analogarduinobluetoothh-bridgeserial
Simply put I have the following:
With a
Plugged into it
Now the last part needed is to hook up my
so I can control the Motor Drive shield.
Here's the problem though, the Motor shield uses
EVERY SINGLE DIGITAL PIN ON THE ARDUINO!
I have
5 analog pins
open though.
Am I able to turn analog pins into TX and RX for the bluetooth??
So this is just a bare board with a few LEDs and buttons. jippie points out that series resistors are indeed included, as can be seen in the picture he linked to. (Thanks jippie.) The buttons don't have pull-up resistors so they seem to rely on the AVR's internal pull-ups for that.
A schematic of the board would help. I would find it hard to believe there wasn't one included, or at least a link to the schematic on their site. On the top side LEDs and buttons don't seem to be connected to anything, so we need to have a close look at the bottom side. Can you post a sharp picture of that?
It's unlikely that LEDs or buttons would be hard-wired to any of the I/Os, but the bottom row of the breadboarding area is possible. I marked two intriguing holes next to LED2. They're not vias, but more like the holes on the breadboarding area. They seem to suggest connections for the LED, but then where are the connections for the buttons? So I'd go back to the breadboarding area. Check if you see traces connecting to the holes on the bottom row.
Once the connections are cleared up you'll have to wire up the LEDs from +5 V to a digital output of the controller. Making that output on the Arduino low will light the LED.
The button goes between a digital input and ground. You can use the microcontroller's internal pull-up resistors, or use an external one. This goes form the input to +5 V. If the button isn't pressed the resistor pulls the input to +5 V, so you'll read a 1. When you press the button you connect that input to ground, so that will read as a 0. You can use a 10 kΩ for the pull-up.
I just checked the datasheet for the L298P, which is used on the shield. It's a bipolar based driver, and has a typical saturation voltage at 1A of 1.35V source and 1.2V sink, so a total of 2.55V. There is also a total drop spec given at this current of between 1.8V min and 3.2V max (see page 3 towards the bottom)
8.5V - 5.8V = 2.7V, so it seems what you are seeing is about right.
Here's a thread which discusses the drop, mentioning 2.6V.
So you need to raise the voltage to allow for the drop, but be careful of dissipation at higher currents. The higher the drop, the higher the power dissipated - there looks to be no heatsink on the chip judging from the picture, and I don't know whether they put a solid plane underneath it, so be careful not to exceed the maximum temperature (the datasheet has thermal resistance and max junction temp)
There are MOSFET based ICs out there which will not have this kind of drop (random example is the L6203), so you may want to consider buying a shield that uses one of those (or if there aren't any, making your own based on the chip)
Best Answer
The short answer is yes. The only part of the "analog" pin that makes it analog is that if you want you can use them as inputs to the internal ADC. That said you can use them like any regular I/O. The tricky part here is that you won't have the ability to use hardware serial port (since you say that the motor driver takes all the other pins). Therefore you'll need to implement this in software. I believe there's already an arduino library called "software serial" so 99% of the work is done. You'll have to double check that the bluetooth module uses a uart interface. It looks like it's 9600 bps so that shouldn't be hard to handle in software. Check start/stop bits etc. Ultimately you'll have to see if your software loop can keep up with both the motor driver and the radio. This will depend of course on how much data you're sending/receiving and how often you're servicing the motor driver. You should probably be OK.