I'm designing a test/loopback board for a laser controller. I went to engineering school for five years for this?
Anyway, I need to verify the SPI interface on the DUT; it comes out on a ribbon cable for our customer to use. I was thinking that I could put the dumbest, easiest to program SPI part in the world on my test board, and let the uP in the DUT pound on it to verify the link. So, what's the dumbest SPI chip on the planet?
--
John Larkin, President
Highland Technology, Inc
jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
4 wires? 3 wires? data on rising/falling edge of clock? minimum time from enable to clock? minimum time from last clock to ! enable? turn around from input to output on data? number of bits per read/write? to mention some
figure out what it needs to talk to and simulate that with what ever fpga/cpld board you have around
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:
A 74HC595 shift register and 8 LEDs with resistors.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
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.
--
John Larkin, President
Highland Technology, Inc
jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
How about a 25AA010AT 128x8 SPI EEPROM? Write and verify. SOT-23-6. Sells for 30 cents or so.
Best regards, Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
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.
--
John Larkin, President
Highland Technology, Inc
jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
The shift register does have input and output available, so I could test MISO/MOSI/CLOCK. But not CS, except by eyeballing LEDs.
--
John Larkin, President
Highland Technology, Inc
jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
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.
--
John Larkin, President
Highland Technology, Inc
jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
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.
--
John Larkin, President
Highland Technology, Inc
jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
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.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.