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, slightly outside spec before
  • Move GPS Reset line to more appropriate MCU pin, and relocated pull-down for it
  • Correct silk on C15 (was marked incorrectly as C31)
  • RJ45 jack LED resistors replaced by resistor array
  • Current-limit resistors between MCP2200 and MCU replaced with array
  • Resistors for USB VBUS sense connected to MCP2200 reset line replaced with array
  • Corrected several component values which had been left unaltered from copies
  • Make space for 16x16x4mm fan in one of the endplates, hard powered up (no PWM control)
  • Reposition LDO regulator to allow it to have a heatsink glued to it
  • ENC424J600 CS line now driven by MCU, with external pull-down
  • Add pull-up on DS3234 CS line so it’s deselected by default

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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