Have you wondered how to connect to the Jetson TK1 J3 headers in a more permanent fashion? One way to do that is to build a board, the Jetson TK1 Connector board, which has connector pins attached. Received the boards, looky here:
Over the last few months, we’ve been running through a series of articles on how to communicate with external devices through the J3 headers on the Jetson TK1. These articles include most of the different types of I/O that the Jetson provides such as UART, GPIO, and I2C. One of the questions is how to make a more permanent connection than just shoving hookup wire into the headers.
In comparison to products such as the Arduino and Raspberry Pi, the Jetson has a different sized GPIO header. The spacing on the header is 2.0mm on the Jetson versus 2.54 mm on the hobbyist boards. While this provides access to more signals in a compact space (after all there are 125 pins all together on the Jetson!), it also means that it is more difficult to interface with common breakout boards and prototyping tools used in the “maker” community. In other words, if such interface work is not your day job, things may be a little challenging.
One way to make this simpler is to build a circuit board that connects to the Jetson headers and converts the signals to a different physical layout, more like the hobbyist boards. But then you have to layout a circuit board, and make sure everything is wired up correctly. While laying out circuit boards is relatively straightforward, it’s hard to expect someone to eagerly jump right in and build their own circuit boards so that they can interface to some hobbyist devices.
As it turns out, Dr. David Cofer over at NeuroRobotic Technologies noticed that the Jetson ecosystem was missing just such prototyping tools. Plus, Dr. Cofer does this type of work as his day job. There’s been an iteration of several different boards to interface with the Jetson, which are coming soon to a Kickstarter campaign near you. Go to the Jetduino page to get a feel for the capabilities of one of the boards. Money quote:
The Jetduino will also have a large prototyping area available where users can solder in their own components and hook it to either the Arduino, or directly to the GPIO pins of the Jetson. The prototype area will also break out connectors for all of the major GPIO, I2C, and SPI pins available on the Jetson’s header. Most importantly though, these connectors will already be level shifted from the Jetson’s 1.8 V to a user configurable higher voltage, typically 3.3V for use with the Due, or 5V for use with the Mega. This will make the Jetduino a very convenient tool for doing any type of prototyping with the Jetson. Just plug it up to your Jetson and you will automatically have all the GPIO, I2C, and SPI pins ready and waiting for you to use without having to worry about frying your Jetson or Arduino.
In the meantime, one of the early circuit board prototypes that simply brings out most of the interesting Jetson header signals to a 40 pin, 2.54mm header (named the Jetson TK1 Connector) has graciously been made available as an open source project. The complete DesignSpark PCB designs links for both a Level Shifter prototyping board and the Jetson TK1 Connector are available on the Using Jetson TK1 connector and level shifter for 25 MHz SPI data transfers page. For convenience, here is a zip file of the board project.
This connector board does not have built in level shifting in and of itself, but it makes it much more straightforward to build proto-boards where there’s no worry about wires coming loose. Like on a JetsonBot, just sayin’. Another advantage of this arrangement is that a ribbon cable can be used to transfer the signals to another board. This also makes it easy to “wrap” the ribbon cable so that the proto-board can be placed underneath the Jetson to help minimize the footprint.
The boards shown above were ordered from SeeedStudio Fusion and took a couple of weeks from the time of order to delivery. The boards are produced in China, I am located in California. As a note, the shipping charges were more than the cost of the boards themselves.
In ordering, I made the mistake of not ordering the boards assembled. At the time I thought it would be a good way to spend some quality time with the soldering iron and practice. Now that the boards are here, confronting the stark realization that there are 140 pins times 10 boards to solder up, and that 2.0mm spacing is really pretty tight, I’m thinking that I might not have really wanted that much practice. The more you know.