For the community/users: A NO CODE FlexWire bandswitcher

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I'm building an amp with a bandswitcher for the front end filters.  To that end, I decided I'd present some information that will be useful to other experimenters.

The NXP  PCA line of chips are I2C to GPIO chips.  I've used the PCA9534 in other projects, and am now using it to pull FlexWire I2C data out and convert it to something useful.  I run the output from the PCA chip through a mosfet to switch relays in a bandswitcher.   Now you'll need to be able to command the bandswitcher to do what it is made for, and how exactly you do that is up to you, however, I can help you with the CAT commands.

First, you will need to initialize the PCA chip by telling it to set the GPIOs to output.  The only CAT command on my Flex1500 that works (once I made the mods to the PowerSDR software that I detailed in another post) is ZZFY.   The format of that command is ZZFY<deviceaddr><regaddr><data> for this conversation.  The deviceaddr value is the I2C device address.  The PCA chip provides three address lines which you tie high or low to control the I2C device address.  I tied all of mine high; so I will provide the calls I make under the assumption that you're doing the same.  I suggest you DO NOT tie all yours low since that will conflict with the Heros Preselector code in the PowerSDR software...  You never know when that code will jump out and hose your bands.  The address bits are the most significant 7 bits of the addressing byte, the least significant bit controls whether the I2C bus transaction is read or write.  The base address of the PCA chip is 0x40 (same as the Heros).  The address lines affect the low bits, so for my bandswitcher I have the address 0x4E.

On initialization, you need to set the register address 3 to 0x00.  Its default is 0xFF.  This CAT command will do it:


And your initialization is complete.

When you switch bands, remember, only one bit should be set at any time.  The register you want to set is address 0.   I have 6 filters on my bandswitcher, therefore, the following CAT commands switch through each of my bands:


Now how you enter your CAT commands is up to you.   I've requested (and gotten) the PowerSDR source code, so I'm actually going to put the bandswitching code into the controls (therefore not needing the CAT commands above) but since this is a NO CODE example, I thought you people would rather have CAT commands.
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Robert Stoddard

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Posted 2 years ago

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