Author Topic: Controlling SQM-LU with an Arduino/compatible  (Read 215 times)


  • Anthony Tekatch
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Controlling SQM-LU with an Arduino/compatible
« on: March 24, 2019, 10:59:24 pm »
Here is an example of connecting the SQM-LU (or SQM-LU-DL) to an Arduino compatible single board computer.

The Arduino compatible computer I used was the Teensy 3.2 which is availabke for about $19.80USD.

A USB host interface is required that the SQM-LU can be plugged into. I used the USB Host Shield V2.0 mini for about $4.85USD available from here:

The USB Host shield 2.0 is documented here:

The software library is located here:

Here is the schematic (PDF):

Here is the wiring diagram:

This is the code that I used:
Code: [Select]
#include <cdcftdi.h>
#include <usbhub.h>

#include "pgmstrings.h"

// Satisfy the IDE, which needs to see the include statment in the ino too.
#ifdef dobogusinclude
#include <spi4teensy3.h>
#include <SPI.h>

class FTDIAsync : public FTDIAsyncOper
    uint8_t OnInit(FTDI *pftdi);

uint8_t FTDIAsync::OnInit(FTDI *pftdi)
    uint8_t rcode = 0;

    rcode = pftdi->SetBaudRate(115200);

    if (rcode)
        ErrorMessage<uint8_t>(PSTR("SetBaudRate"), rcode);
        return rcode;
    rcode = pftdi->SetFlowControl(FTDI_SIO_DISABLE_FLOW_CTRL);

    if (rcode)
        ErrorMessage<uint8_t>(PSTR("SetFlowControl"), rcode);

    return rcode;

USB              Usb;
//USBHub         Hub(&Usb);
FTDIAsync        FtdiAsync;
FTDI             Ftdi(&Usb, &FtdiAsync);

void setup() {
  Serial.begin( 115200 );
  #if !defined(__MIPSEL__)
    while (!Serial); // Wait for serial port to connect - used on Leonardo, Teensy and other boards with built-in USB CDC serial connection

  Serial.println("USB Host starting up...");

  if (Usb.Init() == -1)
      Serial.println("OSC did not start.");
void loop()

    if( Usb.getUsbTaskState() == USB_STATE_RUNNING ) {
        uint8_t  rcode;
        char strbuf[] = "rx\r";
        rcode = Ftdi.SndData(strlen(strbuf), (uint8_t*)strbuf);
        if (rcode){
                  ErrorMessage<uint8_t>(PSTR("SndData"), rcode);
        delay(1000); //Wait a while for SQM to respond.
        uint8_t  buf[64];
        for (uint8_t i=0; i<64; i++)
            buf[i] = 0;
        uint16_t rcvd = 64;
        rcode = Ftdi.RcvData(&rcvd, buf);
              if (rcode && rcode != hrNAK)
            ErrorMessage<uint8_t>(PSTR("Ret"), rcode);
              if (rcvd > 2)

This is the output on the Arduino serial monitor:
Code: [Select]
USB Host starting up...
r, 09.37m,0000015912Hz,0000000000c,0000000.000s, 020.6C,D
r, 09.37m,0000015909Hz,0000000000c,0000000.000s, 020.6C,D
r, 09.37m,0000015909Hz,0000000000c,0000000.000s, 020.6C,D
r, 09.37m,0000015909Hz,0000000000c,0000000.000s, 020.6C,D

Some interesting troubleshooting notes are here: