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
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In reply to Sean Cashin:
The configuration pins are set to:
ENA = +3.3V
ENB = +3.3V
LATA = GND
LATB = GND
MOD0 = GND
MOD1 = +3.3V
In reply to JPL:
I am using a beagleboard black and programming in python which I am not very experienced with. Signals for clock, cs, sdi and sdo were checked on oscilloscope and apparently seem ok. The basic code is the one I send above and I wonder if the problem lies on the way I send the bits over spi.xfer2 or some other configuration that could be missing.
Oscilloscope images when sending spi.xfer2([1,254]), maybe it can help. I cannot understand the issue yet.
Here I am using a slower clk than the maximum 10.5MHz specified in the datasheet.
CS and SCLK:
MOSI and SCLK:
MISO and SCLK:
And these are the signals at input (1) and output (2). This gain never changes when set to SPI mode:
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