SAMD11 Provides Two Serial Ports For Price Of One

April 4, 2022 by Tom Nardi 22 Comments

While the average computer user likely hasn’t given much thought to the lowly serial port in decades, the same can’t be said for the hardware hacker. Cheap serial-to-USB adapters are invaluable for snooping debug ports or programming chips, and if you ask us, you can never have too many laying around the bench. [Quentin Bolsée] loves them so much that he’s even figured out how to build a dual-port adapter with a SAMD11C14 microcontroller.

As [Quentin] explains in the write-up, this isn’t just some kind of Y-cable. When connected to the host computer, the adapter shows up as two distinct serial ports, each with independent settings for things like baud rate and parity. This handy little gadget will let you tap into the serial ports of two devices simultaneously if you’re looking to do some Hollywood-style hacking, but more practically, it allows you to establish a debug and programming interface to the same board using just one USB connection.

[Quentin] milled a custom PCB for his adapter, which we have to say looks phenomenal, but those with more limited equipment at home should be able to send the MIT licensed board files off for production. He’s also provided the source code for the SAMD11C14’s firmware, so you’ve got everything you need to spin up your own version of this neat tool.

Two ports not enough for your parallel hacking needs? Believe it or not, we’ve also seen a quad USB-to-serial adapter that you can put together, though it’s a considerably more complex circuit.

ESP32 Serial Interface Modernizes Old Equipment

January 27, 2020 by Tom Nardi 25 Comments

There’s still plenty of useful hardware out there that uses an RS-232 interface, like the Behringer Ultradrive loudspeaker systems that [Lasse Lukkari] works with from time to time. Rather than ditch perfectly good gear because modern computers (to say nothing of phones or tablets) don’t have physical serial ports, he decided to come up with a WiFi adapter for these old devices that he calls SerialChiller.

Inside the SerialChiller is an ESP32, a MAX3232 line driver, a LM1117 linear regulator, and a few passives. The professionally manufactured PCB is housed inside of an enclosure that [Lasse] has repurposed from a cheap DB15 breakout adapter. The USB cable is used to power the board and for programming, though it can also be used to turn the SerialChiller into a USB-to-serial cable as well.

The hardware for this project is pretty straightforward, but what we really like is the direction he’s taken with the software. Rather than using the SerialChiller as a simple serial to WiFi bridge, [Lasse] is actually implementing a complete web-based interface directly on the microcontroller. In the video after the break he demonstrates his firmware for controlling the aforementioned Behringer Ultradrive, but that’s just one possible application for the project. Firmware could be spun up for all sorts of classic devices, breathing new life into hardware that might otherwise be in danger of heading to the landfill.

Of course, using the ESP family of chips as serial adapters is hardly anything new. In fact, that’s what they were designed for. But developing modern user interfaces for old hardware thanks to the power of the ESP32 has some fascinating potential.

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Finding A Cheaper USB To Serial Chips

December 2, 2014 by Brian Benchoff 90 Comments

FTDI-gate wasn’t great for anybody, and now with hardware hobbyists and technological tinkerers moving away from the most popular USB to serial adapter, some other chip has to fill the void. The cheapest USB to serial chip on the market appears to be the CH340G, available for 20-40 cents apiece from the usual retailers. There is, however, almost no English documentation, and the datasheet for the CH340 family doesn’t include this chip. [Ian]’s here to help you out. He got his mitts on a few of these chips and managed to figure out the pinout and a few reference schematics. He even made an Eagle part for you. Isn’t that nice?

The CH340 series of chips do exactly what you would expect them to do: a full-speed USB device that emulates a standard serial interface, with speeds from 50bps to 2Mpbs. The chip supports 5V and 3.3V, and all the weird modem lines are supported. This chip even has an IrDA mode, because wireless communication in the 90s was exactly as rad as you remember.

With [Ian]’s help, we now have a cheap source of USB to serial chips. If you need the datasheet, here you go. The driver is a bit more difficult to find, but what you’re looking for is the CH341 family of chips. That can be found with a little bit of Google fu.