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Author Topic: Has anybody implemented a homebrew RS232 interface for DDS VFO?  (Read 3685 times)
N1EU
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Posts: 16




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« on: March 02, 2013, 02:37:41 AM »

Many Ten-Tec Corsair owners have installed DDS VFO designs by N4YG, G3TXQ, etc.  I'm a big Corsair fan and have a real interest in combining this with a rudimentary RS232 interface so that a computer logging program could get/set rig frequency (realizing band still needs to be set manually).  I imagine that a small subset of an existing rig command set could be implemented.

Has anybody heard of a similar homebrew project that has been documented?  I assume there is no product available that does this.

Thanks & 73,
Barry N1EU
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TANAKASAN
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Posts: 933




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« Reply #1 on: March 02, 2013, 09:04:42 AM »

http://www.amqrp.org/projects/serialDDS/index.html

Go on, ask me a hard one next time  Grin

Tanakasan
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W9GB
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« Reply #2 on: March 02, 2013, 12:08:45 PM »

Since N4YG uses a MicroChip 40-pin PIC (16F877, 16F452 ?), a better question is:
Why is this option (external access to serial I/O on PIC) not available with his DDS board?

Here is an example (Sparkfun 40-pin PIC prototype board, PIC-P40B) with a Maxim MAX232
for a standard RS-232 port.  
http://www.sparkfun.com/datasheets/PIC/pic-p40b.pdf
Based on a 2002 Olimex PIC board.
https://www.olimex.com/Products/PIC/Proto/PIC-P40-20MHz/
« Last Edit: March 02, 2013, 12:26:20 PM by W9GB » Logged
N1EU
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Posts: 16




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« Reply #3 on: March 02, 2013, 12:33:02 PM »

Yes, I wish the option was available on N4YG's product.

I will take a closer look at the AmQRP serial DDS, but it looks like they didn't implement/emulate any rig's existing CAT commands on a rudimentary level.  But their work would be quite helpful to anyone wanting to do so.  I will investigate further - thanks!

73,
Barry N1EU
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TANAKASAN
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« Reply #4 on: March 03, 2013, 07:37:58 AM »

I would love to find a way to add CAT control to my homebrew gear. The three DDS chips in the rig are already under microprocessor control but I have no idea where to start.

Having said that.............

It would be nice if CAT could be dragged kicking and screaming into the 21st Century with control over USB rather than an RS-232 cable. The only people I know who have come close to this are Icom with the IC-7600 but I'm willing to be proved wrong.

Tanakasan
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N3OX
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« Reply #5 on: March 03, 2013, 10:25:23 AM »

It would be nice if CAT could be dragged kicking and screaming into the 21st Century with control over USB rather than an RS-232 cable. The only people I know who have come close to this are Icom with the IC-7600 but I'm willing to be proved wrong.

I think there might be some others... I guess the Elecraft K3 can have a USB to serial inside the case?

Yeah I just keep buying USB-to-TTL-serial adapters and using those... here's one all done up with the adapter close to my Kenwood TS-440S.  http://n3ox.net/files/kenwood-cat.jpg

One issue is compatibility with useful legacy equipment though. If you have an ordinary serial port on the back of the radio, $15 and some wiring can turn it into a USB serial port. If you just have a USB jack and want to hook up your old amplifier that sent and received CAT commands without a computer in the mix?  Good luck.

There's no real reason why you couldn't offer both on the back panel, though, and built-in USB would be nice.

Quote
I would love to find a way to add CAT control to my homebrew gear. The three DDS chips in the rig are already under microprocessor control but I have no idea where to start.

Did you write the code for your microcontroller? Does it have a serial port? I haven't done a ton with CAT yet but I have set up an Arduino to request frequency information from Ham Radio Deluxe (should be straightforward with any microcontroller with a serial  port)

Here's some Arduino code to set the frequency of a DDS module (from Ebay, essentially identical to this http://www.ebay.com/itm/DDS-Signal-Generator-Module-AD9850-0-40Mhz-Sine-Square-Wave-/321057477882?pt=LH_DefaultDomain_0&hash=item4ac08454fa but from seller ci_tynight209)

http://n3ox.net/files/sketches/serial_interface_AD9850_0_2.pde

and here's some code that talks to Ham Radio Deluxe to read frequency (and in this case set a pattern of lines on a shift register for station control, emulating a parallel port used for antenna switching etc)

http://n3ox.net/files/sketches/parduino_v_1_1.pde

It's been a long time since I played with the second code.

A proper combination of those two would be useful to, say, synchronize the frequency of the AD9850 DDS with another radio. That's actually a planned thing here because a CAT-controlled radio synchronized with a signal generator and a soundcard input can make for a pretty useful scalar network analyzer Smiley But I haven't put both of those things together yet.

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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
N1EU
Member

Posts: 16




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« Reply #6 on: March 03, 2013, 11:02:46 AM »

For someone starting from scratch and wanting to homebrew a DDS VFO w RS232, would you recomment going the PIC route or the Arduino route?  (i.e., no knowledge yet of programming either)

Thanks & 73,
Barry N1EU
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N3OX
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« Reply #7 on: March 04, 2013, 05:30:43 AM »

I haven't done any projects with PIC but the Arduino programming environment and libraries for doing different tasks have been developed with completely new people in mind. I think there are some ways that it would be simpler to learn, including ample "hand-holding" examples online.

A disadvantage for high-performance stuff is that a library that gives you a nice intuitive function name that behaves a certain way even if you do something a bit weird might require dozens of lines of actual microcontroller instructions, making it kind of slow and making it take up maybe more memory than it has to. But that hasn't really been a problem for most of my projects yet.

The programming can be similar, some people write code in C for PIC and have a translator to the required chip instructions, (largely) just like the Arduino. For more flexibility but more difficulty, you would program in assembly language which often seems to be some hams' approach.

PIC might give you more ability to directly re-use code for ham radio projects; a lot of hams have been using it for a long time.

In my opinion the abstraction of programming in the Arduino environment with bunch of libraries with descriptive names makes it easy to learn Arduino... it's what finally got me to try microcontrollers at all. The high extra cost of an Arduino board is significant (though you can roll your own minimal one fairly easily once you're up and running). But the all-in-one approach means your programmer and chip are all there out of the box and maybe you don't have to debug hardware at first... and I also think that for projects that communicate with the computer, the cost is much more reasonable because the USB port is already there.

I've started to hit a few limitations of the Arduino's tendency to "hide" low-level stuff from the user, and so I'm just starting to think about branching out... but I think for a simple RS232 DDS VFO you might get off the ground quicker with Arduino. Hopefully someone with actual PIC experience will comment further.
« Last Edit: March 04, 2013, 05:34:41 AM by N3OX » Logged

73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
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