blackfin

[kelly k]

Description: I designed a small board with an AD7716 ADC for biomedical application. The board is designed as per ADSP -2101 example in the AD7716 datasheet. The board connects directly to the sport 0 interface on the Blackfin ADSP BF537 EZ-Kit Lite board. I managed to get a small program working which programs the AD7716 with filter cutoff frequencies and then sets it to master mode. I have been unsuccesful however in reading data rom the device. I set the device in master mode and it streams four channels 32 bits of data in 4 byte chunks. I can not read them in on the blackfin rx line. I have done this in C but would prefer to do it all in labview, I have embedded module 2.5 and labview 8.6. Can someone assist in telling me what parameters are required to be set for the sport configuration. Also if possible if someone could give me a sample vi that would also help. Pins used are as follows : Pin 2: vdd Pin 5: reset -> reset (AD7716) Pin 6&16: PJ9_TSCLK0 tied with PJ6RSCLK0 ->SCLK(AD7716) Pin 7: PJ7_RFS0 ->RFS0 (AD7716) Pin 8&14: PJ8DR0PRI& PJ11DTR0PRI-> SDATA (AD7716) Pin 10: PF10_LED5 -> MODE (AD7716) Pin 11: PJ10_TFS0 -> TFS (AD7716) Pin 18: PF11_LED6 -> DREADY (AD7716) Pin 25: PF6_LED1 -> DIN (AD7716) Pin 28&30&32: LED4&3&2 -> A2&A1&A0 (AD7716) Pin 34 : GND -> GND (AD7716) Platform : ADSP-BF537 EZ-KIT Lite Software : VisualDSP++ 5.0 Data sheet for AD7716 http://search.analog.com/search/default.aspx?local=en&query=AD7716&contentType=Data_Sheets Kudos! Thanks!

[NicB]

There is already a thread started here

You could follow the TWI example described in the link suggestd byTony Gibbs (http://zone.ni.com/devzone/cda/tut/p/id/5861).

How come you don't know the SPORT settings if you had already written a C version?

[kelly k]

Yes believe me i have tried using other examples to get it up and running, which is how i managed to program the board in the first place. Basically i cant use two wire as the board is already designed and hardwired to the primary data line of sport, to use ht etwo wire interface it needs to be connected to sdata. I managed to use the audio talktrough examples with some modification to program it, but i cannon get it to recieve, transmit settings and rx settings are different so not sure what i should be setting for recieve. For instance its says in data sheet to use alternate framing when using adsp 2101 processor but the timing diagrams they suppy to not represent alternate framing, although alternate has worked for transmit mode. I have set device in serial and can see it transmitting data, ive just realised no tere maybe another issue, the data never goes above 1.2v. This could be the reason why im not recieving data in my code. I have an interrupt routine which interrupts when data is recieved in the port but when i access the data its blank.

[NicB]

I didn't say you could use TWI - I just suggested to watch an example about developping the driver over busses protocols.

The graphs from the datasheet are as in alternate/late mode (active low), so you can configure the SPORT either for 8 bit or 32 bit because the frame sync is checked on the first bit only.

[kelly k]

any reason why the output data level never goes above 1.2v , should it not be going to 5v as the datasheet states, -.3v dvdd +.3v?

[NicB]

Probably because you have two masters there (DSP and ADC).

You want the ADC in master mode for some reasons (perhaps just to avoid external interrupts from DRDY).

In this case I would keep the ADC in reset while SPORT is switched from master to slave (after control register configuration trasnmision). You could wire the ADC RESET to one of the LED signals.