05 Dec 06
 host software:
  (utils): lpfilter corrected; stat added
  (conloq): garmin_nmea.c corrected
  (postproc): quick and dirty postprocessing added
29 Nov 06
 new board ordered. gerbers should be reoutput with new version
 of PCB: it doesn't overcomplicate files with multiple layers which
 are imported to different layers by some CADs (misinterpreting 
 the format specification)
24 Sept 06
 host software (utils): fdif added; drift corrected
22 Sept 06
 host software (utils): added an utility to estimate sensors drifts;
 lpfilter now can be ordered to change output precision.

28 Aug 06
 hardware: R15, R16, R32, R33, R34 deleted from main board.

05 Jul 06
 hardware: R31 changed to 1k. Q2 replaced with IRF7507. extra 3.3V regulator
 added to increase the higher working temperature limit.

04 Jul 06
 host software: brief form of decoding added (exp-brief.c); this should
  improve stability of conloq. elk timeouts decreased

 hardware: ADXL210AE appear to be obsolete. the nearest replacement is ADXL213;
  the dynamics range is not so wide, though. ST make next-generation
  accelerometers, but they are not easily available now, and they lack PWM
  channels.
  
22 Jun 06
 hardware: sym/IRF7507.sym added. this probably will replace IRF7317:
 the latter has too high gate charges. LPC213x can't drive it purely.

 C35 would better be 2.0uF 1210 ceramic.

 The temperature drifts are being researched thoroughly.

07 Jun 06
hardware: added OP495GS to compensate HMC10xx offset resistances drift vs temperature.
 a branch of main board introduced where the magnetoresistors moved away from
 other parts which appeared to be magnetic.

 The second exemplar of the main board is being soldered. INA126U will be
 mounted in place of INA118. they are some 6 dB cheaper, but should fit.

27 May 06
target software: (multa) 
 ADC readings for gyros and temperatures adjusted for MCU
 power supply changes; namely, adc_i(out)=(adc_i(in)*k)>>21), where
 k=(a0*a0-(D-a0)*(a0+17)+(D-a0)*(D-a0)*5+42*1024, D is lowpass-filtered readings 
 of 2.048V from the DAC, a0 is 641 - typical value of D. 
 these factors possibly will need correction for every single board.

 adc_i(in)*k<=1<<32 and k/(double)(1<<21) is approximately a0/D for small (D-a0).
 -0.0005<a0/D-k/2^21<0.0005 when -70<(D-a0)<80
 So, for usual temperatures the corrected ADC readings remain the same, 
 whereas for the higher, when the supply voltage decreases, ADC readings 
 are corrected with error less than ADC unit.

 Initial readings can be reconstructed at the host side with uncertainty of 
 1 unit.

 Looking for excluding spurs in accelerometers measurements.

host software: (exp.c) 
 ADC temperature and 2.048V readings added to the end of 'adc:' string.

18 May 06
 target software: corrected directions of magnetic axes
15 May 06
 host software: elk now can load LPC2138 non-interactively
 conloq shows low-pass filtered values of measurements
 elig added
17 Apr 06
 burnt input A. adding possibility to get PPS at SCL.
15 Apr 06
 mag_response: ADC differences added to output
 magex: weak checksum added
 host software: simple low-pass filtering program added

09 Apr 06
a week ago stribog had a field test. the next corrections followed:
 target software: magnetic sampling frequency adjusted to 16*50 Hz;
  magex: raw 800 Hz output (without chechsums) added
  uart0.c: more reasonable input function
  multa.c: measurements output rate changed to 200 Hz
 host software: a parser for magex output written
  conloq: GPS parser (initially) added
 main board: x and y axes drawn.

31 Mar 06
 target software: UART0 functions written; accelerometer channels
  sequence changed to conform with the magnetic sensors. 
 host software: limited Win32 support added

22 Mar 06
 all on-board sensors do work. magnetic sensors bandwidth should be
 defined more precisely and increased.
 mag_response program added: it is to measure DAC response to magnetic
 sensors output. the measured values define kx, ky and kz in mag.c
C35 is tantalum again.

18 Mar 06
fixed a bug in the hardware part: pins 2 and 4 of Q2 must be swapped
 resistance R33 decreased to 30 Ohm.
 initially added a software module for magnetic sensors

04 Mar 06 
added pullup resistor to RESET
R17..R20 changed to 2.2k, R21..R24 --- to 3.3k

24 Feb 06
 LEDs added
 Tantalum capacitor C35 replaced with ceramic 0805
