I caught on to a promotion from AVNet last week, in which one may get a free MAX5214 eval board (available through August 31), so hopped on it because really, why wouldn’t I turn down free hardware? I promptly forgot about it until today, when a box arrived from AVNet.
What’s on the board
The board features four Maxim ICs:
- MAX8510- small low-power LDO. Not terribly interesting.
- MAXQ622- 16-bit microcontroller with USB. I didn’t even know Maxim make microcontrollers!
- MAX5214- 14-bit SPI DAC. The most interesting part.
- MAX6133- precision 3V LDO (provides supply for the DAC)
The MAXQ622 micro (U2) is connected to a USB mini-B port for data, and USB also supplies power for the 5V rail. The MAX8510 (U4) supplies power for the microcontroller and also the MAX6133 (U3). The microcontroller acts as a USB bridge to the MAX5214 DAC (U1), which it communicates with over SPI. The SPI signals are also broken out to a 4-pin header (J6).
The software included with the board is fairly straightforward, providing a small variety of waveforms that can be generated. It’s best demonstrated photographically, as below. Those familiar with National Instruments' LabView environment will probably recognize that this interface is actually just a LabView VI (Virtual Instrument).
Rather more interesting than the stock software is the possibility of reprogramming the microcontroller. Looking at the board photos, we can see that there’s a header that breaks out the JTAG signals. With the right tools, it shouldn’t be very difficult to write a custom firmware to open up a communication protocol to the device (perhaps change its device class to a USB CDC for easier interfacing). Reprogramming the device requires some sort of JTAG adapter, but I can probably make a Bus Pirate do the job.
With some custom software, this could become a handy little function generator- its precision is good and it has a handy USB connection. On the downside, the slew rate on the DAC is not anything special (0.5V/µs, -3dB bandwidth is 100 kHz), and its output current rating is pretty pathetic (5 mA typical). With a unity-gain amplifier on the output though, it could easily drive decent loads and act as a handy low-cost waveform generator. Let’s get hacking?