloader installed - which is open source; if you get an appropriate AVR, you could turn it into an Arduino if you wanted anyways. (This probably isn't the most cost-effective way to do it, but it's an option).
Make sure to look into programmer options before you buy one. One of the common Parallel port ones for the AVR is sold for as much as $26CAD, but is this simple, and could be built for a lot less. The PICmicro programmers can be more expensive, although there are DIY ones too. The Basic Stamp and Arduino don't even need one
Also, make sure that you can get a reasonably-priced compiler for the MCU you choose. To my knowledge, PICmicros' C and BASIC compilers are all very expensive. AVRs have a free, very good compiler based on the Linux GCC - just look up WinAVR for the Windows version. The Basic Stamp and Arduino both have free compilers too.

Sorry for the long post. I'll call it "comprehensive", so it sounds good

during my time at motorola , i worked extensively with R-NET rf telemetry modems. they worked well. they were even used on the mars rover.

Greetings (No Name Supplied),

jaem wrote:Sorry for the long post. I'll call it "comprehensive", so it sounds good ;)

Did you have a chance to read the article that I cited?
Was it helpful?

Comments Welcome!

I would recommend the Picaxe family of micros. Chips have built in radio and infrared xmit /receive capabilities. All programming software is free and doesn't require a compliler. Here's the link for all you need to get started.
http://www.rev-ed.co.uk/picaxe/

Steve G.

Thanks for all the input. I just got word that I have to use a Rabbit 2000 for the MC. SO... I have decided to go with this AM transciever for the connection:

http://www.abacomdirect.com/AM-RF-Trans ... 23628.aspx

I think the connection would go like this:

MC----->UART----->TX In

Or is there a more efficient way to hook it up?

Greetings (No Name Supplied),

OMEN4 wrote:I think the connection would go like this:

MC----->UART----->TX In

Or is there a more efficient way to hook it up?

That's about it, assuming that the USART is a uC
hardware type. If it's a software UART you can
skip it and use any port pin for serial data.
This radio link would use OOK modulationof
the AM RF carrier.

However, the radio will not 'transmit' DC so the
data has to be some format with many transistions.
(You can't send &HFF or &H00 for example as the
TX will see this as a DC level, and the receiver
will not output the same data as the TX input.

One way to scramble the data is to encode a
clock so that the &HFF string becomes &HAA or
&H55, etc. A suitable encoder method is called NRZ.
Manchester Encoding is another popular technique.

On the receive side their will always be a recovered
clock even if the data is unchanging.

The same vendor sells encoder ICs for this job,
or the encoding can be done inside the uC code.

Comments Welcome!

Bigglez wrote:Greetings (No Name Supplied),

jaem wrote:Sorry for the long post. I'll call it "comprehensive", so it sounds good

Did you have a chance to read the article that I cited?
Was it helpful?
Comments Welcome!

yes, thanks - I think what happened was that I went to that link and got sidetracked for a while... then came back to write my post and forgot about what I had originally gone to that site for... sorry for going on unnecessarily

Greetings (No Name Supplied),

jaem wrote:yes, thanks - I think what happened was that I went to that link and got sidetracked for a while...

I think we've all done that at least once! I asked as
I wasn't sure if the link was useful, the last thing I'd
want to see is a PIC vs AVR vs ARM war, as they each
have a place.

Comments Welcome!

Fair enough... I have a tub full of PICmicros, but I'm putting them on hold until I get better at ASM, or someone releases a Free/Open Source C compiler for them. The GCC target for AVR is a very nice thing, whatever the merits of the MCUs themselves. I'm hoping I can twist the arm of some comp-sci student at my university to retarget GCC for the PICmicro - I don't have the skill.

Jeam, that is what makes the Picaxe easy to use, programming in Basic is easy and comes natural, at least to me. Also, they are Zigbee 2.4GHz ready at very reasonable prices with the transciever boards already populated and ready to go.

Digi/Maxstream XBee series 1 are plug and play 802.15.4 modules. Low cost.
Free firmware for wireless serial port extension.

Series 2 are ZigBee oriented; use ZigBee only if you need the complexities of mesh routing. Series 1 allow A to communicate with B, and A with C and B with C, etc. Point to point, using the radio's MAC address.

why not use a PICAXE

It is a good help for beginner.