Reverse Engineering LCD Displays

Dorkbot logo on a large LCD display

Over at DorkbotPDX in Portland, a member showed up with a stack of large LCD displays from point of sale terminals. [Paul] took it upon himself to reverse engineer the displays so that they can be recycled in future projects.

The control circuit for this LCD resides on a rather large PCB with quite a variety of components. The board was reduced to three main components: an MSM6255 display controller, a 32k RAM chip which is used as the framebuffer, and a tri-state driver.

With all the unneeded components out of the way, a custom board based around an ATmega88 MCU was added. This board was soldered in to interface with the LCD controller’s bus. This allows data to be written from the 128k flash ROM on the custom board into the frame buffer. Once this is done, the display controller will display the data on the LCD.

Now that data could be written, [Paul] figured out the correct configuration for the display controller. That was the final piece in getting images to show up correctly on the display. If you happen to find some old Micros 2700 POS terminals, [Paul]‘s detailed write-up will help you scavenge the displays.

Building new interfaces with an iPad

There’s a word – synchronicity – to describe two disparate events that occur together in a meaningful way. We see this a lot in the Hackaday tip line; two people send in somewhat similar hacks solving similar problems in similar ways nearly simultaneously. Here’s two builds by [Bryce] and [spektakx] that hit our inbox within minutes of each other that both implement existing interfaces with iPads.

iPad turntable controller

[spektakx] sent in an iPad powered DJ MIDI controller he built as a prototype to test out the size, orientation and layout for an upcoming build. The turntable controllers are simple USB affairs made to jog and scratch records digitally. Although [spektakx] admits it’s a little unfinished, it’s still just a prototype. Also, he can use a Windows 7 tablet laptop for ‘more suited’ hardware. Check out [spektakx]‘ video demo after the break.

an iPad cash register

[Hacktheory] found [Bryce]‘s Flickr photolog of a DIY ‘Square’ cash register. The electronics part of this build is practically non-existent; it’s just an iPad with a credit card readers that plugs into the headphone jack. Yes, we just saw these ‘Square’ credit card readers this last week. The fabrication portion of this build is incredible – [Bryce] has a few wonderful pieces of walnut there, and did an exceptional job with the wood work. It’s probably not well suited to high-volume retail, but we couldn’t think of a better cash register for a boutique shop.

[Read more...]

Generating music with credit cards

mozarts_credit_card

[Steve] was browsing around at a local electronics surplus store when he spotted an old Tranz 330 point-of-sale terminal that seemed pretty interesting. He took it home and after disassembling it, found that it contained a Z-80 based computer. Because the 330 shares the same processor as other hobbyist-friendly devices such as the TRS-80, he figured it would be quite fun to hack.

While the Z-80 processor is pretty common, [Steve] still had to figure out how it was interfaced in this particular device. After spending some time reverse engineering the terminal, he had free reign to run any program he desired. After thinking for a bit, he decided it would be cool to use the terminal to generate music based on whatever card was swiped through the reader – he calls his creation “Mozart’s Credit Card”.

He found that just playing sounds based on the raw contents of the mag strips didn’t produce anything coherent, so he wrote a small application for the terminal based on the Melisma Stochastic Melody Generator. Music is generated somewhat randomly using various card characteristics, as you can see in the video below.

We think it’s pretty cool, but [Steve] says he’s always open to suggestions, so let us know what you think in the comments.

[Read more...]

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