[time-nuts] What's available in the way of DSP for new WWVB?

[Graham / KE9H]

On Tue, Oct 13, 2020 at 12:19 PM paul swed <paulswedb at gmail.com> wrote:

> Graham take a look earlier in the thread there are details about the
> teensy. There is actually a lot of hardware out there today for little
> money. Thats what makes the SDR DSP approach interesting and for me at
> least the next thing to take a run at.
> Regards
> Paul
> WB8TSL
>
>
> Hi Paul:

I have looked at the Teensy 4.0 for use as a WWVB SDR receiver.

The problems I have are:

1.) PJRC (the designer/manufacturer) has gone out of their way to block
access to the standard ARM SWD programming interface, and you must go
through the unique USB loader executable and programming interface if you
want to program the board. It is awkward to use a normal development
environment such as NXP's MCUXpresso with a standard programming interface.
It is really intended for use with the provided Arduino programming
environment.

2.) If you use the provided Arduino IDE/environment, then the provided DSP
functions are restricted to the 16 bit versions. I prefer the ARM 32 bit
versions to go with my 19 to 24 bit data converter.

3.) I have found that the iMX RT1062 processor will only run at the
advertised 600 MHz speed, if it is exclusively executing from onboard
"tightly coupled RAM". If your program is large enough to require using the
OCRAM, then it slows down to 1/4 speed.  If you need even more memory
space, and you try to use the provided external QSPI Flash, then it slows
down to about 1/32 speed. What it effectively does is run at some blend of
those speeds as it fetches cache and variously accesses the different
memories.  Memory planning is critical for maximum performance.

--- Graham

==