Serial communications are a mainstay of digital computing. They don’t require much physical infrastructure and they exist in variations to fit almost any application. The behaviour of serial communications lines, varying from high to low voltage in a timed pattern, is analogous to a 1-bit DAC. Using a whole DAC for serial communication would be a waste in most cases, but the [RobotsEverywhere] team found an exception which you may have encountered already.

Since the audio output of the Android is accessible and addressable, [RobotsEverywhere] wrote source code to use the left and right channels as separate serial communication lines. This circumvents the need to bust into the device and muck about with the hardware which is great if you want a no-risk hack that allows communications to an RS232 port. Any hardware on which you can write to the DAC (and control the sampling rate) is a potential target.

There are some external electronics required to convert the audio signal to TTL, but it’s not very complicated–a couple of comparators and change. You can see it in action after the break.

As a bonus, when you’re done for the day you can plug in your headphones and listen to the soothing poetry of pulse waves all night long.

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Non acronym version of the title: send and receive text messages via cell phone communication towers using an Arduino or other microcontroller. “We’ve been doing that for years!” you cry, well yes, technically. But [Fincham] lays it outs simply; commercial offerings are expensive and finding a cell phone that uses RS232 now a days is getting difficult, so a new way of doing the same old is necessary. The good news is USB GSM modems are readily available, cheap, and only require a few interface pins to get them talking with an Arduino. In fact, the image above is all you need.

We love hacks that take quality products and make them better. This enhanced firmware for the VCI-100 is a great example of that. In a similar fashion as the Behringer hack, [DaveX] reverse engineer the firmware for the device and figured out a few ways to make it better. It improves the scratch controller and slider accuracy to use 9-bit accuracy from the ADC readings, which in the stock version were being shifted down to 7-bits. There’s also a few LED tricks they call Disco Mode. They’re selling a “chip” that you need to flash the firmware but from what we can see it’s simply an RS232 converter so you might be able to figure out how to work without that part. We’ve embedded a demo of firmware version 1.4 after the break.

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You get what you pay for. [Jkx] wanted to see how a USB to RS232 cable could be sold for just $1.70 and found out that it’s not actually RS232 compliant. The cable communicated as TTL levels, not the 12V expected of RS232 (although it can handle 12V incoming). He didn’t really want to use them for their intended purpose anyway. By betting rid of the DB9 plug and reusing the enclosed circuit board he now has a really cheap way to interface a microcontroller with the Universal Serial Bus. He worked out a couple of short subroutines that take care of receiving and sending data over the connection.

Here’s a serial to Ethernet module that you won’t have to write firmware to build. It uses a Lantronix XPORT module which takes care of all the work for you, including an embedded webserver. Both RS232 and RS485 data buses are connected to the XPORT serial input via a level converter to step the signal down to 3.3V. This solution comes at a price because of the ethernet module, but it would make a nice prototyping tool for testing projects that work on the two serial protocols.

[Geordy] added a serial port to his Zipit. It uses a 3.5mm jack as the connector. He managed to include an RS232 level converter inside the case. Both components were hard to fit into the cramped quarters but he did it and he kept the hacker-friendly device looking nice too.

If you’re attached to that favorite DB-9 interfaced device you should look into this part. FTDI is selling a USB-RS232 adapter as a replacement for DB-9 connectors. They come with USB male or female connections depending on the application and have the same serial footprint and pinout to which you’re accustomed. Using converter cables is just fine but this simplicity requires a few minutes of desoldering, rather than redesigning, etching, and populating a board in order to give that older design built-in USB connectivity.

[Thanks Juan]

The DJHI 2.8 is now available for preorder. The DHJI acts as an alternative serial connection in order to protect the Didj from the 12V signals it would be exposed to with a direct serial connection to your PC. It also adds in a microSD card slot and makes the connection process as simple as plugging it into the cartridge slot.

[The Moogle], who was the winner of our second Barcode Challenge, also tipped us off about his hack that upgrades the Didj to 64 Mb of RAM.