SDI-12 Library

That example goes through the list of available address to see if a sensor is attached that has a corresponding address, so it definitely takes awhile to go through the whole list.  You could rewrite it to only go through the addresses of your sensors and not the entire list.  But your sensors have a 600ms sample time (as stated in the datasheet), so you’ll need to add a little delay after that and then you’ll have the poll time, so I’d allow 1 second for each sensor, and with 8 sensors it’ll take 8 seconds total.  Is that acceptable?

That demo sketch is just a sample of how to talk to your sensors, there’s lots of stuff in there that you could trim out if you’re actually trying to collect data at a certain rate.  What type of board are you using?  Are you planning to store the data on a memory card or just print to the computer’s serial monitor?  There’s a 10-second delay on the very last line of the sketch that isn’t needed if you’re trying to cut down on time between samples.  Do you want to take one discrete reading from each sensor each time, or are you interested in taking several readings from each sensor an averaging them to limit the “noise” or variation between readings of each sensor?   Are you sensors going to be powered continuously or do you want to turn them off between readings?  Do you need a timestamp to go along with each data record?

Is your goal to read all of your sensors and write to your SD card as fast as you possibly can?  You could get faster readings by using concurrent sampling on the Decagons like this:  https://github.com/EnviroDIY/Arduino-SDI-12/blob/master/examples/k_concurrent_logger/k_concurrent_logger.ino

Re-Wrote for you.  I didn’t even test if it compiles, but this should get you going with concurrent measurements:

Delete lines 112-117 of the code I posted.

My intent was to help you by giving you an example of something you could modify to your needs, not to give you a final working program.

This version will compile.  I don’t know if it will actually work for your sensors or log data as expected.  You will need to test that.

Has anyone looked to see if the SDI-12 library could be ported to the new RP2040 chip. Maybe that already works in its existing state, but I haven’t see it mentioned anywhere. This is the new IC that runs the RPi Pico and can be used via the Arduino language.

@vogelrnws I had been looking at porting it to another processor and been using it and digging into the code. I’ve looked at some of the RP2040, but I’m cautious about its ability to go into low power – but haven’t looked at it in depth.

The SDI-12 lib uses a software based UART – running at 1200Baud, so 1200Baud is pretty slow and it does handle it. It needs to have a timer generated to be able to look for the changes in the data stream.

Unfortunately, IMHO, I’ve found it to be quite fragile.   Also the software timing has made debugging fragile.  In 2021 I had also found it worked with some Insitu LT500 sensors and not others. I tried to put a “test station” together, against a traceable SDI-12 test setup using https://www.vegetronix.com/Products/SDI-12 and it failed on the basic physical test.

So I’m thinking about how to 1) +5V buffer  possibly this solution https://github.com/EnviroDIY/Arduino-SDI-12/issues/87

2) hardware timing. Possibly emulate the UART with with either DMA or Timer/Capture.

So maybe the hardware interface could be done with a simple 4 wire Seeed plugin with an off-board buffer and boost to +12V, and software modified.

So just IMHO a heads up on some of the possible issues to consider.

Could you please look at porting the code to the new Arduino R4 UNOs?  They use a different chip (Renesas RA4M1 (Arm® Cortex®-M4)), and I cannot get SDI-12 code to compile for those board definitions.

Reading the preceding posts, I saw you use a software UART for the communication.  The R4 UNO has 2 hardware UARTS, but another plus is that the built-in softwareSerial library supports customizable parity, stop and data bits.  We were able to configure a couple of new ultrasonic water flow  sensors with UART output available from Mouser and Digikey for around $30 to $60 each.  This promises to be a huge improvement for our remote instruments that always required cleaning the Hall effect flow sensors due to debris clogging them.  Neither has Arduino support yet, but we were able to reverse engineer some of the python code of one of the evaluation kits and get them to work with Arduino R3 and R4 UNOs.  I would be happy to share our research and product links.