This is the fourth part of several posts. I will be explaining about how I connected my phone to Arduino via Bluetooth.
Links:
Part 1: Initial Plan and Reverse-Engineering
Part 2: Preparing the Rover Chassis
Part 3: Motor Control
Part 4: Bluetooth!
Part 5: Mounting
Part 6: Batteries
Part 7: The Test
The rover was coming along nicely, however I still couldn't control it remotely. Options for communications were:
A. WiFi: Hosting a webpage on the rover, and inputting commands from a computer or phone. Advantages: Higher bandwidth, range while in free WiFi. Disadvantages: would only work in free WiFi, and would require a special "shield" that goes on top of Arduino.
B. Bluetooth: Connecting via phone and driving with an interface. Advantages: Works without WiFi, doesn't require special shield, uses Arduino's built in serial capabilities for bit-by-bit communication. Disadvantages: Lower bandwidth than WiFi, lower range while in free WiFi zone.
Let's compare:
WiFi
Bluetooth
Bandwith
Flexibility
Control quality
Weight and size
Cost
Cool factor (0.25 points)
Sorry, WiFi, but I think Bluetooth wins 4.25 to 1.
This means that a continuous video feed is not really an option. The highest serial 'baud' that Arduino can muster is 115200. If I was to try to send a 640 by 480 pixel video feed of 10 frames per second (using grayscale instead of color), that would be 640 * 480 * 10 = 3,072,000 necessary bytes per second. That's about 3 megabytes per second, 26.66 times what is available. Kind of disappointing. On the bright side, I'll still be able to press a button on my phone and receive a single picture... over the course of 2.66 seconds.
I looked online to see how people usually do Bluetooth connections with their Arduino and discovered that the most popular Bluetooth module was the HC-06. After some research, I discovered that it was capable of using a higher baud rate than Arduino could handle, but had a lower default. It also ran on the standard 5V that Arduino outputs... Not bad. There were also guides everywhere, so the HC-06 it was.
It's $9.49 on Amazon with free 2 day shipping (Amazon Prime only). When I got mine, I think there was a 50% sale.
While waiting for it to come in the mail, I had to slap together some Android code. I downloaded this guy's example and set about reverse-engineering it. There was a disturbing number of references to Chihuahuas. I've been working on my own app for a while, so all I had to focus on was the Bluetooth code. Please note that the project folder is formatted for Eclipse. I had to manually copy the source code into Android Studio (I only took part of it).
Modifying the code was a big task (Android code terminology ahead!). The first thing I did was delete the Chihuahuas. Then I ditched the layout and created my own (one that will be easier if I'm looking at the rover rather than my phone). I changed the search term for the paired devices from "HC-05" to "HC-06". Then I set up the controls to broadcast a single-byte command every quarter of a second depending on which buttons were pressed, rather than as the buttons were pressed. I added another activity for pre-driving setup (custom search term, more stuff to be added later). I also worked on cleaning up and custom-formatting the code.
Then there was the Arduino code to design. A quick Google search revealed that it's as simple as making a SoftwareSerial on the proper pins. I didn't bother downloading anything for it. The complete code sends a message through the HardwareSerial to my computer every time it receives a command.
On the day of projected arrival, I discovered that the relays had come early, and didn't notice the big yellow bubble-protected envelope containing the HC-06 (facepalm). I realized my mistake in the late afternoon...
On the hardware side of things, it's pretty simple to set up.
Here's where the pins go:
GND --> Arduino's GND
VCC --> Arduino's +5V
RXD --> Voltage Divider to TX on Arduino (More on this in next paragraph)
TXD --> RX on Arduino (Don't send these to the 0 or 1 pins. These are used to communicate with the computer)
After doing my research, I noticed that some people skipped the voltage divider, and some people regard it as necessary. Both groups say that it works for them, but the RXD pin is technically not supposed to be exposed to the full 5V of Arduino's pins. Here's a link to the page I learned most about how to do it.
Looking into my inventory, I don't have any 20KΩ resistors. That's ok. I'll just use two 10KΩ resistors in series.
Plugging everything in and verifying hardware connections... No bluetooth connection. More troubleshooting:
Switching RX and TX pins: Nope.
Staring at it to use the Force: Why??
Checking on Bluetooth menu in phone settings: Getting somewhere. It sees the HC-06.
Tapping on it and inputting the default password (1234): Bingo! Now the phone and Arduino are "paired" together!
Trying again: It works! Every quarter of a second while pressing a button on my phone, Arduino sent a message of "Received right command" or "Received forward command"!
I wonder why the Chihuahua code didn't automatically pair with the device... Probably doesn't want to accidentally pair with random devices (smart).
I think I'll wait to post downloads of my own code until the post where the rover is driving successfully (Sure, I'll do it sooner if the comments ask me to). I encourage anyone wanting to, to try and make their own code. I only downloaded the Chihuahua code to figure out how to create and maintain a bluetooth connection (I'd been struggling). Anyone with the same problem can go ahead and get the Chihuahua code. The Arduino code is so simple it shouldn't be necessary to download.
Edit: 7/8/16: Updated list of links
Edit: 8/25/16: Updated list of links
Edit: 7/6/17: Updated list of links
Then there was the Arduino code to design. A quick Google search revealed that it's as simple as making a SoftwareSerial on the proper pins. I didn't bother downloading anything for it. The complete code sends a message through the HardwareSerial to my computer every time it receives a command.
On the day of projected arrival, I discovered that the relays had come early, and didn't notice the big yellow bubble-protected envelope containing the HC-06 (facepalm). I realized my mistake in the late afternoon...
On the hardware side of things, it's pretty simple to set up.
Here's where the pins go:
GND --> Arduino's GND
VCC --> Arduino's +5V
RXD --> Voltage Divider to TX on Arduino (More on this in next paragraph)
TXD --> RX on Arduino (Don't send these to the 0 or 1 pins. These are used to communicate with the computer)
After doing my research, I noticed that some people skipped the voltage divider, and some people regard it as necessary. Both groups say that it works for them, but the RXD pin is technically not supposed to be exposed to the full 5V of Arduino's pins. Here's a link to the page I learned most about how to do it.
Looking into my inventory, I don't have any 20KΩ resistors. That's ok. I'll just use two 10KΩ resistors in series.
Plugging everything in and verifying hardware connections... No bluetooth connection. More troubleshooting:
Switching RX and TX pins: Nope.
Staring at it to use the Force: Why??
Checking on Bluetooth menu in phone settings: Getting somewhere. It sees the HC-06.
Tapping on it and inputting the default password (1234): Bingo! Now the phone and Arduino are "paired" together!
Trying again: It works! Every quarter of a second while pressing a button on my phone, Arduino sent a message of "Received right command" or "Received forward command"!
I wonder why the Chihuahua code didn't automatically pair with the device... Probably doesn't want to accidentally pair with random devices (smart).
I think I'll wait to post downloads of my own code until the post where the rover is driving successfully (Sure, I'll do it sooner if the comments ask me to). I encourage anyone wanting to, to try and make their own code. I only downloaded the Chihuahua code to figure out how to create and maintain a bluetooth connection (I'd been struggling). Anyone with the same problem can go ahead and get the Chihuahua code. The Arduino code is so simple it shouldn't be necessary to download.
Part 5 will be about my search for ways to mount my Arduino to the rover.
Tips jar is for you, not me!:
1. Be conservative. It wouldn't have been very fun to kill the bluetooth module via overvoltage.
2. Do it yourself (if you can). It's very important to learn what's going on under the hood, and the best way to do that is to make it yourself. If you're stuck, you can get some help, but still do your best to understand.
3. Don't give up troubleshooting!
Edit: 8/25/16: Updated list of links
Edit: 7/6/17: Updated list of links
Enjoyable read.
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