[time-nuts] Frequency Counter Choice

[David]

Several USB--GPIB designs may be found on the web, for example, 

https://github.com/fenrir-naru/gpib-usbcdc/ 

I chose this one because it uses the bus driver chips, rather than
driving the bus directly with the microporcessor. 

It uses a  
http://www.silabs.com/products/mcu/8-bit/c8051f38x/Pages/c8051f38x.aspx 
microprocessor, and  

SN74ALS160, and SN74ALS162 bus driver chips.  It includes source code
and a (quite small) PC design, in Eagle. 

I've built this, with PC design modified to use a 32LQFP package.   

It works, at least for the simple use cases I've tried. 

David 

On 2020-11-08 15:51, Ben Bradley wrote:

> On Fri, Oct 23, 2020 at 9:14 AM jimlux <jimlux at earthlink.net> wrote: 
> 
>> ...
>> to be set - for instance, Arduinos work that way:
>> 
>> digitalWrite(pin#, HIGH)
>> 
>> I think GPIB would still work if you had to do 8 digitalWrite() calls,
>> then a final digitalWrite() call to assert DAV.
>> 
>> I suspect that for a number of Arduino type processors, there is a way
>> to write or read all 8 at once, assuming you were clever enough to pick
>> the right pins to use.
> 
> It's easy once you figure out which I/O ports you're using. I traced
> the AVR pinout and Arduino Mega 2560 schematic to translate between
> AVR ports and Arduino I/O pin numbers and to find the port I wanted to
> use. Googling found the port names that you can directly read from and
> write to in Arduino C/C++ code, as opposed to using the digitalwrite
> function for each bit. Here I used DDRC and PORTC:
> http://blog.freesideatlanta.org/2017/02/a-capacitive-touch-janko-keyboard-what.html
> 
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