NTP Server Project History

A placeholder for release notes, while I work out what the complete history is.

Version 1.5 – TBD

  • Fixup Ethernet TX/RX magnetics and filtering (centre tap on RX side should be grounded not pulled up, reposition 6.8nF caps to be close to jack rather than IC, centre tap on TX side powering should have filter cap inside the current limit resistor not outside)
  • Shifted around the bus connection between ENC424J600 and MCU so it is easier to avoid PSU area
  • Relocated board status LEDs to suit new ethernet bus connection
  • Correct silk on C15 (was marked incorrectly as C31)
  • Corrected several component values which had been left unaltered from copies
  • Replace LDO linear regulator with switch mode DC-DC regulator
  • Replace reverse polarity protection diode with P-channel MOSFET
  • Correct missing USB shielding requirements for HS cables
  • Correct MCP2200 power connections for 3.3V
  • Remove “Recovery” jumper
  • Remove external flash chip – XBOOT bootloader provides in-firmware update methods which don’t require any external storage and will work over any method I like
  • Remove holes from board corners, they haven’t been useful
  • Add connection to SQW output from DS3234. Could be useful for easy comparison of DS3234 drift

Version 1.4 – 14 November 2011

  • Switch from MEGA to XMEGA MCU line, using 192D3 (64-pin 0.8mm TQFP). Will accept either D3 or A3 chips.
  • Single status LED broken down to three¬†separate LEDs, driven from PWM lines. Colours are intended to be Red, Yellow, Green.
  • Remove power LED.
  • Switch to 8-SOIC Wide package for recovery/update flash chip
  • Most passives reduced in size from 0805 to 0603, some repeated resistors replaced with 0603 networks. Many sections of passives (eg, Ethernet front end) tidied up as a result.
  • Replace 20ppm watch crystal with DS3234 TCXO, providing 2ppm accuracy without calibration.
  • Revert GPS chip to Trimble¬†Copernicus
  • Add fuse to GPS antenna power, to prevent shorts killing GPS chip or power supply. No detection of shorts.
  • Remove externally-reachable switch, unused in several revisions and bootloader access will be handled by other means.
  • Replace JTAG interface with PDI – JTAG is not supported on XMEGA D-family chips.
  • GPS reset controlled by MCU, more reliable sync up with protocol from GPS.
  • Replace PTH reverse polarity protection diode with SMD part.
  • Reset pull-up is present but shouldn’t be populated, should not be required by XMEGA chips.
  • Increase board width to match case more closely, to hold in place better

Version 1.3 – 2010

  • Add back in factory-reset switch. Again.
  • Add AT25DF external flash chip
  • Add “Recovery” jumper to restore backup system image from external flash.
  • Replace FT232RL with MCP2200 USB serial chip
  • Remove ISP/SPI, in favour of JTAG
  • Remove CS line being sourced from MCU, pulled up by resistor instead
  • Add power LED
  • Relocate bi-colour LED
  • Add ESD protection to USB port
  • Relocate load limiting resistors for RJ45 jack LEDs to improve routing

Version 1.2 – 2010

  • Purely 3.3V design, removal of all 5V sources and parts
  • Remove level shifting between GPS, Ethernet, and MCU
  • Switched to larger flash MCU, from 644P to 1284P (same pinouts)
  • Reorientate MCU to provide better access to all the pins needed to new Ethernet chip
  • Replace 4.194304MHz crystal with 32.768kHz one
  • Replace ENC28J60 with ENC424J600, bigger and betterer.
  • Remove factory-set MAC address chip, ENC424J600 has unique MAC built in.
  • All crystals are now SMD, except 32.768kHz.
  • Switch to Venus634FLP GPS chip
  • Remove externally accessible factory reset switch
  • Improve power handling, add missing decoupling caps from many VCC/GND pairs
  • (Atempt) Re-layout Ethernet front-end to match ENCx24J600 datasheets
  • Adjust board dimensions to take into account case ends.

Version 1.1 – 2009

  • First design made for target case (50x80mm board)
  • Mostly SMD components to replace PTH
  • Replaced discrete LEDs with single bi-colour LED
  • JTAG removed
  • MAX232 replaced with FT232RL for USB serial support
  • Reset button removed
  • Added 4.194304MHz cystal, testing alternative clocks to usual 32.768kHz.

Version 1.0 – 2009

  • Never built.

Version 0.1 – 2009

  • Replace all SMD parts with PTH parts, easier to solder.
  • Correct cap on ENC28J60 to be non-polarised
  • Correct caps on noise filtering section of Ethernet input
  • TX to GPS is properly level shifted.
  • Fix missing ground lines to RX level shifter to GPS and ENC28J60
  • Add JTAG port
  • Add power switch
  • Placement of crystal load caps improved
  • Add additional switch, targetted for “factory reset”
  • Remove “PORT A” header
  • Remove DTR reset control
  • Add external factory-set MAC address chip

Version 0.0 – 2009

  • First complete design and PCB produced.
  • Added GPS over prior breadboard designs.

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