AFE7920: Buggy AGC/ALC initialization

Hi Christian,

Yes, I have observed similar recently as well. You can either call agcAlcConfiguration() after the bringup or you can add this code after AFE.deviceBringup() to properly set the paramters in the AFE:

AFE.deviceBringup()
CAFE.closeAllPages(0)

## LNA bypass setup
for ch in range(4):
    if sysParams.agcParams[ch].lnaEn:
		#info(sysParams.agcParams[ch].lnagain0)
		val = sysParams.agcParams[ch].lnagain0			# LNA bypass value 
		device.writeReg(0x12, 0x1<<ch)                  # open RX_TOP page
		device.writeReg(0x4BC, (val&0xff))              # lnagain0[7:0]
		device.writeReg(0x4BD, ((val >> 8) &0x7))       # lnagain0[10:8]
		device.writeReg(0x12,0)                         # close RX_TOP page

The lnaGain0 param (which specifies how much the DSA should increase once LNA is bypassed) is bugged and not set correctly, and is by default set to 0. Then, when the LNA is bypassed, the AFE reduces the DSA by lnaGain0, which it thinks is 0, so this looks like the LNA bypass is not working.

You can use the above code to directly set the lnaGain0 parameter in the correct register. Note that lnaGain0 has a resolution of 1/32 dB, so set lnaGain0 to be 32 times your LNA gain. For example, for a 15 dB LNA, set lnaGain0 = 480.

Thanks!

Aman