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ADA2200 SPI Interface MSB and LSB use

Question asked by ddudley on Apr 26, 2017
Latest reply on Apr 26, 2017 by brianharrington

I'm working on a design for an LVDT interface using the ADA2200.

 

I've had nothing but problems with this getting it to interface with a TI TM4C129X microcontroller, but I think one of the problems I'm having concerns the LSB bit in the Serial control register.

I'm trying to program a multi-register sequence into the chip.  So far, this has not worked successfully, or reliably.

If I understand the documentation correctly, with the LSB bit zero'd,, I should be providing the highest register number I want to program in the first transaction, and the register pointer will decrement?

Why would you then call the bit in the serial interface register 'Increment'?  From the datasheet, apparently it's only a increment in the LSB mode.  The bit should have been called increment/decrement or something that made sense.

 

And who's the idiot that decided to cram this thing into a 16 bit package?  The decision to multiplex the SDO/RCLK signal onto a single pin just to keep the chip in 16 pins was stupid, and is what has caused me endless headaches over the past week.  Would have been marvelous to have direct access to the Fsi signal as well.  I'm having to regenerate it from the SYNCO and CLKIN signals.

 

Sorry for venting - Just a week of frustration on one single part.  All SPI parts from all the other vendors are operating as expected, this one has just delayed me.

 

David

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