Actually GCC supporting Cortex. So, I am using Raisonance IDE plus GCC
Toolchain as a development environment. My current project functional
diagram is following:
+--- STM32 -- (Pulse Counter, TTL Generator, DDS
driver, GPSDO monitor)
GPSDO--LTC6957-3--| | |
| +--- AD9852 -- VFO -> |
| v
+------------------------------------------- TADD3 -- (1PPS, TTL) -->
As I'll finish it more or less, I'd like to compare the 1PPS which comes
directly from GPSDO with 1PPS which I could create on MCU (and probably
on DDS).
As I mention before, each STM MCU comes with very useful Peripheral
Library. That Library has tonnes of different examples.
Regards,
V.P.
On 2014-04-21 16:29, paul swed wrote:
Good afternoon very interested in the work you are doing with the STM
board.
As I mentioned far earlier in this thread I am attempting to use it to
correct the BPSK WWVB signal here. Initial thoughts were using FORTH
to program the STM board.
Very curious what you are using as examples.
My experience in FORTH is from many years ago and have done very
poorly at C. But this may be the case to have something of interest to
actually do. In either language.
Regards
Paul
WB8TSL
On Mon, Apr 14, 2014 at 12:27 PM, d0ct0r <[email protected]> wrote:
I was experimenting with the same setup for STM32 MCU. This
microprocessor has accept the sine wave from external OCXO or GPSDO.
No problem with this. The only thing: I was need to start MCU from
slow "watch" crystal first. And then switch it to work to external
one. In another case I got incorrect timing settings for MCU. Later,
I decide to implement LTC6957-3 chip to "share" REFCLOCK source,
since that chip has two equal CMOS-level outputs.
Unfortunately I have no tool to measure the phase noise and jitters
on each setup.
It turns out all of this is built into the AVR chip. There is a
counter
and logic to copy the current counter value to a register on a
PPS pulse
raising edge. The counter keeps running and every second its
value is
trapped.
I can connect the OCXO and the PPS directly to the AVR pin. The
AVR has
hardware (a fast comparator) to "square" a low amplitude sine
wave and trap
the counter on a zero crossing. So it looks like I can get rid
of ALL of
the external chips. The built in DAC is working well also but
it needs
some external resisters and caps.
No need for '74 FFs or '373' or counter chips. I do get
precision timing
with no time critical software, no 74xxx chips.
--
WBW,
V.P.
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WBW,
V.P.
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