Author Topic: pcm1808 not putting out data  (Read 1497 times)

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Offline gcrcienTopic starter

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pcm1808 not putting out data
« on: October 29, 2025, 06:02:51 pm »
Hello, im working on a diy SDR using basic audio gear.
In the prototipe tests I had already figured out how to do the data aquisition using a simple pcm1808 sampling baseband upt to 200ks/S.
However the pcb has arrived from jlcpcb and the ADC seems not responsive, i have already checked every signal going into the ADC and they seem to be ok.
What can cause a pcm1808 to not put out data?
I2S Signals going from the esp32 configured at 48ks/S to the pcm1808 are these:
scki pin-6 12.288mhz
lrck pin-7 48khz
bck pin-8 3.072mhz
*edit:Corrected this
All clocks seem to be healthy.
I have checked with known good ADC's, one thing i have not measured is the phase alignment on these clocks but there's not any significant jitter that i can see
« Last Edit: October 29, 2025, 07:41:56 pm by gcrcien »
 

Offline SiliconWizard

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Re: pcm1808 not putting out data
« Reply #1 on: October 29, 2025, 06:42:44 pm »
It's not fully clear how you had prototyped this. Did you maybe use PCM1808  breakout boards?
One thing to check is whether the MD0/MD1 pins are properly configured.

Another thing I just noticed is that you mentioned "BCK pin 48 kHz". Surely this is a mistake here. This is the bit clock and should typically be 64 times the sample rate (as there are 64 data bits in an I2S stereo frame).
Looks like you may have reversed LRCK and BCK? Maybe the mistake is in your post and not on your board though.
 

Offline gcrcienTopic starter

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Re: pcm1808 not putting out data
« Reply #2 on: October 29, 2025, 07:36:45 pm »
You're right, i just rechecked my notes and its backwards, i just swapped the pins when writing the post.
pin 6 SCKI 12.288mhz
pin 7 LRCK 48khz
pin 8 BCK 3.072mhz(64X sampling freq)
The original test board was made with toner transfer method and an external adc module.
The pic with the waterfall graph is using that board
pins md0 and md1 and fmt are tied to ground to use slave mode and i2s 24bit as per the datasheet

 

Offline gcrcienTopic starter

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Re: pcm1808 not putting out data
« Reply #3 on: October 29, 2025, 08:55:11 pm »
Well that was dumb, there was a short to ground on the pcm1808 dout pin, it was so low impedance that i was never able to measure anything there, i remember that i had measure this the first time but surely i was wrong.
Now to work on the software for this thing
 

Offline gcrcienTopic starter

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Re: pcm1808 not putting out data
« Reply #4 on: November 01, 2025, 04:53:37 pm »
Working!! :-+
 


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