dumbest SPI chip

spi input or spi output ??

spi does not come without a peripheral or a cpu attached.

So you need an spi output .... right ?

The spi talks to ..... what ?

spi can be so many thing it is impossible to say.

figure out what it needs to talk to and simulate that with what ever fpga/cpld board you have around

-Lasse

I'd say, if you're familiar with them, that one of the PICs is about as easy as it gets. We use these for quick and dirty test interfaces around our labs:

What about an SPI relay driver?

Use the outputs to blink some LEDs, or something.

A 74HC595 shift register and 8 LEDs with resistors.

Cheers

Phil Hobbs

The board I'm trying to test has an ARM processor with an SPI port: MISO, MOSI, ChipSelect, SPIclock, all brought out on a ribbon cable. I need to test that port, so I need a target device.

How about a 25AA010AT 128x8 SPI EEPROM? Write and verify. SOT-23-6. Sells for 30 cents or so.

Best regards, Spehro Pefhany

Or NXP has some LED/Peripheral drivers that are SPI/I2C

Or maybe these are too Dumb.

Cheers

DOS and bit banging the parallel port.

The only disadvantage I see with the 74HC595 is that it doesn't have a MISO pin, so there's no way to verify that that component of the protocol is working correctly.

I need something I can write to and read back from, to test all four SPI port lines.

I could loop MOSI to MISO; we verified that the ARM will talk to itself that way, but that doesn't test chip select or clock integrity, and MISO could be shorted to MOSI on the DUT board, and we'd miss that. Policy is that a production test should catch all reasonably possible opens/shorts/bad parts/assembly errors.

Maybe I'll just use an SPI eeprom, and write a 16-bit test pattern then read it back. That would test the entire port, but that is a mild nuisance to program. But then, I don't have to write the code!

The HC595 works if I shift 16 bits in and out and manually read the LEDs, but that's not as automated as it might be.

The shift register does have input and output available, so I could test MISO/MOSI/CLOCK. But not CS, except by eyeballing LEDs.

Oh right, I forgot about the daisy chaining output.

No, it's the other way: the DUT has an ARM with a master SPI port, and I need a target devive to prove that the SPI port works. I want to put that on my test board.

Yeah, I might just use an EEPROM. We have SO8's in stock, AT93C86A. It's a little messy to program, but not too bad.

Aren't they Microwire rather than SPI?

Best regards, Spehro Pefhany

You can daisy chain them--put SDO to MISO.

Cheers

Phil Hobbs

even easier then, just configure the pins as GPIO in the test program and test the connections that way

-Lasse

Do you have complete control of the SPI interface? How about a dual D-FF? Connect D1 to MOSI, SCK to Clk1, Q1 to D2, SS to Clk2, and Q2 to MISO; a 1-bit SPI port.