A Tool For Spying On Serial Data

[Piotr] was working on a recent Arduino project when he ran into a problem. He was having trouble getting his Arduino Pro Mini to communicate with an ESP8266 module. He needed a way to snoop on the back and forth serial communications. Since he didn’t have a specialized tool for this task, [Piotr] ended up building his own.

The setup is pretty simple. You start with a standard serial cable containing the TX, RX, DTR, and GND wires. This cable connects the Arduino to the ESP8266 WiFi module. The TX and RX lines are then tapped into. Each wire is routed to the RX pin of two different serial to USB adapters. This way, the data being sent from the Arduino shows up on one COM port and the data being transmitted from the module shows up on the other.

The next piece of the puzzle was coming up with a way to see the data more clearly. [Piotr] could have opened two serial terminals simultaneously, but this wasn’t ideal because it would be difficult to compare the timing of the data. Instead, [Piotr] spent less than an hour writing his own simple serial terminal. This one connects to two COM ports at the same time and prints the data on the same screen. The data from each COM port is displayed in a separate color to make it easy to differentiate. The schematic and source code to this project can be found on [Piotr’s] website.

Hackaday Prize Entry: BS Free USB

Take a look at some old electronics magazines, or even a few blog posts from 10 years ago, and you’ll notice something strange: parallel ports. Those big ‘ol DB25 were the way to get bits out of a computer and into a microcontroller. There was a reason for this: it was exceptionally easy to do.

Now, we have USB to deal with, and that means VIDs and PIDs, drivers, enumeration, and a whole bunch of cruft that makes blinking an LED a surprisingly complicated process. [Colin O’Flynn]’s project for the 2015 Hackaday Prize aims to fix that with BSU – BS Free USB.

Instead of USB to serial chips attached to another microcontroller, [Colin] is using a few microcontrollers with a built-in USB interfaces. These chips are loaded up with firmware and controlled with a simple API on the computer side. If you want to blink a pin, just add a library to your project and set the pin high. Want some SPI on your computer? That’s just setting a few pins as MOSI, MISO, and SCK and typing in a few bytes. It’s basically a $2 Bus Pirate that you can stick into any project.

If [Colin]’s name sounds familiar in the context of The Hackaday Prize, it’s because he won second place with the ChipWhisperer last year. While a tiny USB thing isn’t quite as cool as a tool to break embedded encryption, the BSU certainly seems more useful to millions of hardware tinkerers around the world.


The 2015 Hackaday Prize is sponsored by:

VCF East X: The World’s Largest USB Thumb Drive

The Vintage Computer Festival last weekend featured racks and racks of old minicomputers, enough terminals for an entire lab, and enough ancient storage devices to save a YouTube video. These storage devices – hard disks, tape readers, and 8″ disk drives – were only connected to vintage hardware, with one exception: a DEC RL02 drive connected to a modern laptop via USB.

The DEC RL02 drive is the closest you’re going to get to a modern mechanical hard drive with these old machines. It’s a huge rack unit with removable platters that can hold 10 Megabytes of storage. [Chris] found one of these old drives and because he wanted to get into FPGA development, decided to create a USB adapter for this huge, old drive.

The hardware isn’t too terribly complex, with a microcontroller and an FPGA that exposes the contents of the drive over USB mass storage. For anyone trying to bootstrap a PDP-11 or -8 system, [Chris] could download disk images from the Internet, write them to the disk, and load up the contents of the drive from the minicomputer. Now, he’s using it with SimH to have a physical drive for an emulated system, but the controller really doesn’t care about what format the disk pack is in. If [Chris] formatted a disk pack with a FAT file system, he would have the world’s largest and heaviest USB thumb drive in the world.

Video below.

Update: As promised, [Chris] put all the code in a git

Continue reading “VCF East X: The World’s Largest USB Thumb Drive”

More Power For Raspberry Pi USB Ports

Since the Raspberry Pi 2 was released, everyone building RetroPi emulators has been graced with four USB ports. For those of us doing useful stuff with the Pi, those ports are a little anemic: you can’t plug in a webcam and a WiFi module at the same time without suffering CPU brownouts. The maximum current all USB peripherals can draw from the USB port is 600mA. By changing a value in the /boot/config.txt file, this current limit can be increased to 1.2A for all four ports.

Pisquare
The yellow line traces the signal from the GPIO to the USB power switch.

Because the USB current limit is set in software, there must be a few bits of hardware that do the actual work. Tucked away below the right hand of the GPIO header is the hardware that does exactly that. It’s an AP2253 current-limited power switch (PDF), and the current is adjustable by tying a resistor to pin 5 on the chip.

Pin 5 on the AP2253 is connected to two resistors. One resistor goes directly to a ground plane, while the other is switched through a FET. The gate of this FET goes to another resistor, and when a GPIO pin is high, these resistors are wired in parallel. This means the resistance is halved when the GPIO pin is high, doubling the current limiting circuit in the AP2253.

This setup provides a relatively easy mod to increase the current limiting of the USB ports so they can provide 4x500mA, meeting the USB spec. The AP2253 power switch’s current limiting can be set by a single resistor, anywhere from 10kΩ to 232kΩ. By removing R50 and R4, and replacing R50 with a 10kΩ resistor, the current limiting of the AP2253 switch will be set to its maximum, 2.1A. Divide that by four, and you have 500mA per port, just like every other computer on the planet.

There is a reason the Raspberry Pi foundation set the current limiting of the USB ports so low. The Pi was originally intended to run off of a micro USB phone charger. There aren’t many phone chargers out there that will supply more than 1A, and the CPU and related peripherals will take half of that. If you’re going to change the /boot/config.txt file, you’re going to need a beefy power supply. Increasing the current limiting of the USB ports to 2A will require an even bigger, beefier supply.

USB PIDs For All

The USB Implementers’ Forum doesn’t make things easy for anyone building a product with a USB port. To sell anything with USB and have it work like USB should, you need to buy a USB Vendor ID, a $5000 license that grants you exclusive use of 65,536 USB Product IDs. Very few companies will ever release 65,000 products, and there are a lot of unused PIDs sitting around out there.

Now, someone has finally done the sensible thing and put an unused USB VID to work. pid.codes obtained the rights to a single VID – 0x1209 – and now they’re parceling off all the PIDs that remain to open source hardware projects.

This is not a project supported by the USB Implementers’ Forum, and is more of a legal game of chicken on the part of pid.codes. The only thing the USB-IF could do to stop this is revoke the original VID; useless, because they can’t reassign it to anyone else. The original owners of the VID, InterBiometrics, licensed their VID before transferring or sublicensing VIDs and PIDs was prohibited by the USB-IF.

You can get a PID by forking the pid.codes repo, claiming a PID, and sending a pull request. Once that’s accepted, that PID is yours forever.

Solar Charge Controller Improves Efficiency of Solar Panels

The simplest and easiest way to charge a battery with a solar panel is to connect the panel directly to the battery. Assuming the panel has a diode to prevent energy from flowing through it from the battery when there’s no sunlight. This is fairly common but not very efficient. [Debasish Dutta] has built a charge controller that addresses the inefficiencies of such a system though, and was able to implement maximum power point tracking using an Arduino.

Maximum power point tracking (MPPT) is a method that uses PWM and a special DC-DC converter to match the impedance of the solar panel to the battery. This means that more energy can be harvested from the panel than would otherwise be available. The circuit is placed in between the panel and the battery and regulates the output voltage of the panel so it matches the voltage on the battery more closely. [Debasish] reports that an efficiency gain of 30-40% can be made with this particular design.

This device has a few bells and whistles as well, including the ability to log data over WiFi, an LCD display to report the status of the panel, battery, and controller, and can charge USB devices. This would be a great addition to any solar installation, especially if you’ve built one into your truck.

This is [Debasish]’s second entry to The Hackaday Prize. We covered his first one a few days ago. That means only one thing: start a project and start documenting it on hackaday.io

Killer USB Drive is Designed to Fry Laptops

[Dark Purple] recently heard a story about how someone stole a flash drive from a passenger on the subway. The thief plugged the flash drive into his computer and discovered that instead of containing any valuable data, it completely fried his computer. The fake flash drive apparently contained circuitry designed to break whatever computer it was plugged into. Since the concept sounded pretty amazing, [Dark Purple] set out to make his own computer-frying USB drive.

While any electrical port on a computer is a great entry point for potentially hazardous signals, USB is pretty well protected. If you short power and ground together, the port simply shuts off. Pass through a few kV of static electricity and TVS diodes safely shunt the power. Feed in an RF signal and the inline filtering beads dissipate most of the energy.

To get around or break through these protections, [Dark Purple]’s design uses an inverting DC-DC converter. The converter takes power from the USB port to charge a capacitor bank up to -110VDC. After the caps are charged, the converter shuts down and a transistor shunts the capacitor voltage to the data pins of the port. Once the caps are discharged, the supply fires back up and the cycle repeats until the computer is fried (typically as long as bus voltage is present). The combination of high voltage and high current is enough to defeat the small TVS diodes on the bus lines and successfully fry some sensitive components—and often the CPU. USB is typically integrated with the CPU in most modern laptops, which makes this attack very effective.

Thanks for the tip, [Pinner].