Dude about code for DAC7750 with the same electrical schematic on page 38 of the data sheet.

Emanuel Laudonio

Hello support/comunity

I make a board with the example electrical schema 8.2.1 (Analog output Module for PLC-and DCS Based Industrial -Control Systems) page 38 the only difference between this one an the one that I make is a pull down resistor on pin 7 on the ISO7631 that control the enable of SDO communication pin because we have another device on this bus, so here is dude my partner Nicolas is working with the code and make the following code cited below.

The code write 0x00FF, and the DAC answer with high level for an short period on the SDO pin without any clock and then return 0x00F0, the current output still in 0.

Could you please help us to find what is wrong here, in this code or show us an example if you have it?

Thanks in advance

PHY_INA = 0; // TO CLEAR

PHY_INB = 0; // TO LATCH

fdac_write((uint8_t)DAC_WRITE_DAC,(uint16_t)0x00FF);

toReturn = fdac_read((uint8_t)DAC_RD_DAC);

#define DAC_NOP 0x00

#define DAC_WRITE_DAC 0x01

#define DAC_READ 0x02

#define DAC_WRITE_CTRL 0x55

#define DAC_WRITE_RST 0x56

#define DAC_WRITE_CFG 0x57

#define DAC_WRITE_GAIN 0x58

#define DAC_WRITE_ZERO 0x59

#define DAC_WTDG_RST 0x95

#define DAC_RD_STATUS 0x00

#define DAC_RD_DAC 0x01

#define DAC_RD_CTRL 0x02

#define DAC_RD_CFG 0x0B

#define DAC_RD_GAIN 0x13

#define DAC_RD_ZERO 0x17

//For write the DAC

void fdac_write(uint8_t address, uint16_t value)

{

volatile uint8_t tmpRFIE = RFIE;

uint8_t aux;

uint16_t toReturn;

RFIE = 0;

PHY_INB = 0; // TO LATCH

PHY_CS2 = 1; // ISO7631 ENABLE

SPIPut(address);

SPIPut(value >> 8);

SPIPut(value);

PHY_INB = 1;

NOP();

PHY_INB = 0;

PHY_CS2 = 0;

RFIE = tmpRFIE;

}

//for read the DAC

uint16_t fdac_read(uint8_t address)

{

volatile uint8_t tmpRFIE = RFIE;

uint8_t aux;

uint16_t toReturn;

RFIE = 0;

PHY_INB = 0;

PHY_CS2 = 1;

SPIPut((uint8_t)DAC_READ);

SPIPut(0x00);

SPIPut(address);

PHY_INB = 1;

NOP();NOP();NOP();NOP();

PHY_INB = 0;

aux = SPIGet();

toReturn = aux << 8;

aux = SPIGet();

toReturn = toReturn + aux;

PHY_INB = 1;

NOP();

PHY_INB = 0;

PHY_CS2 = 0;

RFIE = tmpRFIE;

return toReturn;

}

over 8 years ago

0 Kevin Duke over 8 years ago

TI__Mastermind 46290 points

Hello,

In order to assist you it would be helpful if you could share a schematic. While I understand that it is designed to mimic the schematic shown in the datasheet, for completeness sake it would be good to review. If you're not comfortable with sharing your schematic on the forum we can exchange that through a private message.

Providing a code review is a little outside of my core competencies, I'm also not sure what platform this code is written for so I'm not able to extrapolate much. It would be easiest if you could provide oscilloscope captures of the SPI interface (SCLK, SPI, SDO, and LATCH) such that I can examine the timing.

We have a small code example for the MSP430 platform: 4314.DAC8760_Interface.zip

0 Emanuel Laudonio over 8 years ago in reply to Kevin Duke

Prodigy 210 points

I think the error is on control register, the frame should be at least xx01xxxxxxx00101 for 4 20mA

0 Kevin Duke over 8 years ago in reply to Emanuel Laudonio

TI__Mastermind 46290 points

Emanuel,

I'm not sure what the context of this post is, but the 16-bit data word you've shared is valid for configuring the output range to 4-20mA mode and enabling the output.

0 Kevin Duke over 8 years ago in reply to Kevin Duke

TI__Mastermind 46290 points

This thread was taken to private message, and solved there.

0 Emanuel Laudonio over 8 years ago in reply to Kevin Duke

Prodigy 210 points

At very first point the frame was wrong my partner forgot turn on the output xx01xxxxxxx00101 after read the data sheet and asked you this was solved then forgot the Chip select 2 (we have more than one peripheral connected) after that at the end and in the worst case my partner forgot turn on the power supply (when all was ok the power supply was powered off).

Best Regards

Data converters

Data converters forum

Dude about code for DAC7750 with the same electrical schematic on page 38 of the data sheet.