DSP28335 Interfacing to DAC8760 Module

Mark Anthony Cruz

Other Parts Discussed in Thread: TMS320F28335, ADS8332, DAC8760, DAC161S055

I am having troble interfacing the DAC8760 EVM module to DSP TMS320F28335 module through SPI communication because of the 24bit wide character of the DAC registers. DSP28335 only have 26bit character SPI communication. Later i wanted to make the DSP 28335 operate as master and two slave modules, ADS8332 and DAC8760. ADS8332 DSP28335 Communication already function correctly because of SPI 16bit communication but i wanted to add the DAC module to the embedded system but no luck because of the 24bit character SPI. Any suggestions for the interfacing of the DAC8760 to DSP28335? Thanks

over 8 years ago

0 Mark Labbato over 8 years ago

Guru 30330 points

Mark,

One suggestion is to use the SPI with 8-bit word size. you would just transfer three words for a total of 24 bits.
Another would be to use the McBSP in Clock stop mode (SPI mode)

Either of these would be a possibility.

-Mark

0 Mark Anthony Cruz over 8 years ago in reply to Mark Labbato

Intellectual 600 points

is there anyone who have tried to use spi communication with 3 8bits to DAC8760 and succeed??

0 Frank Ankapong over 8 years ago in reply to Mark Anthony Cruz

TI__Mastermind 28275 points

Hi Mark,

I have interfaced SPI with DAC161S055 which uses a similar 24-bit command frame. As Mark indicated, you transmit the command as 3 8-bit words. This is a high level setup:

1. Set the SPI to transmit 8-bits.

2. Enable FIFO.

3. To transmit the 24-bit data, since the SPI starts transmitting from the MSB, you do some bit manipulation as follows:

I. Transmit the 8-bit address by writing this to SPITXBUF -> Address<<8.

II. Transmit MSB of the 16-bit data by writing this to SPITXBUF -> Data&(0xFF00)

III. Transmit LSB of the 16-bit data by writing this to SPITXBUF -> Data<<8

These commands should be one after the other and since you enabled FIFO, they should be transmitted consecutively.

0 Mark Anthony Cruz over 8 years ago in reply to Frank Ankapong

Intellectual 600 points

i am trying now to use MCBSP, but looks more complicated than SPI, which one is better to use? the 3 - 8bit? or the MCBSP? Anyway thanks Frank for the instructions you suggest

0 Mark Anthony Cruz over 8 years ago in reply to Frank Ankapong

Intellectual 600 points

should i be using the FIFOISR here when using the instruction yo suggested transferring 3 8-bits of data, I am still a beginner for the 24bit SPI communication

0 Frank Ankapong over 8 years ago in reply to Mark Anthony Cruz

TI__Mastermind 28275 points

Mark,

Depends on your application. You can use interrupts or instead poll the Transmit FIFO Status which would read 0 when all words have been transmitted.

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DSP28335 Interfacing to DAC8760 Module