[time-nuts] [Solved] Looking for multiple PPS timestamp logging

Kevin Rosenberg kevin at rosenberg.net
Wed Oct 5 16:29:09 EDT 2011


On Oct 4, 2011, at 10:16 AM, Tijd Dingen wrote:
> You mentioned wanting to use the parallel port under linux for pps purposes, right?

Hi Fred, I consider it, but tvb's picPET's will work much better for the project.

> So if some parallel port programming is acceptable, then you can do the following:
> - get an adc with SPI bus (which means plenty of choice)
> - connect the 3 SPI wires to parallel port
> - bitbang spi (just google "bitbang spi" and you'll find example code. it's pretty simple to do yourself and a fairly forgiving protocol (timing wise))

I like SPI as well and have done a fair bit of AVR bit banging. Doing it though the parallel port is intriguing.

> Alternatively you could use a microcontroller with both spi and uart (microchip and atmel have plenty), and use that to serve as uart <--> spi bridge. Or for something like a 10 bit ADC you can use the internal adc of the MCU. 

I'm leaning toward an ATMega168 which has a USART and a TWI interface, 
so simplify programming and work at the byte rather than bit level.

> - get an ADS1258EVM board for about $50
> - bring your own supply voltage
> - bitbang spi on the parallel port
> - bitbang i2c on the parallel port (this is optional for this board, not strictly needed)

That's a nice board. I ended up ordering the PDK version which comes with a some
other features including a USB interface so can skip worrying about having a parallel
port on whatever system I'll be using the ADS1258EVM with. Creating a fpga interface
like you did is a fine idea, but I'll end up trading some dollars for time with the PDK
version.

Kevin






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