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Questions about AD5560 SPI and voltage forcing

Question asked by Aiden on Mar 16, 2018
Latest reply on Mar 20, 2018 by Aiden

Hi,

I've met problems on using AD5560 with Arduino.

1.My force pin output give ground value after I set the DAC.

2.My register SPI readback doesn't match desired value.

 

Only basic functioning pins were connected: SPI, power and grounds, force&sense with load applied. Circuit was driven with +-12V AVDD/AVSS, +5V DVCC, +3.3V VREF. My plan is to test its basic force & sense function, and applied the code following:

 

digitalPotWrite(0x0B,0x0000);
digitalPotWrite(0x08,0x2D69);

 

where

void digitalPotWrite(uint8_t address, uint16_t value) {
SPI.beginTransaction(SPISettings(1000,MSBFIRST,SPI_MODE0));
digitalWrite(slaveSelectPin, LOW);
uint8_t valueMSB= (value >>8);
uint8_t valueLSB= value & 0xFF;
delay(100);
//Transfer:Register address & value in write mode. Receive: useless data
SPI.transfer(address);
SPI.transfer(valueMSB);
SPI.transfer(valueLSB);
digitalWrite(slaveSelectPin, HIGH);
delay(1000);
digitalWrite(slaveSelectPin, LOW);
//Transfer:Register address & value in read mode. Receive: useless data
SPI.transfer(address|0x80);
SPI.transfer(0x0);
SPI.transfer(0x0);
digitalWrite(slaveSelectPin, HIGH);
delay(1000);
digitalWrite(slaveSelectPin, LOW);
//Transfer:NOP in write mode. Receive: Register data
SPI.transfer(0x0);
SPI.transfer(0x0);
SPI.transfer(0x0);
digitalWrite(slaveSelectPin, HIGH);
delay(1000);
SPI.endTransaction();
}

 

We expected the voltage output from FINDAC would be around +2V, but our reading was always 0. Same applies to other input value. Seems the device give no response after register value was written. Could you give me some ideas about this?

 

I observed the sent & received waveform as follows:

Send:

Receiving:

For all R/W I've tried, the received bit 15 & 7 were always pulled high. How's that happening?

I'm new to this so if my explanationmake you confused, do let me know as I'll reply asap.

Thank you for your help!

 

Sincerely,

Aiden

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