higher sample rate

[ChironeX1976]

Hello,
i was wondering how i can get a higher sample rate when reading a sensor. I use a Raspberry Pi with 8 gig RAM. CPU is set at 1200 Mhz. I am using the ADC-device to capture sound, so i need at least 20.000 samples per second.
When i run the by waveshare provided Main.py - TEST_ADC1_RATE at 38400SPS, the output is:

    - ID Read success 
    - REG_MODE2 success
    - REG_REFMUX success
    - REG_MODE0 success
    - REG_MODE1 success
    - SPS-setting: ADS1263_38400SPS
    - ...start and endtime= 1690130018.1033027 1690130018.8256269
    - ...elapsed time for 5000 samples= 0.7223241329193115
    - SPS-result singlechannelfrequency =  6922.100165464822

As you can see, i want 38400 samples per second and i get approx. 7000 samples per second.

Attached, also a plot of 10 seconds of audiosignal-recording. 10 seconds * 38400 SPS should be 384.000 points of data. The horizontal axis shows only 80.000 points.

What am i doing wrong?

Thanks for any advice.

Kris

[mahdiaslanimk]

Roughly the same problem here. @ChironeX1976 did you found any solutions?

[ChironeX1976]

No, i did not find a solution. The program in C is much faster than Python, someone told me, but i did not do any experiments with C. cheerz Kris Op ma 18 dec 2023 om 06:53 schreef Mahdi Aslani ***@***.***>:

…

Roughly the same problem here. @ChironeX1976 <https://github.com/ChironeX1976> did you found any solutions? — Reply to this email directly, view it on GitHub <#15 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ANHCYO5FVJWCMS3EVGSSODLYJ7K6XAVCNFSM6AAAAAA2UVGH4CVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTQNJZGYYDCOBRGA> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[mahdiaslanimk]

@ChironeX1976 Read the FAQ in this link. There you can find the reason of low sps and an example code with higher rate (in both c an python). Hope this helps.

[E-wallace0001]

I have just had a look at the c implementation on the pi zero2 W

Firstly, there are some optimizations you can do for the SPI communications; You can request multiple bytes from the lower level librarys, instead of going back and forth asking for each byte at a time. This will gain you approx 1KHz straight off.

Secondly, the clock is set to 1MHz, changing this will get you a much higher sampling rate. The clocks are hardcoded. BCM driver needs to set a clock divider, while the wiringpi, and dev lib need to be set. My clock seems to top out at 22MHz. This can be configured in /lib/config/dev_config.c under DEV_module_init.

With the above changes, 35KHz can be achieved with wiring pi.

I was a little bit surprised that not requesting the status bytes actually slowed down the sampling rate.

I feel a better interface to the underlying libraries would be beneficial.

Hope this helps.

[brendanwallison]

Hello, I was looking at buying this ADC for audio as well. I have a very basic question about the 38400 SPS. If you plug in multiple microphones, would the sample rate be divided by the number of microphones, or is this a per-channel figure?

[schwebke]

on my Raspberry Pi Zero 2 W I was able to speed up the python solution from 6.275 SPS to 20.500 SPS -- in case someone wants to give it try for more testing:
https://github.com/schwebke/High-Pricision_AD_HAT

[bibhu223]

Did anyone use Pi 5 for this ADC ? I am not able to run this with C as well as python .. because it doesn't have bcm2835 ...can anyone help me.

[mahdiaslanimk]

@bibhu223 to use the python library for RPi 5 do the following:

• install rpi-lgpio library

pip install rpi-lgpio

• delete the implementation condition at the end of the config.py file and force it to use RPi:

#if hostname == "raspberrypi":
#    implementation = RaspberryPi()
#else:
#    implementation = JetsonNano()

implementation = RaspberryPi()

• run main.py (first cd to the folder containing this file)

Python3 main.py

[bibhu223]

I have already tried this way ,, but it's showing error
Runtime error : Cannot determine SOC peripheral bas address

[bibhu223]

@mahdiaslanimk Thank you ,, i reboot the system now it's working on python ,, but it's very slow SPS , I was using pi zero W , In C the speed was very good .. but in this case 4kHz in single channel maximum .. How to increase the speed , One more thing the sample rate is not consistent , in my python program I am using some software smoothing and filtering ,which requires constant sampling rate ..but during data acquisition the sample is fluctuating...how to deal with this .

[bibhu223]

@ChironeX1976 , Have you tried with raspberry pi 5 with C , I am not able to run on C with pi 5 .

[mahdiaslanimk]

@bibhu223 have you enabled SPI interface in the config:
sudo raspi-config

[bibhu223]

@mahdiaslanimk
n@raspberrypi:~/adc/hat/c $ sudo ./main
ADS1263 Demo
/***********************************/
Current environment: Debian
Please make JETSON !!!!!!!!!!
Segmentation fault
...This is error I am getting

[bibhu223]

@mahdiaslanimk yes it's running on python.
But the above issue is coming when I run in C . As I need little bit higher data rate ....so I was trying with C . But not able to run.

[mahdiaslanimk]

@bibhu223 i didn’t try the C codes. Have you tried @E-wallace0001 ‘s suggestions or @schwebke ’s codes to speed up data acquisition using python?

[bibhu223]

@mahdiaslanimk yes , but still if I am plotting the voltage data in real time ...the frequency of data rate is only 40-60Hz ,,