Bypassing SDI-12 library to read 8-bits by using high volume binary command

I’m working with soil moisture sensors and currently using the Acclima TDR-305N, which communicates via the SDI-12 protocol. I’ve successfully interfaced with the sensor using the Arduino SDI-12 library and can retrieve standard measurements without issue.

However, I’m now trying to access the actual TDR waveform using the High Volume Binary Command described in the SDI-12 v1.4 specification (Section 5.2, <a class=”relative pointer-events-auto a cursor-pointer

underline
” href=”https://sdi-12.org/current_specification/SDI-12_version-1_4-Jan-30-2021.pdf&#8221; target=”_blank” rel=”noopener nofollow noreferrer ugc”>https://sdi-12.org/current_specification/SDI-12_version-1_4-Jan-30-2021.pdf). This command transmits data in 8-bit binary format, which breaks out of the standard SDI-12 framing (normally 7 data bits + 1 parity bit).

Here’s the issue: when I send the command using the SDI-12 library, I only receive 7 bits per byte — the 8th bit is consistently missing. I suspect this is because the library is still enforcing SDI-12 framing, even though the binary data should be handled differently.

Has anyone successfully bypassed the SDI-12 library to capture all 8 bits of binary data? My sensor SDI-12 address is 3.

// Command 1: Start waveform measurement (3HB!)
myCommand = String(SENSOR_ADDRESS) + “HB!”;
Serial.println(myCommand);
mySDI12.sendCommand(myCommand);
delay(30); // Wait for a response

sdiResponse = “”;
while (mySDI12.available()) {
char c = mySDI12.read();
if ((c != ‘\n’) && (c != ‘\r’)) {
sdiResponse += c;
delay(10);  // 1 character ~ 7.5ms
}
}
if (sdiResponse.length() > 1) {
Serial.println(sdiResponse);
}
mySDI12.clearBuffer();
delay(1000);

// Command 2: Request first block of waveform data (3DB1!)
myCommand = String(SENSOR_ADDRESS) + “DB0!”;
Serial.println(myCommand);
//Serial1.println(myCommand);
mySDI12.sendCommand(myCommand);
delay(30);
int count;
count = 0;
while (mySDI12.available()) {
char c = mySDI12.read();
count = count + 1;
for (int i = 7; i >= 0; i–) {
Serial.print(bitRead(c, i));
}
Serial.print(“\t”);
if (count % 2 == 0) {
Serial.println();
}

if ((c != ‘\n’) && (c != ‘\r’)) {
sdiResponse += c;
delay(8);
}

}