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Looking for advice on micro-controller choice

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Junior Member level 2
Feb 27, 2006
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Los Alamos, NM
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I have a DDS based rf generator that I have been building for about 10 years. The current controller is a bit long in the tooth. I want to replace it. My current system uses a Sage (Rabbbit) RCM3400 on an eval board. These are custom built systems with varying specs so I have relied on development boards for the builds. With a new processor I want to start with a development board. My current system has about 200 k of C code. So right off I'd like at least 512 k of programmable memory. I am time multiplexing between receiving/sending TCP/IP over Ethernet with data acquisition that monitors the phase of the field of a resonant cavity to digitally phase lock the DDS source to the cavity frequency. I originally programmed with Rabbit Dynamic C, but I found a company that had a standard ANSI C compiler for the Rabbit. They also had worked out a time multiplexing scheme and converted my Dynamic C code for a reasonable consulting fee.

In addition to Ethernet capability, I need a modest amount of digital I/O, including at least one SPI channel. The Rabbit is an 8 bit processor but handles 16 bit calculations pretty well. My problem is that there is a lot to choose from and much of what I see seems tiny, cheap, and under powered.

I also need 8 channels of 12 bit ADC. I doesn't have to be super fast, but if I could read 8 channels simultaneously that would eliminate the need for an 8 channel sample and hold circuit. I've already been looking at chips that can do that. I don't expect to find an Eval board with that capability.

I an enamored of the Xilinx Zynq 7000 system. The coupled FPGA and two processors sound ideal for my needs. My current system uses an NI9606 as an 8 channel time base with independently variable delay and pulse width. I rely on my son-in-law to do the FPGA programming. The problem is that the NI hardware and software is too expensive. However, the learning curve for the Zynq 7000 is pretty steep.

Ideally I would like to hire a consultant who can give me a kickstart on the Zynq system to the point where I can modify the C code and ultimately the FPGA. Failing that I need something that is newer and a step up from the RCM3400.

The 8 channels simultaneously, what is the sample rate you need ?

Regards, Dana.

Then consider this using SOC (single chip, includes Vref) :


The above uses its two 12 bit SARS, single ended( you can config for differential), and mux, to do
2 MSPS (each channel running at 1 MSPS). DMA handles moving results. The muxes could be the
HW controlled mux, so when EOC of SAR occurs next channel auto selected, I just got lazy. Also
available OpAmps to G up the signal path if needed, although at these speeds I would look into
settling time to 1/2 lsb of 12 bits. If needed. DSP as well....This is all a single chip solution.

Right hand window shows resources used/left, most available for other tasks.

Whats onchip, multiple copies in many cases (not shown is ARM M3 core as well) :


Compiler and IDE free (PSOC Creator), board $ 15 to start with (depending on overall I/O
needed etc..

Company is Cypress, now owned by Infineon.

Regards, Dana.
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