Hello,
I'm using the eval board TLV320AIC3120EVM-U to evaluate the codec part. The board has been modified to hold the USB processor in reset, so that I can connect into the I2C and I2S lines directly from my microprocessor.
For now I'm trying to output sampled audio from the microprocessor to the codec, and have the codec play it on a speaker and headphone jack. Once I configure the registers in the codec, I send a sampled 1kHz tone to the codec on the I2S. The output on both the speaker and headphones sounds like a 1kHz tone but quite noisy. Looking at the headphone output on a scope, I see the 1kHz sine wave, but it looks fuzzy (as though someone went over the trace with a thick marker.) There is also an extra background noise on the speaker, but not in the headphone.
The I2S signals look correct in a logic analyzer.
My test code is adapted from the example in section 7.3.12.15 of the datasheet (SLAS653C), modified for my ~8kHz sample frequency and ~2MHz MCLK frequency. Here is how I set up the registers, in the style given in the datasheet:
# select page 0
w 30 00 00
# initiate SW reset
w 30 01 01
#(I put a delay of 1 second here)
# Program and power up PLL: J = 40, D = 0, P = 1, R = 1 --> 80 MHz PLL clock output
w 30 04 03
w 30 06 28
w 30 07 00 00
w 30 05 91
#(I put a delay of 1/10 second here)
# NOTE NDAC = 25, MDAC = 1, DOSR = 400, DAC_fs = 8000 --> CODEC_CLKIN = 80000000
# NDAC is powered up and set to 25
w 30 0B 99
# MDAC is powered up and set to 1
w 30 0C 81
# DOSR = 400
w 30 0D 01 90
# mode is i2s, wordlength is 16, slave mode
w 30 1B 00
# select DAC DSP Processing Block PRB_P6
w 30 3C 06
w 30 00 08 # select page 8
w 30 01 04 # I've also tried w 30 01 00 here
w 30 00 00 # select page 0
# select page 1
w 30 00 01
# Program common-mode voltage 1.35 V
w 30 1F 04
# De-pop settings as per the example
w 30 21 4E
# DAC routed to mixer amplifier
w 30 23 40
# Unmute HPOUT, set gain = 0 db
w 30 28 06
# Unmute Class-D, set gain = 24 dB
w 30 2A 1C
# HPOUT powered up
w 30 1F 84
# Power-up Class-D driver
w 30 20 86
# Enable HPOUT output analog volume, set = -1 dB (?)
w 30 24 92
# Enable Class-D output analog volume, set = -1 dB (?)
w 30 26 92
#(I put a delay of 4 seconds here)
# select page 0
w 30 00 00
# Powerup DAC (soft step enabled)
w 30 3F 94
# DAC gain = ?? dB
w 30 41 28
# Unmute DAC
w 30 40 04
#(I put a delay of 1 second here)
Can anyone suggest what might be causing the extra noises?
Thank you.
