Concept Design

[ivconic]

from 2400 SPS up to 19,200 SPS
Sorry but much too slow for direct sampling

Yes I overlooked that!
Dang!
I'm on the Mouser and Analog Devices pages right now... using the "filtered" search engine, looking for specs that meet the criteria.
Hmmm... this is my first time doing this with details. And I'm very surprised that there is actually no such ADC that meets the top criteria!
And that would be:
1) 24-bit
2) At least 4 and preferably 8 channels
3) Not below 500ksps
4) "Simple and easy" connection means; no parallel, only and exclusively serial. Preferably SPI.
5) Sigma-Delta or SAR
6) Voltages not bellow 3v3
...
No such one on those sites...

[ivconic]

Here, I listed roughly 6 criteria. If I were to throw out even one; something would be found.
But what tradeoff can be accepted here?
Carl convinced me that 2 channels were insufficient, 4 would get the job done and 8 is preferable.
24-bit is somehow the "holy grail"... 16-bit is a much easier criterion. 18-bit can be found with another tradeoff along.
Connection... serial is the only one that fits. And to be as fast as possible.
Power supply... is not an insignificant item.
Things would be much simpler if all voltages were in the range of 5v, but there are none, so 3v3 is also acceptable.
Anything below that will require additional complications around PS.
There is literally no chip that would meet all the listed criteria.
What is the "harm" if you go with 16-bit? Or with 18-bit?
There are better chances to find a chip with these resolutions.

[ivconic]

1. ADS1256: This is a 24-bit ADC with 8 channels and a maximum sample rate of 8 million samples per second (MSPS). It supports SPI communication.
2. LTC2440: This is a 24-bit ADC with 8 channels and a maximum sample rate of 1.8 MSPS. It supports SPI communication.
3. ADS1115: This is a 16-bit ADC with 4 channels and a maximum sample rate of 860 samples per second. It supports I2C and SPI communication.
4. MCP3551: This is a 24-bit ADC with 1 channel and a maximum sample rate of 500 kSPS. It supports SPI communication.

[ivconic]

That's wha I got asking https://chat.openai.com/chat

[ivconic]

After 12-th attempt I got more/less simillar lists. So...

[Willy Bayot]

1. ADS1256: 30kSPS
2. LTC2440: Up to 3.5kHz Output Rate .
3. ADS1115: • Programmable Data Rate: 8 SPS to 860 SPS
4. MCP3551: conversion time 73msec.

[Willy Bayot]

Carl convinced me that 2 channels were insufficient, 4 would get the job done and 8 is preferable.
.

One channel is sufficient for DIRE CT SAMPLING

[ivconic]

That's what I got at https://chat.openai.com/chat
Obviously it is not that smart...

[Willy Bayot]

SUGGESTED Modular Architecture

• PSU board
  • Analog +5V,-5V,
  • Digital +3V
  • MOSFET drivers 15V
  • Adjustable XMIT Voltage 1 to 3V
• XMIT Board CC circuit (+ compensation)
• Processing platform (NUCLEO)
  • Daughter board (ARDUINO connectors) with RECEIVE Circuits and external ADC
  • Timing
  • DSP
  • HIM board
    • Simple Display interface ( HD44780 20×4 LCD)
    • few LED's and push buttons or joystick
    • SD Card storage
      • Signal data logging
      • System Parameters
  • Serial Debug Control & Logging

[ivconic]

[waltr]

1. ADS1256: This is a 24-bit ADC with 8 channels and a maximum sample rate of 8 million samples per second (MSPS). It supports SPI communication.
2. LTC2440: This is a 24-bit ADC with 8 channels and a maximum sample rate of 1.8 MSPS. It supports SPI communication.
3. ADS1115: This is a 16-bit ADC with 4 channels and a maximum sample rate of 860 samples per second. It supports I2C and SPI communication.
4. MCP3551: This is a 24-bit ADC with 1 channel and a maximum sample rate of 500 kSPS. It supports SPI communication.

Need to go back to what Carl said about why he desired a mulit-channel ADC.
What I remember is this multi-channel can be slower.

So maybe use one (or two) high speed (1-2Msps) and deep 18-24bit, for direct sampling.
Then add another multi-channel ADC for those other tasks.

[Willy Bayot]

Need to go back to what Carl said about why he desired a mulit-channel ADC.
What I remember is this multi-channel can be slower.

So maybe use one (or two) high speed (1-2Msps) and deep 18-24bit, for direct sampling.
Then add another multi-channel ADC for those other tasks.

We just need a single channel with high conversion rate.
All the other tasks may be executed from the internal 12-bit ADC

[Carl-NC]

That's wha I got asking https://chat.openai.com/chat

Already I'm not impressed, ChatGPT apparently didn't bother to read the data sheets. The ADS1256 is only 30kSps. The results I got were:

ChatGPT is at capacity right now

There are 2 potential paths. Direct sampling will require a 16+ bit fast (100K-1MSps) single-channel ADC. Analog demods require a slower ADC (1kSps or so) but with up to 8 preferably simultaneous-sampling channels. Right now I am looking only at direct sampling but will leave in hooks for analog demods.

[ivconic]

Direct sampling is also interesting to me.
But ... we need a good ADC and probably an even better mcu...
Maybe it's time to finally set a clear concept, "that ... that... that and that..." and period.
I personally am not in a situation where I can easily acquire such material.
But I have an idea!
One or more of you, who are in a more favorable situation; you can project and prepare the pcb with ADC and mcu and everything else that is needed,
send it to JLPcb for production (including the pcb assembly option) and later send it to us who are not in a situation to easily acquire the material.
Of course, with us covering the unnecessary expenses.
Maybe it's better to go for such an option right away than to have everyone mess with different development systems, different ADCs, etc.
What do we need for direct sampling?
Very few components.
RX frontend, ADC, MCU, TX driver, audio output and user interface pins (buttons, LCDs...).
in JLPcb let them assemble only small SMD components and we will complete all the others ourselves later.
The cost for such a pcb should not be high. Just accessible to the vast majority of hobbyists on the forum.

[ivconic]

"...Of course, with us covering the unnecessary expenses..."


Of course, with us covering the necessary expenses!