Cool Cap Engineer

Engineering by an anime nerd

Mojo Makes FPGA Board Design Open Source

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Last January, I’ve been learning how to use FPGAs, which I talked about in my Getting Started With FPGAs post.  To learn how to use FPGAs, I brought FPGA development boards, which can cost up to $110, from Digilent.com. Fast forward to March, and I found Mojo, an open source $75 FPGA development board, on Kickstarter.com. Based on what I’ve seen and tested thus far, I honestly think the Mojo board is a great introduction to digital design for electronic hobbyists and electrical engineering students.

What’s Under The Hood?
Unlike the Basys 2 that I commonly use, the Mojo uses a Spartan 6 XC6SLX9 FPGA. The Spartan 6 uses a 50MHZ clock, which is 10MHZ higher than the maximum clock frequency that a PIC18F can run.  In layman terms, it can run faster than most of my microcontroller/FPGA boards. The board can accept between 5V-12V, but can only output 3.3V for each digital I/O pin. Because of the Mojo’s 3.3V limitation, you’ll need extra hardware to use electronic items like servos, solenoids, etc. Finally, the Mojo uses an Atmega16U4 for the USB connection among other things.

What’s So Special About The Mojo?

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The Mojo board is geared towards making digital design easy for hobbyists and electrical engineering students by taking advantage of the board’s Atmega16U4 microcontroller, which is used to implement your digital designs on to the board. However, the Atmega16U4 is not just used for uploading your designs to the Mojo. The Atmega16U4 is used to communicate serial objects like serial LCDs, XBee wireless modules, and even Sparkfun’s FTDI breakout boards, with the Mojo.  You can even use the analog to digital converters included with the Atmega16U4 to allow the Mojo to take in analog signals.

What I Love About The Mojo ?

Although this seems like a petty thing, one of the key qualities I look for in a FPGA development board these days is the number of accessible I/O pins.  When I first heard that the Mojo will offer 84 accessible I/O lines, I immediately gave my pledge for the project  In fact, the lack of accessible pins for the Basys 2 FPGA board severely limited me in terms of FPGA projects. Embedded Micro even added 8 LEDs on the board for FPGA beginners to use. These LEDs are prefect for beginners as they implement simple modules using these LEDs. During the early stages of testing the board, not only did I create a blinking module for one LED, but I also used the same module to control the other seven LEDs on the board.

Despite the sheer number of I/O pins available, one cannot forget the fact that the Mojo is open hardware, which simply means that the Mojo’s schematic is available to view. This is crucial if you want to create your own FPGA development board, but do not know where to start. In fact, I will probably use the Mojo’s schematic in the future.

Work Done Thus Far ?

mojoservoCurrently, I do not have any project plans for the Mojo board. My focus has been learning how to effectively use the Mojo board. Recently, I learned how to control a servo using the Mojo board, even though most servos can only powered using 5V. I was able to control the servo by connecting one of the Mojo’s pins to the optoisolator’s input pin, and the servo’s signal pin to the optoisolator’s Vo pin. Although I could not find a power supply around, I used my Arduino board to provide the right power to the servo.

Where Can I Learn How To Use The Mojo Board?

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Although I am planning to write tutorials on how to use the Mojo board for this blog, you can visit Embeddedmicro.com, where you can read tutorials on how to implement serial communication, servo control, and other digital modules onto the Mojo. If you want to purchase your own Mojo board, then visit this URL. Please keep in mind that the Mojo board only cost $75.

Did anyone buy a Mojo board aside from me? Feel free to leave a comment about your impressions of the Mojo board!

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