Let's Make Robots!

Building a Universal RF Remote - Questions

More Recent UPDATE: the competed remote can be found here. Thanks to fritsl and rik for their respective helpfulness.

UPDATE: Attached (and blurrily pictured below) is my schematic that i think will work for this remote. Yes I drew it in paint, Yes it took too long:

*The "To Breadboard" leads are included so that the remote may also serve as a portable power supply.




Can an RF transmitter like THIS and its corresponding reciever communicate with more than one command at a time? What I mean is, if i press two buttons on a remote will both commands be able to be sent to the reciever?

(Thoughts to myself: Is this a matter of whether it can send two or more commands at once, or whether I can program to cover the combinations of buttons pressed and compile the desired outcome of pressing two (or more) buttons into one serial message sent over RF... which i guess is possible.) This will be my first robotics related project undertaken without a step by step guide, but I still need a little help :)


The reason i ask this question is because the answer dictates how i construct the remote. As seen below is an IR remote that is not dissimilar to what i'm thinking. However, its button layout is momentary push buttons in series, in parallel to resistors in series, connected to an analogue input. That is, when a button is pressed, the analogue input gets fed with a specific resistance value for each button and so does what you tell it to when it gets that reading. The problem with this however is that only ONE button may be pressed at a time (in most cases, you can press two but only one will be active because it short circuits the second one.) If RF does not support multiple RF commands, then i would simply wire the remote in a similar fashion to this one, as it is simpler.

 If however, RF can support multiple commands then I can dedicate one digital input to each button, and two analogue inputs to each joystick (two of them). This will, however, create a lot of connections to be made between two protoboards that are going to be stacked with small spacers (like in http://www.inklesspress.com/picaxe_projects.htm , second project down.)


The number of I/O pins available is not an issue, as i plan to use a PICAXE 28X2 (for educational reasons i thought it would be a good idea to expand my experience to the X2 range at some point.)


Other details about my project.

Signal: RF Link Transmitter - 315MHz

2 x Analogue joysticks and up to 10 momentary push buttons

Mode select button to allow multiple uses of each button (this is universal, i have to keep the future in the scope of the project)

powered by a single AA or AAA cell, by using a Pololu 5V Boost Regulator NCP1402

connections between the two boards will be made using break away male headers soldered to one board, mating with break away female headers soldered to the second board.

remote.JPG61.95 KB

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Now that rik mentioned the problem of reading multiple keys I remembered this link: http://www.user.dccnet.com/wrigter/picaxe/08M%20sea%20of%20keys%20and%20touchpad%20encoder.htm

There's an implementation of "sea of keys" (127 keys) done with 08M. You might find that useful. I haven't tried that myself. I just ran into it when I was looking for material about tri-stating.


Well as far as i know TVs only accept one single command at a time. Trying to send more then one at the same time would probably send a screwed up command (a mix of the two) that TV won't understand. So if the TV is what you are trying to communicate with, i'd say just go with a command at a time. This also applies to the RF module. (...and you would need two MCUs to send two commands at a time)