LTC1760CFW I2C comms with arduino

Question

Pages 15 and 16 of the LTC1760 datasheet show a breakdown of the I2C comms. This looks pretty clear, but I must be interpreting it incorrectly. I can see there is a device on node 0x0A (surprisingly not 0x14, 0x16, or 0x18 as shown in the chart), but my attempts to send a command are not instigating reply data. 
 In a nutshell, I am attempting 
 Wire.begin(8); //join with address of 8 
 Wire.beginTransmission(0x0A); //send info to address A 
 Wire.write(0x04); //send command code 4 for BatterySystemInfo() 
 ackCheck=Wire.endTransmission(); //verify Ack of address 
 When monitoring the address afterwards, I see no reply, whereas I am expecting two bytes. 
 Would someone be willing to explain if the layout of the command is more than sending a byte to the appropriate address. Is the layout of the response more than two bytes? 
 Thanks!

ADIApproved · Accepted Answer

Hi Dan, The problem may be that the LTC1760 needs an actual repeated start bit. The endTransmission() function, with no argument, does a stop and then a start which will not work here. Below is some working sample code that will repeatedly read this register. Let me know if you still have any trouble. ----------------------------------------------------------------------- #include void setup() { Wire.begin(); Serial.begin(9600); } uint8_t address = 0x0A; // 0x14, but Wire i2c adressing uses the high 7 bits so shift right uint8_t reg = 0x04; // BatterySystemInfo() register uint8_t numBtyes = 2; void loop() { Wire.beginTransmission(address); Wire.write(byte(reg)); // sets register pointer Wire.endTransmission(false); // repeated start Wire.requestFrom(address, numBtyes); // request 2 bytes from slave device #112 int reading = 0; if (Wire.available() >= numBtyes) { reading = Wire.read(); // receive low byte reading |= Wire.read() << 8; // receive high byte printHex(reading, 4); } else // nothing was received { Serial.println("Nothing Received"); } delay(1000); } void printHex(int num, int precision) { char tmp[16]; char format[128]; sprintf(format, "0x%%.%dX", precision); sprintf(tmp, format, num); Serial.println(tmp); } ----------------------------------------------------------------------- Regards, Zack)

ADIApproved · Answer

Hi Dan, 
 The BatterySystemInfo() register is read-only. You are trying to read it, correct? 
 I believe your understanding of the command layout is correct. Yes, the register is two bytes. I think what you are missing is that you need to prompt the read by using a read command. 
 The Arduino Wire library allows you to do this. I think the most helpful example may be this one because it shows how to set the register pointer value and then request data, which is what you will need to do here: 
 Arduino - SFRRangerReader 
 For general reading commands, this is a good place to start: 
 Arduino - WireRead 
 Let me know if you need any further information. 
 Regards, 
 Zack

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LTC1760CFW I2C comms with arduino