GPS For A Graphing Calculator

GPS [Chris], graphing calculator hacker extrordinaire, has seen a few of his projects show up on the front page of Hackaday, mostly involving builds that turn graphing calculators like the TI-84 Plus shown above into something that copies a few features from a smartphone. His latest build, a hardware GPS module attached to the TI-84 Plus, is yet another feather in his cap of awesome and impractical addition to a classic piece of hardware.

There were two major technical challenges behind adding GPS to a graphing calculator. The first of these was powering a GPS sensor. Many a calculator modder has put a lot of work into documenting the USB port on the 84 Plus, revealing it is a USB OTG port, capable of serving as a host or device. It also supplies 5V of power to just about anything, burning through batteries as a result.

The next challenge was reading the data coming off the GPS sensor at 4800bps.The TI-84 Plus series of calculators have a series of interrupts that can fire at fractions of the 15MHz clock. By setting the timer up to fire every 197 clock ticks and dividing again by 16, [Chris] can read data at 4758.9bps. It’s close enough to get most of the data, and the checksum included in the NMEA protocol allows the software to discard bad messages.

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Hackaday Links: July 31, 2011

Indestructible earbuds

We’re still waiting for our [Lt. Uhura] style earbuds. But until then, can we interest anyone in a set that will stand up to some abuse?

Solder Pot Scavenger

[Felicitus] says we should get a solder pot and use it to scavenge for parts. His method looks pretty easy and it’s cheaper than buying a rework station for this purpose.

Smartphone cooling

Turn all your hacking skills loose to beat the heat. That’s what [Stephanie] did when she added iPhone control for an oscillating fan.

Tunes calculator

Graphing equations and crunching numbers wasn’t enough for [Drew]. He went and figured out how to make his TI-84+ play music off of a thumb drive.


Don’t let anyone out-geek you at company parties. Beef up your arsenal with this resistor color-code necktie. And yes, you can wear it with a T-shirt!

Global CALCnet: your TI-83 just acquired Internet

Global CALCnet lets you connect your TI graphic calculator to the Internet and use your favorite services like instant messaging and Internet relay chat. It also provides the option of worldwide multiplayer functionality for games ported to the device such as Scorched Earth and Tetris. We looked in on [Christopher Mitchell's] CALCnet in December when it was being used to create local area networks with the adding machines. He’s taken that up a notch with a helping hand from Arduino. An Arduino board is used to connect the serial communications from the calculator to an Internet connected PC via the Arduino’s USB capabilities.

Think this will waste a lot of time in schools? Unlikely since an Internet connected computer is integral for this system to work. If you have a computer in front of you why waste time on the calculator network? Still, how hard would it be to build a WiFi module that can directly connect them to an access point? That may be a moot point as the Slashdot article that pointed us to global CALCnet also links to a calculator port of DOOM. It runs quite well, as you can see in the video after the break. This is a must-have for anyone owning a TI Nspire that can run it.

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Touch screen for graphing calculator

[Owen] got down and dirty by adding a touchscreen to his TI-84 graphing calculator. The dirty part is the z80 assembly code he wrote to use the linkport as a UART (assembly always makes us feel queasy). Once that was working he implemented some commands using an Arduino and then hooked up an Nintendo DS touch screen. Now he’s got this proof of concept video where he draws on the screen, that input is interpreted by the Arduino, commands are sent through the UART, and the calculator program draws on the screen. Adding a touch screen to something is a lot more impressive when you have to go to these lengths to get it working. Nice job!

ti-84 LED mod

Add lights to your graphing calculator. Do it now. [Sil3ntP8nd8] added some, and seems to have done a decent job. They are spread around the back, supplying a nice even light on, well, on whatever is under your calculator. It may be difficult to see too much detail though on account of the water marks. You have to protect your intellectual property though. This almost compares to the DS LED monstrosity we covered recently.