Hi Dan,
We are finally sampling properly but the sampling rate seems to be very low. We are seeing 21k samples in 5 seconds worth of data but it should be almost 1 million samples in that time. Am I missing something?
Well a lot of things that I don't know about how you are sampling the data?
1 - Are you using my original version in folder ./picoADC_USB?
Like I said if you modify the SAMPLE_CHUNK_SIZE and SAMPLE_CHUNK_SIZE and set them to 12 and 24 well you reduce the transfer rate about 10 folds. Bigger the chunk last handling between packet!
2- The USB speed transfer by itself!
There is a maximum speed transfer from the USB serial rate. I found out that the PI5 is slower on USB serial transfer than the Pi4.
3- And of course the storage device you are using . If it is a "Pi" than a fast SD card is needed.
Each packet contains timestamp . Check if you are missing some by comparing timestamp!
Modify the "usbtodisk.py" to save nothing but check the timestamp only. This will give you an indice about the transfer rate without saving it.
B.T.W. For all the test I did the best way was the method to save on SDcard using the SDIO mode.
A way to test the data is to store the incoming USB serial port data to ramdisk .
copy everything from the USB serial to a file on the ramdisk.
ex: create a 250 MB ramdisk on rasberry Pi
Code:
daniel@Pi5:~ $ sudo mkdir /ramdiskdaniel@Pi5:~ $ sudo chmod 777 /ramdiskdaniel@Pi5:~ $ sudo mount -t tmpfs -o size=250m aramdisk /ramdiskdaniel@Pi5:~ $ df -hFilesystem Size Used Avail Use% Mounted onudev 3.8G 0 3.8G 0% /devtmpfs 805M 6.0M 799M 1% /run/dev/sda2 29G 12G 16G 43% /tmpfs 4.0G 432K 4.0G 1% /dev/shmtmpfs 5.0M 48K 5.0M 1% /run/lock/dev/sda1 510M 75M 436M 15% /boot/firmwaretmpfs 805M 144K 805M 1% /run/user/1000aramdisk 250M 0 250M 0% /ramdiskdaniel@Pi5:~ $Just transfer everything from the USB port to a file in the ramdisk folder
Code:
cat /dev/ttyACM0 >/ramdisk/capture1.txtNow analyze what you have on /ramdisk/capture1.txt.
This way you exclude the speed needed for the python script to decode the serial input and the transfer to store to the SDCard.
Statistics: Posted by danjperron — Tue Feb 20, 2024 8:14 pm