Part Number: LMH6517
I am trying to program the gain of the LMH6517 via SPI using a beagleboard, but that does not seem to work. I already checked the communication lines on the oscilloscope and everything seem fine, so I would like to know if anyone can help identify what the problem is.There is some fixed gain there because I get an amplified signal out of it, but it does not change. The latch pin should not matter when spi is in use so I wonder what could be happening.
This would be the python code:
from Adafruit_BBIO.SPI import SPI
spi = SPI(1,0) #configure device and bus at beagleboard
spi.msh = 10500000 #clockspi.bpw = 16 #bits per word
spi.open(1,0) #opens it
spi.xfer2([128,0]) #transmits data
In reply to JPL:
It was just a probe issue here, the signals are correct... I am back to the start.
Since I get the signal transfer if I use just the beagleboard and connect MISO/MOSI together, the problem would not have been there I guess.
On page 13 here the SPI settings are given, I tried changing the mode before and it didn't help. Just to be on the safe side, it should be mode 3, am I right?
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Jacob Freet High Speed Amplifiers
In reply to Jacob%20Freet:
Hi Jacob Freet,
Even when sending like that the chip does not respond, I get the same constant gain when sending these commands for example:
I redesigned my board to use the LMH6517 on pulse mode, I don't know what is happening with the SPI. I tried programming a different PGA here that I also designed a circuit using SPI and for the other one my code worked, so I guess the LMH6517 requires something else that I was not able to find out.
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