How to use multiple VL6180 TOF sensors? - arduino

Question

I am trying to connect two Sparkfun VL6180 TOF sensors to an Arduino board through the I2C bus. I am able to read the data from both sensors individually, but I can't read from both sensors if both are connected to the I2C bus.
I can read the value from a single sensor while both are connected. When I try to find the address of both sensors using an I2C scanner, I can only find one sensor's address, which is the default 0x29. Individually I can read the address of the sensor but both have the same address. Does anybody know how to solve the issue?
The I2C scanner code:
#include <Wire.h>
#include <Arduino.h>
// scans devices from 50 to 800KHz I2C speeds.
// lower than 50 is not possible
// DS3231 RTC works on 800 KHz. TWBR = 2; (?)
long speed[] = {
50, 100, 200, 250, 400, 500, 800
};
const int speeds = sizeof(speed) / sizeof(speed[0]);
// DELAY BETWEEN TESTS
#define RESTORE_LATENCY 5 // for delay between tests of found devices.
bool delayFlag = false;
// MINIMIZE OUTPUT
bool printAll = true;
bool header = true;
// STATE MACHINE
enum states {
STOP, ONCE, CONT, HELP
};
states state = STOP;
uint32_t startScan;
uint32_t stopScan;
void setup() {
Serial.begin(115200);
Wire.begin();
displayHelp();
}
void loop() {
switch (getCommand()) {
case 's':
state = ONCE;
break;
case 'c':
state = CONT;
break;
case 'd':
delayFlag = !delayFlag;
Serial.print(F("<delay="));
Serial.println(delayFlag ? F("5>") : F("0>"));
break;
case 'e':
// eeprom test TODO
break;
case 'h':
header = !header;
Serial.print(F("<header="));
Serial.println(header ? F("yes>") : F("no>"));
break;
case '?':
state = HELP;
break;
case 'p':
printAll = !printAll;
Serial.print(F("<print="));
Serial.println(printAll ? F("all>") : F("found>"));
break;
case 'q':
state = HELP;
break;
default:
break;
}
switch (state) {
case ONCE:
I2Cscan();
state = HELP;
break;
case CONT:
I2Cscan();
delay(1000);
break;
case HELP:
displayHelp();
state = STOP;
break;
case STOP:
break;
default: // ignore all non commands
break;
}
}
char getCommand() {
char c = '\0';
if (Serial.available()) {
c = Serial.read();
}
return c;
}
void displayHelp() {
Serial.println(F("\nArduino I2C Scanner - 0.1.03\n"));
Serial.println(F("\ts = single scan"));
Serial.println(F("\tc = continuous scan - 1 second delay"));
Serial.println(F("\tq = quit continuous scan"));
Serial.println(F("\td = toggle latency delay between successful tests."));
Serial.println(F("\tp = toggle printAll - printFound."));
Serial.println(F("\th = toggle header - noHeader."));
Serial.println(F("\t? = help - this page"));
Serial.println();
}
void I2Cscan() {
startScan = millis();
uint8_t count = 0;
if (header) {
Serial.print(F("TIME\tDEC\tHEX\t"));
for (uint8_t s = 0; s < speeds; s++) {
Serial.print(F("\t"));
Serial.print(speed[s]);
}
Serial.println(F("\t[KHz]"));
for (uint8_t s = 0; s < speeds + 5; s++) {
Serial.print(F("--------"));
}
Serial.println();
}
// TEST
// 0.1.04: tests only address range 8..120
// --------------------------------------------
// Address R/W Bit Description
// 0000 000 0 General call address
// 0000 000 1 START byte
// 0000 001 X CBUS address
// 0000 010 X reserved - different bus format
// 0000 011 X reserved - future purposes
// 0000 1XX X High Speed master code
// 1111 1XX X reserved - future purposes
// 1111 0XX X 10-bit slave addressing
for (uint8_t address = 8; address < 120; address++) {
bool printLine = printAll;
bool found[speeds];
bool fnd = false;
for (uint8_t s = 0; s < speeds ; s++) {
TWBR = (F_CPU / (speed[s] * 1000) - 16) / 2;
Wire.beginTransmission (address);
found[s] = (Wire.endTransmission () == 0);
fnd |= found[s];
// give device 5 millis
if (fnd && delayFlag) delay(RESTORE_LATENCY);
}
if (fnd) count++;
printLine |= fnd;
if (printLine) {
Serial.print(millis());
Serial.print(F("\t"));
Serial.print(address, DEC);
Serial.print(F("\t0x"));
Serial.print(address, HEX);
Serial.print(F("\t"));
for (uint8_t s = 0; s < speeds ; s++) {
Serial.print(F("\t"));
Serial.print(found[s] ? F("V") : F("."));
}
Serial.println();
}
}
stopScan = millis();
if (header) {
Serial.println();
Serial.print(count);
Serial.print(F(" devices found in "));
Serial.print(stopScan - startScan);
Serial.println(F(" milliseconds."));
}
}
Code to read data from both sensors:
#include <Wire.h>
#include <SparkFun_VL6180X.h>
#define VL6180X_ADDRESS1 0x29
#define VL6180X_ADDRESS2 0x30
VL6180xIdentification identification1;
VL6180xIdentification identification2;
VL6180x sensor1(VL6180X_ADDRESS1);
VL6180x sensor2(VL6180X_ADDRESS2);
void setup() {
Serial.begin(115200);
Wire.begin();
delay(100);
sensor1.getIdentification(&identification1); // Retrieve manufacturer info from device memory
printIdentification(&identification1);
sensor2.getIdentification(&identification2); // Retrieve manufacturerinfo from device memory
printIdentification(&identification2);
if (sensor1.VL6180xInit() != 0) {
Serial.println("S1FAILED TO INITALIZE");
};
if (sensor2.VL6180xInit() != 0) {
Serial.println("S2FAILED TO INITALIZE");
};
sensor1.VL6180xDefautSettings();
sensor2.VL6180xDefautSettings();//Load default settings to get started.
delay(1000); // delay 1s
}
void loop() {
Serial.print(" S1 :Distance measured (mm) = ");
Serial.println( sensor1.getDistance() );
Serial.print(" S2 :Distance measured (mm) = ");
Serial.println( sensor2.getDistance() );
delay(500);
};
void printIdentification(struct VL6180xIdentification *temp) {
Serial.print("Model ID = ");
Serial.println(temp->idModel);
Serial.print("Model Rev = ");
Serial.print(temp->idModelRevMajor);
Serial.print(".");
Serial.println(temp->idModelRevMinor);
Serial.print("Module Rev = ");
Serial.print(temp->idModuleRevMajor);
Serial.print(".");
Serial.println(temp->idModuleRevMinor);
Serial.print("Manufacture Date = ");
Serial.print((temp->idDate >> 3) & 0x001F);
Serial.print("/");
Serial.print((temp->idDate >> 8) & 0x000F);
Serial.print("/1");
Serial.print((temp->idDate >> 12) & 0x000F);
Serial.print(" Phase: ");
Serial.println(temp->idDate & 0x0007);
Serial.print("Manufacture Time (s)= ");
Serial.println(temp->idTime * 2);
Serial.println();
Serial.println();
}

Answer 1

If the sensors have the same I2C address, and that address can't be configured, you have a problem, as you can't read from both at the same time.
First look into the possibility to configure the I2C address. Many I2C devices have this option.
If this is not available, what you can do is wire the Vcc pin of the sensor to a digital pin of your Arduino. When you want to read from a sensor, you turn the other sensor off by setting its Vcc digital pin to LOW, and turn on the one you want to read from, by setting its Vcc digital pin to HIGH.
However, depending on the type of sensor, you might have to wait until it is ready. Some sensors take time when they're turned on before they can provide accurate readings.