Frequency counter? - E1 input rate?
Posted: Thu Jan 27, 2022 5:13 am
I would like to implement a frequency counter in the Red Pitaya, similar to one I implemented in a CPLD. That is a 20-bit counter with a digital clock up to 200 MHz; at 1 millisecond intervals the counter is copied to a 20-bit latch which is then read out by the host (a Teensy 4.0, which is an Arduino on steroids). It is important that there be no dead-time. Care must be taken because the counter and latch are different clock domains; fortunately the input clock is always a square wave (of slowly varying frequency).
On the Red Pitaya that could be done with two DSP slices and a handful of logic slices, or by a bigger handful of logic slices. Handling up to 200 MHz input is required; up to 400 MHz is highly desirable.
The challenge is the digital input. Ideally the E1 connector would accept an LVDS input up to 400 MHz (or at least up to 200 MHz). But from other posts it seems that the E1 inputs cannot be programmed to LVDS.
How fast can the E1 digital inputs be driven reliably by square waves? Can they do 200 MHz? 400 MHz? higher?
On the Red Pitaya that could be done with two DSP slices and a handful of logic slices, or by a bigger handful of logic slices. Handling up to 200 MHz input is required; up to 400 MHz is highly desirable.
The challenge is the digital input. Ideally the E1 connector would accept an LVDS input up to 400 MHz (or at least up to 200 MHz). But from other posts it seems that the E1 inputs cannot be programmed to LVDS.
How fast can the E1 digital inputs be driven reliably by square waves? Can they do 200 MHz? 400 MHz? higher?