Populated load capacitors of the crystal. Started organizing issues in ECNs.

- atrf/ecn/INDEX: ECN index
- atrf/ecn/ecn0001.txt: Adjust balun component values (pending)
- atrf/ecn/ecn0002.txt: Add load capacitors to 16 MHz crystal (C14, C15)
- atrf.sch, atrf/wpan-atrf.brd: changed load capacitors from NC to 12 pF
- atrf/ecn/ecn0003.txt: Replace balun and filter with integrated balun
  (pending)
- TODO: one more CNTR-related task

TODO

@@ -132,3 +132,6 @@ Things not done yet
   old.max < curr.min or old.min > curr.max, we have a problem) and to further
   narrow the effective margin, thus achieving faster convergence. We would have
   to consider temperature drift of the frequency source in this case.
+
+- find out why frequency measurements always seem to start high and then slowly
+  drop

atrf/atrf.sch

@@ -1,4 +1,4 @@
-EESchema Schematic File Version 2  date Wed Aug 25 19:40:58 2010
+EESchema Schematic File Version 2  date Thu Aug 26 00:07:13 2010
 LIBS:power
 LIBS:device
 LIBS:conn
@@ -7,12 +7,13 @@ LIBS:c8051f326
 LIBS:mini_usb_b
 LIBS:xtal-4
 LIBS:antenna
+LIBS:wpan-atrf-cache
 EELAYER 24  0
 EELAYER END
 $Descr A4 11700 8267
 Sheet 3 3
 Title "IEEE 802.15.4 USB Transceiver (AT86RF230)"
-Date "20 aug 2010"
+Date "26 aug 2010"
 Rev "100820"
 Comp "Werner Almesberger"
 Comment1 ""
@@ -619,7 +620,7 @@ L C C15
 U 1 1 4C640A7B
 P 10100 2450
 F 0 "C15" H 10150 2550 50  0000 L CNN
-F 1 "NC" H 10150 2350 50  0000 L CNN
+F 1 "12pF" H 10150 2350 50  0000 L CNN
 F 2 "0402" H 10100 2450 60  0001 C CNN
 	1    10100 2450
 	0    -1   1    0   
@@ -639,7 +640,7 @@ L C C14
 U 1 1 4C640A73
 P 10100 1150
 F 0 "C14" H 10150 1250 50  0000 L CNN
-F 1 "NC" H 10150 1050 50  0000 L CNN
+F 1 "12pF" H 10150 1050 50  0000 L CNN
 F 2 "0402" H 10100 1150 60  0001 C CNN
 	1    10100 1150
 	0    -1   1    0   

atrf/ecn/INDEX

@@ -0,0 +1,5 @@
+Number	Status	Description
+------	-------	---------------------------------------------------------------
+0001	Edit	Adjust balun component values
+0002	Done	Add load capacitors to 16 MHz crystal
+0003	Edit	Replace balun and filter with integrated balun

atrf/ecn/ecn0001.txt

@@ -0,0 +1,15 @@
+Adjust balun component values
+
+Some of the components specified in the schematics were not at hand
+in my lab and were thus replaced with similar parts. Furthermore, the
+LED color was changed to ease visual identification:
+
+Component	Norminal	Board 1		Board 2
+---------------	---------------	---------------	-------------------
+LED (D1)	red		red		red-orange
+C6/C7		0.82 pF		0.7 pF		0.9 pF
+L2/L3		4.3 nH		4.7 nH		4.7 nH
+
+The resulting spectrum should be examined to determine which variant
+performs better. Note that the discrete balun circuit shall be
+replaced with an integrated balun later on.

atrf/ecn/ecn0002.txt

@@ -0,0 +1,42 @@
+Add load capacitors to 16 MHz crystal (C14, C15)
+
+The crystal has a specified load capacitance of 8 pF. The AT86RF230 has
+an internal capacitor array that can be trimmed in 16 steps from 0 pF to
+4.5 pF.
+
+The crystal has a nominal tolerance of 15 ppm at 25 C plus a temperature
+tolerance of 15 ppm. The following deviations from 1 MHz at CLKM were
+measured with the CNTR board, roughly at 20-25 C:
+
+Board		Error		Meas. accuracy	C14/C15		Trim
+		(f, ppm)	(ppm, nom.)	(pF)		(pF)
+---------------	---------------	---------------	------------	--------
+2, "orange"	+268		 99.6		NC		0
+		+266		 99.5		NC		0
+		+266		 40.0		NC		0
+		+148		 99.8		NC		3.0
+		+147		 99.7		NC		3.0
+		+147		 40.0		NC		3.0
+		+111		100.0		NC		4.5
+		+110		 99.8		NC		4.5
+		- 13		 99.9		15		0
+		- 14		100.0		15		0
+		+ 11		 99.9		12		0
+		+ 11		 99.6		12		0
+
+1, "red"	+263		 99.7		NC		0
+		+263		100.0		NC		0
+		+107		 99.3		NC		4.5
+		+108		100.0		NC		4.5
+		+ 24		 99.8		10		0
+		+ 24		100.0		10		0
+		-  9		 99.7		10		4.5
+		-  9		100.0		10		4.5
+
+(Multiple measurements to assess CNTR performance and drift. Note that
+CNTR measurements are repeatable within 1 ppm, so the nominal accuracy
+appears to be far too pessimistic.)
+
+These measurements suggest that, combined with parasitic capacitance,
+load capacitors of 12 pF make the crystal roughly half the trim range
+faster than 16 MHz.

atrf/ecn/ecn0003.txt

@@ -0,0 +1,3 @@
+Replace balun and filter with integrated balun
+
+(pick suitable balun)

atrf/wpan-atrf.brd

@@ -1,4 +1,4 @@
-PCBNEW-BOARD Version 1 date Wed Aug 25 19:41:49 2010
+PCBNEW-BOARD Version 1 date Thu Aug 26 00:07:51 2010
 
 # Created by Pcbnew(2010-08-11 BZR 2448)-unstable
 
@@ -20,7 +20,7 @@ $EndGENERAL
 $SHEETDESCR
 Sheet A4 11700 8267
 Title "IEEE 802.15.4 USB Transceiver (AT86RF230)"
-Date "25 aug 2010"
+Date "26 aug 2010"
 Rev "100820"
 Comp "Werner Almesberger"
 Comment1 ""
@@ -341,7 +341,7 @@ AR /4C609C08/4C640A7B
 Op 0 0 0
 At SMD 
 T0 0 -150 200 200 1800 40 N V 25 N"C15"
-T1 0 150 200 200 1800 40 N I 25 N"NC"
+T1 0 150 200 200 1800 40 N I 25 N"12pF"
 DS -305 168 -305 -168 50 21
 DS -305 -168 305 -168 50 21
 DS 305 -168 305 168 50 21
@@ -369,7 +369,7 @@ AR /4C609C08/4C640A73
 Op 0 0 0
 At SMD 
 T0 0 -150 200 200 0 40 N V 25 N"C14"
-T1 0 150 200 200 0 40 N I 25 N"NC"
+T1 0 150 200 200 0 40 N I 25 N"12pF"
 DS -305 168 -305 -168 50 21
 DS -305 -168 305 -168 50 21
 DS 305 -168 305 168 50 21
@@ -2760,7 +2760,7 @@ ZLayer 0
 ZAux 4 E
 ZClearance 80 T
 ZMinThickness 70
-ZOptions 1 16 S 100 80
+ZOptions 1 16 F 100 80
 ZCorner 48800 40500 0
 ZCorner 48800 34300 0
 ZCorner 40700 34300 0
@@ -3132,7 +3132,7 @@ ZLayer 0
 ZAux 6 E
 ZClearance 80 T
 ZMinThickness 70
-ZOptions 1 16 S 100 80
+ZOptions 1 16 F 100 80
 ZCorner 62100 41100 0
 ZCorner 62100 39100 0
 ZCorner 56100 39100 0
@@ -3272,7 +3272,7 @@ ZLayer 0
 ZAux 4 E
 ZClearance 80 T
 ZMinThickness 70
-ZOptions 1 16 S 100 80
+ZOptions 1 16 F 100 80
 ZCorner 53900 41100 0
 ZCorner 53900 38400 0
 ZCorner 52600 38400 0
@@ -3357,7 +3357,7 @@ ZLayer 15
 ZAux 7 E
 ZClearance 80 T
 ZMinThickness 70
-ZOptions 1 16 S 100 80
+ZOptions 1 16 F 100 80
 ZCorner 52500 41100 0
 ZCorner 52500 38400 0
 ZCorner 52000 38400 0
@@ -3631,7 +3631,7 @@ ZLayer 15
 ZAux 4 E
 ZClearance 80 T
 ZMinThickness 70
-ZOptions 1 16 S 100 80
+ZOptions 1 16 F 100 80
 ZCorner 53900 41100 0
 ZCorner 53900 38400 0
 ZCorner 52600 38400 0
@@ -3824,7 +3824,7 @@ ZLayer 0
 ZAux 7 E
 ZClearance 80 T
 ZMinThickness 70
-ZOptions 1 16 S 100 80
+ZOptions 1 16 F 100 80
 ZCorner 52500 41100 0
 ZCorner 52500 38400 0
 ZCorner 52000 38400 0
@@ -3897,7 +3897,7 @@ ZLayer 15
 ZAux 4 E
 ZClearance 80 T
 ZMinThickness 70
-ZOptions 1 16 S 100 80
+ZOptions 1 16 F 100 80
 ZCorner 56100 41100 0
 ZCorner 56100 36800 0
 ZCorner 54200 36800 0
@@ -4204,7 +4204,7 @@ ZLayer 0
 ZAux 11 E
 ZClearance 80 T
 ZMinThickness 70
-ZOptions 1 16 S 100 80
+ZOptions 1 16 F 100 80
 ZCorner 50600 39100 0
 ZCorner 50800 38900 0
 ZCorner 51200 38900 0