Pi Power -- How I Made a Battery Powered USB Hub

Originally posted on www.letsmakerobots.com

As I prepare to start adding peripherals to my Pi Bot, I wanted to be sure to get around the 700ma power budget the Pi has. After searching for a cheap battery powered USB hub and finding little, I decided to hack up a few cheap(ish) parts and make my own.

  1. USB Hub: $1.39

  2. 5000mAh Battery: $17.93

  3. DC-DC Converter: $2.76

Total: $22.08

The Battery Hack:

1. Crack it open.

2. Find POWER and GND.

3. Wire it up.

4. Make a small hole for wires and bring wires out.

5. Solder the respective leads to the DC-DC converter.

6. Smile, then sit through my way too long of a video to make it into the HUB.

Hope all are well. :)

NOTE: Regarding the error at the end of the video. Don’t panic (that’s what I did). I actually found out this had nothing to do with my hub, it had to do with plugging an iPhone into a Raspberry Pi.

NOTE2: I realize I used the wrong “hearty,” my brain has problems typing homonyms and parahomonyms. :P

Blueberry Pi -- How I Setup My Raspberry Pi as a Robot Base

Originally posted on www.letsmakerobots.com

This article is specific:How I personally would setup my Raspberry Pi to act as robot base. But, I’ll be clear, this is one of nth possible setups. A chessboard has 64 squares but those working the board allow for innumerable possibilities.

That aside, here we go:

1. Get Berryboot. Berryboot will allow you to download several Raspberry Pi images.

Now extract the zip files to a blank SD card.

Put the BerryBoot SD card in your Pi and boot it up.

2. Setup RPi with Raspbian Wheezy (first option).

3. Setup your WiFi dongle. I believe BerryBoot will now setup your WiFi dongle on initial boot, which it did for me (even gave me the option to download the image via WiFi). But, I had trouble getting my WiFi dongle pulled up after booting Raspbian Wheezy.

If you have difficulty with manual WiFi dongle setup, you might try this video.

Lastly, if you are looking for a WiFi dongle for cheap, with good range, and uses very little mAhs (the Pi can only feed about 700mAhs through the USB port). You might try this one, $6.17.

4. Setup PuTTY on your Desktop Computer. Follow this video.This will allow you to begin SSHing into the Pi. That way you don’t have to look at a little RCA screen like me. For those who aren’t familiar with SSH (like I was before this video), the video will explain it. At risk of oversimplification,it allows you to access your Raspberry Pi command line through your desktop.

You have to plug in your Pi’s network number.You can find this by pulling up your wireless hub’s configuration page. You should see what address your Pi is listed at. For some strange reason, if it doesn’t list the device name, just view the page while the Pi is up, then unplug your Pi and refresh the wireless hub configuration page. The device that disappeared is your Pi. I’ve never had to change the port number, but beware you might need to depending on your setup.**

If you want to know whether your have the correct information, try login’ in and if you get a screen like this, your good.

Your username and password are by default:pi, raspberry

Remember! In the case of a Raspberry Pi, always share your password, ‘cause everyone has it anyway :)

Once you have PuTTY setup, you should be able to bring up your Pi command line, something like this:

5. Setup VNCServer on your Raspberry Pi. Follow this video. (Or this walkthrough). Putty will let you access your Pi’s command line, but setting up a VNC will actually allow you to access your Pi’s Desktop GUI from your PC, in the same manner as Putty.

**6. Setup a VNC Client on your Desktop Computer. Real VNC. **There are many different programs, I happened to end up using Real VNC.

Once you have VNC setup on both machines, PuTTY into your Pi and start the VNC server.

$sudo vncserver

Two notes here, if you did better with the video instructions than I did, your vncserver will start automatically on boot. Unfortunately, I have to type it each time (I’m too lazy to figure out the boot part of it). As a result, you’ll have problems running certain Python scripts through VNC if you don’t use $sudo vncserver

You’ll enter your Pi address, but port should be 1 (if I remember the video instructions correctly).

You should end up with at a windowed version of your Raspberry Pi desktop. One more note, somewhere in the video it gets you to setup the “geometry” of the VNC desktop. The limitations you put there will be reflected in the quality of the desktop you see in the window. In essence, if you put in 640x480, that’s the resolution this desktop will end up. So, please, take advantage of the Pi’s GPU :)

Use something like this, “-geometry 1024x728 -depth 24”

7. Resize your SD card to use all its space. (Note, this should already be done by BerryBoot. But other diskimages will limit your SD card to 2GB, regardless of its actual size).

8. Git manager will allow you to pull code from git hubs (again, this should already be installed, but just in case).

I**nstall the git manager: **

At Raspberry Pi prompt: **$sudo apt-get install git**

The way to use it is like so,

At Raspberry Pi prompt: **$sudo git clone https://github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code.git**

9. **Install SMBus. **This is specifically for my setup, since I’ll be using the I2C bus to communicate between the Pi and the Arduino.

At Raspberry Pi prompt: **$sudo apt-get install python-smbus**

10. Any other Python modules you might fancy.

Useful for keystroke, GUI, and other interfacing needs:

Pygame (should come with Raspbian). (sudo apt-get install pygame)

Lady Ada’s Python codes for an array of I2C sensors:

Adafruit I2C library (git)

Access your Raspberry Pi from iDevice web based GUI:

PiUi (git)

Control serial devices:

pySerial (sudo apt-get install python3-pyserial)

(I’ll add other resources as fellow LMRs leave them in the comments).

11. (optional) Install Arduino IDE on Raspberry Pi. This will allow you to program the Arduino directly from your Pi–and if you follow my design, you’ll be able to do so without ever leaving your desktop computer. You can do this by opening the VNC Server, opening the Arduino IDE on the remote desktop, selecting the sketch you want to upload, and as long as your Arduino is connecting by way of USB, you can then upload your sketch from where you sit. This allows for quick changes to Arduino code without switching wires around. Also, I think Kariloy is looking for a way to upload sketches by way of GPIO pins. This would make a cleaner design.

**12. Install WinSCP. This will allow you to transfer files between your desktop and the Pi. **I find this helps with programming management. I’m a messy filer. If I file at all.

13. Take a deep breath.

14. Follow these instructions for making my I2C optoisolator board.

Again, there are many commercial boards that will serve the same function. Also, you can do the same with a USB cable, serial pins to GPIO, or RF connection–basically any way that lets the Arduino and Pi talk at a reasonable speed. The speed restraint will of course depend on your need. I doubt many methods will be apt for running a responsive quadrocopter. But in my case, my Pi is the central nervous system and the Arduino is the autonomous nervous system. The Pi will send directives, but it’s up to the Arduino to manifest them through responsive actuators. And I chose this optoisolator because I didn’t want an voltage restraint on my actuators or fear of frying my Pi.

Once you have the board setup, you can run:

$sudo i2cdetect -y -a 1

This should bring up a list of active I2C registers. You should find your Arduino at whatever address you set in your Arduino code.

Now, I’ve read this fellow’s article on how Raspberry Pi I2C pins are actually 5v tolerant. (Note, this is only for I2C pins, due to their pull-up resistors.)

So in theory, you can skip the optoisolator all together. But that’s you, I’ll stick with my optoisolation.

15. Download my code–or someone cooler’s.

Note, my code is really just the base for a robot. Right now, my it is nothing more than a very, very complex radio controller for a RC car. But someday, I’ll make a real robot :)

**16. Tweak and gut the code as you see fit. **

17. Ask questions: Pretty much everyone on this site is smarter than me, they’ll know the answer.

To other LMRians. Please feel free to tell me how to change, add, or retract from this article. As tired as I am right now, I plan to revise when I’m less muddled.

Arduino to RPi -- Galvanically Isolated I2C

Originally posted on www.letsmakerobots.com

Breakout PCB Arduino Code

I’ve waited to finish incorporating my Raspberry Pi into my bot for an ample bit. But since I know so little about electricity, I swore to myself I wouldn’t add my Pi to my bot until I was absolutely sure I wouldn’t fry it.

Well, I’m still not “absolutely” sure, but I feel this little optoisolator has brought me a lot closer. This builds on my post a week or so ago about making Eagle parts.

I plan to actually list out what tweaks a Wheezy image needs to get this optoisolator build to work. It’s actually pretty easy–but whatever you, don’t be lured in by quick2wire. Those buggers wasted most of my day :(

If anyone has questions let me know.

Oh, one note. When I populated the board I used 4.7k resistors on the Arduino side, but I pulled off everything on the Raspberry Pi side. It seems the Pi has built in pull-ups that do the job rather well.

ADUM1250ARZ Datasheet

Hope everyone is well :)

Populating and Programming and APM

Originally posted on www.letsmakerobots.com

I decided to try making an Arduino Pro Mini at home. Being done, it’s not worth it. You can buy one for a dollar more than you can make them, and it took awhile to populate. Although, it’s “fun.”

This projects was also a chance for me to test the Spying-Stalactite I built.

I’ve enjoyed it. It allows me to reflect on my strategy while populating boards. It’s simply a drop down with some high-powered LEDs (~2500 lumen), heatsink, and coolant fan. It has a hole for my iphone to do the recording. Cheap and simple. Although, I need to diffuse the light, as you might see by the video that it washes out the details of the projects. Also, I’ll add a few more lights and do away with the tungsten lamp, since the iphone is constantly in a white-balance battle as I move infront of the mixed lightsources.

I populated this board; everything came out fine (although, it was much more difficult trying not to block the camera with my head). I popped it into Atmel studio and it read out the device voltage and signature. Of course, I bricked it, as I seem to do a lot.

My next projects is a Fuse Doctor. :)

I had ordered the boards from OSHPark and had planned on making three. So, I populated another and took some time programming it. I’ve outlined my steps below:

1. Hook up the AVRISP MKII

2. Open Atmel Studio. Go to Tools – Device Programming.

3. Setup:

  • Tool: AVRISP mkII
  • Device: ATmega328P
  • Interface: ISP

Click apply

4. Read Target voltage (it should be ~5V). Read Device Signature.

  1. Open boards.txt that comes with Arduino (\Desktop\arduino-1.0.3\hardware\arduino\boards.txt).

  2. Scroll down to the area marked:

8. Pull the programming information for the board from this area. Now, I’ve bricked a few boards, but I think I’ve figured this one out. When programming this board with the MKII and Atmel Studio, you should follow this order.

1. Set the fuses:

  • Extended: 0xFD
  • High: 0xDA
  • Low: 0xFF
  • (Double check the board file to make sure I didn’t make typos)
  • Hit “Program”

2. Upload Bootloader.

“The bootloader for the 5v, 16mhz Arduino Pro Mini (which is what I built) is “ATmegaBOOT_168_atmega328.hex (Desktop\arduino-1.0.3\hardware\arduino\bootloaders\atmega\ATmegaBOOT_168_atmega328.hex).
It’s important to note that the 3.3v and 5v versions use different bootloaders.

  • Go to the Memories tab
  • Hit the browse ellipsis.
  • Select the “ATmegaBOOT_168_atmega328.hex”
  • (Double check the boards file to make sure I’m not screwing you up).
  • Hit program.

3 Set Lock Bits.

  • Go to the “Lock bits” tab.
  • Check the boards.txt file for Lockbit number
  • Lockbit: 0xCF
  • (Double check the boards.txt. I don’t take blame for bricked boards :P).
  • Hit “Program”

9 Upload the Blink Sketch; the LED by the reset button should blink.

10 Let me know how it went. If you bricked a chip using these instructions, let me know so I can modify them quick.

Now that I’m used to the camera and stalactite, I plan to annotate my next board for tips on working with 0402s.

Hope all are well.

ps. Birdmun et al., sorry bout the copyright issues. Not a professional at anything, especially video editing :)

My Eagle PCB Walkthrough

Originally posted on www.letsmakerobots.com

Addendum: Please don’t watch my videos. After Birdmun’s comment I found Hack-a-Day has created better videos (shakes fist at Hack-a-Day) and I don’t want anyone to waste anyone’s time. Although, mine has a better soundtrack and less mutton-chops :)

Hack-a-Day videos:

  1. Learning Eagle CAD Part 1 – Schematic & Custom Parts
  2. Learning Eagle CAD Part 2 – Schematic & Custom Parts (includes making a part)
  3. Learning Eagle CAD – CAM Processor
  4. Learning Eagle CAD – Layout

Original: I was speaking with TeleFox and Birdmun about finding an optoisolator for use with my Raspberry Pi; I had gotten some samples of these ICs: ADUM1250ARZ. Well, for awhile now I’ve wanted to share my dumb-luck methods for designing a board around a sampled IC.

So here it is, 20mins (sorry).

Hope everyone is well :)

Part 1 – Making the Part

Part 2 – Finishing the Part and Making the Board

Finished Eagle Files: ADUM1250ARZ Breakout Board