This RTL module interfaces with the Linear Tech LTC6912-1 programmable gain amplifier and LTC1407A-1 dual 14-bit ADC converter available on the Spartan 3-AN Starter Kit. It is essentially a minimal SPI core that both programs the amplifier and interfaces with the ADC for continuous capture.
Interfacing with this module is very simple. Hook up all of the appropriate signals (see the comments in the file) and control it as follows.
-
Start by providing a reset pulse of some duration. I found that 64 clock cycles at 50MHz worked well. If you don't, the pre-amp hardware doesn't settle correctly.
-
When you are ready to program the gain, load the pre-amp gain into the
gain
bus, and then pulseamp_cfg
for one clock cycle. -
Wait for
amp_done
to go high. Now you can begin sending ADC conversion requests. -
To retrieve a sample from the ADC, pulse
start_conv
for one clock cycle and wait foradc_done
to go high. At this point, the signalsadc_a
andadc_b
will be valid until the next conversion request.