Let's Make Robots!

microcontroller choice

i have  a problem: i only have on uc, an arduino, and have to build a tx unit with some cheap ebay radio modules. does anyone have any suggestions as to a small microcontroller for this unit. it only needs 2 or 3 channels.

 

i was thinking about a picaxe 08m. it has 3 analog inputs, so 3 channels wouldn't be a problem. i could also obtain a 3rd channel using this 555 adc circuit, or this guide, making full use of the circuit.(i was inaccurate)

 

Anyone have better ideas?

thank you

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In the fourth edition of RS Components magazine there is a test of an in-the-cloud ARM microprocessor compiler.

There are also other nice informations in the magazine. Check it out.

http://dk.rs-online.com/web/generalDisplay.html?id=eTech&cm_mmc=short_url-_-June_10-_-eTech-_-eTech 

nice, but perhaps a little too powerful for a simple 2 analog signal/channel tx

I just looked up the 555 circuit you are stuck on. Did you read ANYTHING before asking your question!? The 555 circuit does not work with an input voltage below 5v... You shit on my head with my simple idea of "use a bigger fucking chip" and instead want to:

Use a 08m

Build an entire external circuit for an extra ADC channel you don't need. --Or-- build a RC timer circut, that the picaxe can't read and uses 2 pins, not one.

Build an external power supply so your 555 circuit will work.

Why the hell did I waste an hour of my life trying to convince you to "use a bigger fucking chip"?!?!

Man, this one got to me tonight.

 

First of all, i would like to apologize for not having done my research properly. I thought that the 08m had 3 inputs and only 2 could be used as analog in, and 1 was only digital in, or at least this is what i had heard and been told when i previously posed the same question. Hence, if i wanted a 3rd adc i needed some external analog to digital external converter, or at least i though so.

As far as the some knowledge i meant someone with experience, as someone who had built a 3 channel transmitter with an 08m, and far as i see, you were the closest, as you had built a small 2 channel transmitter embedded in a wii nunchuck, with an 08m(here). Unless i am really not processing things the correct way, you had also used a 08m with a cheap ebay radio module.

I did check the 555 circuit: it uses a 5 volt vin.

i can replace that with a 3 volt vin, and have it read analog values from 3 volts up. with a couple of diodes i stuck the pot between 3v6 and 5v, and took those analog readings, and it works. i have tested this circuit before posting it, i'm sorry i forgot to specify this, hope i remember to next time.

once again i am sorry for my inappropriate conduct.

Yeah, I had some similar experiences, but I gave up before I got pissed like you did. Some people just don't get it. You give them links with stuff that needs to be read and they save it for later and keep bugging you. Oh well, at least most people are thankful and learn something. 

Hey, Chris. At least you entertained some of us with your rant! ; j

I started this conversation assuming you had checked the data sheet and that you aware of the number of ADC pins on the 08m. We then spent an hour discussing options via the shoutbox. During that discussing you said you wanted to control the robot via the computer and would need a rs232/ttl converter. Then you said you were lazy and didn't like to send data back-and-forth to the computer. We eventually got to the fact that you wanted to make a simple hand-held remote and you told me that you didn't have the adc pins you needed. Again, I assumed this whole time that you had done some research before asking your question so I did not question the fact that you were short one ADC pin.

After about an hour of going back and forth, I finally went and RTFM and quickly found that yes, you have all the pins you need. At that moment, I found that I had wasted 1 hour of my life discussing a problem that did not exist --An hour I would not have wasted if you had done a tiny bit of research before asking your question. You have been around long enough to know better.

After this, the conversation ended with: "pips17: i'll just see if anyone with some knowledge answers the post". Really? Really? I gotta tell you, you can be sure I won't make the mistake of trying to help you again.

Let's go over the facts:

You didn't look up a God Damn thing before asking your question. You (based on the "someone with knowledge" comment) were pissed at me because I didn't look up the pin-out and assumed you did.

You thought you didn't have enough pins and are stuck on using a RC decay timer on a 555 circuit to add a ADC channel. --This makes no sense at all. A 08m costs $4, a 555 is around $2 plus all the parts you will have to add to build your 555 circuit. Now we are in the $7 or $8 range with is what you would spend on a 28x1 or 28x2. You are spending the same amount of money here for either option so why would you want to go through all the bull shit of building a circuit, testing it, stuffing this second chip into your transmitter case, etc. etc. etc. Instead, AS I SUGGESTED IN THE FIRST PLACE, just upgrade to a bigger chip FOR THE SAME AMOUNT OF MONEY and just use the ADC as it was intended. Not to mention, if you are an arduino guy and are switching to picaxe for this project, you will be testing a new circuit (the 555 thing) at the same time you will be learning code --why would you double up on things that can go wrong? Simple is better.

Now, if you are curious about measuring analog values using the RC method, fine. I think it is cool too and understand that you would want to experiment with it. But in terms of the question you have asked, this is irelavent. It is not needed, complicated and will slow you down in terms of getting this particular project done. But then again, you may want to find someone with "knowledge" to confirm this.

The bottom line is, you knew what answer you wanted before you asked for advice. During our conversation, I was not giving advice, I was wasting an hour of my life while you tried to convince me that the answer you had already decided on was the right one. So do whatever the hell you want. Make you RC/555 circuit and play to your heart's content. Wire your TX unit to a 08m, an Arduino or your asshole for all I care, when you discover that you have no way of timing with the 08m using the RC method of reading analog values, don't call me. When you discover that 256 bytes of program space doesn't go very far at all and your program won't fit --don't call me. When you find you need 9600 baud and you have to over-clock to get it and all your pauses are weird, don't call me. When you find that you wasted $4 on a 08m and should have spent $8 on a chip that is many, many times the size, twice as fast with a shitload more program space --don't call me. When you fill-up every pin of the 08m, want to upgrade in the future, and only then find you should have bought a bigger chip in the first place, don't call me. Call someone who has actually worked with all these chips, read the data sheets and has "some knowledge" on the subject. You have lost my help.

Good luck.


Computer --> USB/FTDI --> Picaxe 28x2 --> TX unit. Your joystick and other input devices also go to the picaxe chip. Now you can go any direction you want... Joystick to TX, Computer to TX, Joystick to Computer and Computer to Picaxe. This set-up will allow you to do the tweaks you need to do to get the cheap TX unit to work via the picaxe, not the computer so it will be much easier.

There is just a 3 or 4 dollar difference between the 08m and a 28x2 (about the same you would spend to build and add your 555 circuit) so I see no reason at all to do this with a 08m. Also, the 08m runs a 4mhz so you will have to over-clock it to get up to any reasonable baudrate (I am not sure a 08m can do this). From there, just find frits's post on getting these TX units to work and you will be all set.

 

using this guide: http://letsmakerobots.com/node/13843 would work without the need for a 555. that leaves 1 free digital out pin, which makes full use of the 08m, so i can have a small handmade joystick for all projects.

They can. I do. So they can drive an RF link @ 4800 b/s.