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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 Theory of operation
------------------- -------------------
The arbitrary-precision counter counts clock cycles of a frequency The arbitrary-precision frequency counter counts clock cycles of a
source that is assumed to be free from drift. It compares the count frequency source that is assumed to be free from drift. It compares the
with the host's system clock. If the system clock is synchronized with count with the host's system clock. If the system clock is synchronized
an accurate NTP reference, measurements with arbitrarily high accuracy with an accurate NTP reference, measurements with arbitrarily high
can be obtained. accuracy can be obtained.
In practice, this is limited by the the frequency source's drift and 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 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 To update the firmware, run
cntr -r && sleep 1 && dfu-util -d 0x20b7:0xcb72 -D cntr.bin 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)