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1  Using Arduino / LEDs and Multiplexing / Re: Problem with CD74HC* Multiplexer/Demultiplexer on: July 09, 2014, 10:04:19 am
Any idea why this happens and/or how to fix this?
It sounds to me like you have not connected all the multiplexer pins to something and some of them are floating.

yes some of the pins are floating, but only the ones that are neither sending information nor being read.
Do those need to be connected as well? I'll test that out today and report back to those of you that are on pins and needles waiting to find out if this works.

pun intended
2  Using Arduino / LEDs and Multiplexing / Re: Problem with CD74HC* Multiplexer/Demultiplexer on: July 09, 2014, 09:55:06 am
Are you saying if you select an input (which is high) then select another input (which is low) the pin on the controller is always high?

Yes but only AFTER I've read the High input

So if the output I'm reading is


The input I read is

3  Using Arduino / LEDs and Multiplexing / Problem with CD74HC* Multiplexer/Demultiplexer on: July 09, 2014, 12:14:46 am
I am testing a communication scheme whereby an arduino communicates with 12 others through a network of multiplexers. By cycling through the demultiplexers much faster than the multiplexers, I hope to establish communication between connected nodes by putting one channel on HIGH on the multiplexer, then reading this out on the connected demultiplexer.

(The reason why I am doing this, as opposed to using a shift register, is that these pins can then double as TX and RX for serial communication between the arduinos. If you have any advice for performing serial communication over a shift register, I would be incredibly happy.)

To test this scheme, I have two arduinos connected through the Multiplexer/Demultiplexer pair (broken out in this way The multiplexer's com is connected to Digital Pin 10 which is high and routed so that four of the pins look like this.

On the other side, the demultiplexer is connected to Pin 11 and set as an input pin. It then cycles through each of the inputs on the demux, and reads the value. However, it seems like once the input pin is pulled to high, it stays high. Thus for the given input configuration, the output configuration is:

Any idea why this happens and/or how to fix this?
4  Using Arduino / Networking, Protocols, and Devices / Serial Broadcast Communication with Bluetooth on: December 17, 2013, 05:38:27 pm
I am seeking to simultaneously send the same string over serial from my computer to multiple arduino components connected to the computer via bluetooth. I am using the bluetooth mate gold from sparkfun and arduino pro minis.

The string will have instructions for each arduino in the format "{ID  #1}: {Parameters} | {ID #2}: {Parameters} | ..." The Arduino will parse the string, pick out the parameters that correspond to its ID, and use those parameters in its program.

is this the best way to do things? i am seeking for the commands to be parsed (relatively) at the same time, so I am thinking that this is the most effective way to simultaneously talk to 3 different bluetooth connected devices. However, I have no clue how to do the broadcasting. Right now, each bluetooth connects to my computer via an individual COM port, and I have no how to set up a port that sends the message to all three bluetooth devices at the same time.

Thanks alot for reading this! Any help is greatly appreciated.

Alternatively, If I could send the command from a fourth Arduino (a Mega) to the other three, that would be even better.

mate gold:
arduino pro mini:
5  Using Arduino / Audio / rMp3 Spectrum Analysis Issue on: December 22, 2012, 04:32:20 pm
I've been working with the rMp3 shield from Rogue Robotics for most of the day, and I'm pulling my hair out over one thing. I'm running the example code located here:
However, I don't have an LCD so I am instead routing the output values from the spectrum analysis array to a line that says
and looking at the resulting intensities over time.

Other than this print command, I have made only one other change to the code. I cannot get it to run with a baud rate of 38400, so I had to run
at 9600. If I change the serial rate to anything other than 9600, the shield will not sync, and so I can't even play the music.

Logically, I should see the decibels that are associated with each of the frequencies, right? Instead, I get nothing that's even slightly associated with the values. I do get values and they do change, every once in a while.

Is this the right way to look at the simple output of the system? How important is the baud rate for this? How do I get it running for a baud rate higher than 9600? I'm just looking for the values to change if the music changes, and I'm not even getting that.

Thank you,

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