AD75019

Are you shifting data in too fast or too slow? SCLK must be between 20 KHz and 5 MHz.

Are you pulsing the PCLK parallel load after shifting the data in?

Hi andrew, thanks for reply.

Yes, I´m Shifting data at 250 KHz, and after shift all the 256 bits I´m strobing the data with a low pulse at PCLK (width = 10uS)

Mauricio.

Andrew Holme wrote:

PIC

scope

I´m

20 KHz

How are you testing for switch closure? How are you biasing the analogue inputs? Are there any unused analogue pins? The datasheet doesn't say if unused inputs are allowed - you might try high value SIL resistors to GND. What power supplies are you using? Are you observing the correct setup and hold times (t1 & t3) as per the timing diagram on page 3 of the datasheet?

If you change your software to shift more than 256 bits - you should see something coming out of SOUT - might be a useful test.

1.- I´m injecting a square wave at analogue input, and viewing the output with a scope.

2.- from the square wave generator.

3.- there are analog inputs unused but pulled down to ground

4.- It´s a PC ATX 300 Watts power supply.

5.- Setup timings seems to be right.

6.- I did a test software that run my PIC in an endless loop Writing

0x55 and SOUT is always High.

Andrew Holme wrote:

bits

the

OK

What voltage levels w.r.t. ground?

Directly or through resistors? What value?

That's not what I meant. What are the voltages on Vdd, Vss and Vcc relative to DGND.

OK

should

Something's wrong there.

In message , Mauricio writes

I've done this - it was a few years ago and I no longer have access to the PIC code. As I recall there's nothing particularly difficult *but* the input shift register is dynamic and has a minimum clock speed of (just looked it up) 20kHz. Once the switch configuration data is clocked in, it's latched and needs no further concern.

Cheers

--
Keith Wootten

Thanks John.

This is a pretty nice code, but there are some things I don´t undestand. Why must I load 640 zeroes into the shift registers if the Crosspoint only have 256 switches? I can suppose you´re initializating

8 AD75019 connected in cascade, then my question is why only 80 bits per IC? Please comment.

john jard> > I´m trying to drive an AD75019 (16x16 Crosspoint Switch) with a

PIC

scope

I´m

chips

;---------------------------------------------------------------------------

chips

;---------------------------------------------------------------------------

In message , snipped-for-privacy@gmail.com writes

Check that the clock is clocking continuously (at >20kHz) and manually connect the Sin pin to 0V and 5V alternately while looking at Sout. Sout should follow Sin (with a short delay). If it doesn't, you've probably got a duff chip. Make sure the power supply sequences correctly, or use Schottky diodes as suggested in the datasheet.

Cheers

--
Keith Wootten

This is a straight copy of a setup routine for a block of 8 of these chips but shows that sending for say one chip, 80 bits of serial data, 80 clocks, and the final update strobe is perfectly straightforward.

regards john

;---------------------------------------------------------------------------

--------------- DISABLE.THE.MATRIX.CHIPS ;shuts down all the outputs. Stops 'multi-output' self destruct ;sends out 640 '0's (0=disable out/pin.

1=enable it) ;this is a hardware routine only ldw 80 ;640 bits worth of zeroes in one lump wto scrap

local1 ldw 8 ;bit count each byte wto scrap1

local2 matrixdata.low ;force zeroes into chips matrixclock.high matrixclock.low decfsz scrap1,self goto local2 decfsz scrap,self goto local1

matrixupdate.low ;latch the data in to the 8 matrix chips matrixupdate.high RETURN ;having pumped 640 0's pumped out ;---------------------------------------------------------------------------

-----------------

This is a pretty nice code, but there are some things I don´t undestand. Why must I load 640 zeroes into the shift registers if the Crosspoint only have 256 switches? I can suppose you´re initializating

8 AD75019 connected in cascade, then my question is why only 80 bits per IC? Please comment.

Mauricio, my apologies. Ignore my post. The code is for a AD8113 chip, which is a 16X16 Video switcher. [Having just said that I've looked at the AD75019 data sheet and noticed the

256 bits of data are serially loaded and latched the same way as the AD8113]. regards john

Hi Andrew.

Square wave is 0 - 5V (5Vpp)

Vdd = +12V Vss = -12V Vcc = +5V

Pull down resistors 100K from each input to ground Yes, something´s wrong here.

Regards