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cntr/README update: name clarification and bugs list.

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- cntr/README: change the name from "Arbitrary-precision counter" to
  "Arbitrary-precision frequency counter"
- cntr/README: added list of known hardware issues
This commit is contained in:
Werner Almesberger 2010-11-03 10:30:34 -03:00
parent 188bdb892b
commit c91658e1ed
1 changed files with 19 additions and 7 deletions
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cntr/README
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@ -1,14 +1,14 @@
Arbitrary-precision counter
===========================
Arbitrary-precision frequency counter
=====================================
Theory of operation
-------------------
The arbitrary-precision counter counts clock cycles of a frequency
source that is assumed to be free from drift. It compares the count
with the host's system clock. If the system clock is synchronized with
an accurate NTP reference, measurements with arbitrarily high accuracy
can be obtained.
The arbitrary-precision frequency counter counts clock cycles of a
frequency source that is assumed to be free from drift. It compares the
count with the host's system clock. If the system clock is synchronized
with an accurate NTP reference, measurements with arbitrarily high
accuracy can be obtained.
In practice, this is limited by the the frequency source's drift and
the time one is willing to wait. If NTP maintains the system time
@ -64,3 +64,15 @@ board can be queried with "cntr -i".
To update the firmware, run
cntr -r && sleep 1 && dfu-util -d 0x20b7:0xcb72 -D cntr.bin
Known issues (hardware)
-----------------------
- the MMCX connector is hard to solder because of its large thermal
capacitance and surface
- the lateral pads of the MMCX connector could be wider
- manufacturing tolerances can push the USB connector a bit inside
the board, making its signal pins overshoot the pads
- the ground fill under the LED causes a secondary cathode contact
(which is harmless on this case)