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SPI Interface ad7714 - Atmega2560

Question asked by MarioE on Mar 12, 2015
Latest reply on Mar 29, 2016 by MarioE

I have a STK600 with an Atmega2560 with ad7714.

1)

My program works fine when the driver for the communication with the ad7714 uses program controlled SPI handling of IO ports, i.e. without SPCR, SPDR etc. After a switch to the CPU - supported SPI Interface (using SPCR, SPDR etc) i receive random numbers. The clock pulse width with rogram control ist about 15 yS, with CPU control, slowest mode (=1/(4000000/128)) i have a clock pulse width of 32yS. This means my program control - which works - is faster !! This means also: The speed, cabling etc can not be the cause.

 

2)

another version of my program (with an AD7793) runs with CPU supported SPI fine.

 

This means: AD7714 and AD7793 behave different on SPI bus.

 

My question is: what SPI Mode (0,1,2,3) must be used on ATMEGA2560 and what setting of PIN 4 (POL) of the AD7714 is correct?

I tried nearly all versions without success.

 

THX, Mario

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