USB2LPT – Cloning instructions for Release 1.6

It's not hard to populate this PCB.

 
(Sufficiently) populated PCB

• off:
  • No power supply (cable broken or similar)
  • USB2LPT not recognized by computer
  • USB Standby mode - e.g. at notebook's suspend mode
  • USB2LPT in bootloader mode
• on:
  • USB2LPT active, output drivers enabled, inputs with pull-up resistors
• flashing:
  • fast: USB BULK or INTERRUPT transfers (redirected IN and OUT instructions; normal operation)
  • slow: USB CONTROL transfers (mostly initiated by Windows)

• Schematic and PCB, Source
• For Windows driver and AVR firmware, see page above, and how-to-use instructions.
  Here you can browse the firmware source in your web browser.

• Drill holes into SubD shell for LED
• Label the shell
• Bend pins of USB receptacle straight – see picture
• Trim pins of LED and electrolytic capacitor to about 1 cm length
• Download and install either PonyProg or WinAVR
• PonyProg: Setup interface as shown here, check by connecting the programming adapter (this checks for connection between Pin 2 and Pin 12), invoke Setup→Calibration

New: The do-it-yourself process for the similar 1.7 version is available at YouTube! (Three parts, running time ca. 30 minutes, German comments, English subtitling)

1. Solder paste applying, SMD population
2. SMD population (cont.), Reflow process, SubD receptacle
3. USB receptacle, LED, Housing shell, Final check

• put SMD cream, 4 SMD components, make a reflow process – or solder by hand
• Check for short circuit between 5 volts and ground
• press and solder SubD receptacle keeping ½ mm gap between PCB and SubD shroud
• Align and solder USB receptacle (see helper tool), solder the pins with lowest possible iron temperature
• Populate electrolytic capacitor as flat as possible
• Align and solder the LED using the shell, watch for right polarity
• Check for short circuit between 5 volts and ground again
• Check “operation” by connecting the USB cable, must show as “inoperational USB device”, this is the power supply for programming the bootloader
• Connect programming adapter to an old-style parallel port and program the bootloader, either
  • PonyProg: load main.hex, write, set fuses exactly as shown here
    Do not twiddle with the fuses without knowledge! You may make the ATmega unaccessible to PonyProg and all other low-voltage serial programmers!
    or
  • WinAVR: invoke make prog (directory src/firmware/USB2LPT6/bootloadHID)
  If your programming software doesn't recognize the right controller, check:
  • Programming adapter soldered correctly?
  • Programming adapter used in correct direction?
  • Solder jumper SJ2 (still) connected?
  • Pins of SubD25 socket soldered correctly?
  • Microcontroller soldered in correct alignment and angle? (If wrong, remove with a hot-air gun. If 180° wrong, use new ATmega8.)
  • Mikrocontroller soldered without shorts?
• Cycle power to USB2LPT, let install driver usb2lpt.inf. The Bootloader ( HIDboot) will not occur because the .hex file above contains both bootloader and the real USB2LPT firmware.
  If there is no USB2LPT, then check:
  • Solder joints on USB socket correctly?
  • USB socket not melted? (Contact springs still visible?)
  • SMD solder joints correctly without shorts?
  Check with another computer and/or with front-side or back-side USB connectors on PC, or using a USB hub. If USB2LPT seems to work unreliable, populating the crystal and downgrading to USB2LPT 1.5 firmware may help. The reason is an unstable 5V supply, that jitters the internal RC oscillator of the 1.6 firmware solution.
• Remove programming adapter
• Scratch jumper SJ2 (the only solder jumper on silk-screen-less lower PCB side)
• Connect LPT checker or similar device, run Kurzschlusstest.exe, make corrections if necessary
  Alternatively, download fw-utils.en.zip first for English message utilities (it's not supported by me).
• Close shell, make a final check

• The crystal and the both 22 pF capacitors are not to populate
• Population with ATmegaX8 is currently not recommended.
  If you want ATmega48 population, R₁ should be 4.7 kΩ, and the older firmware USB2LPT5 (and crystal) must be used. A bootloader cannot be used (this chip has no bootloader support)
• If D₂ (BAV199) is used, R₁ must be 1.5 kΩ
• The 5 V USB interface with 220 Ω series resistors is incompatible to some notebooks. In such a case, the device will not be recognized correctly, and you see „Unknown device“. No driver installation will help here, and any force may damage your Windows installation.
  Possible solutions:
  • Use a USB hub in between, or an active extension cable (which is essentially a one-port hub).
  • Change components to 3.3 V design, i.e. populate the BAV199 as stated above. Of course, this will result in 3.3 V I/O voltages, and the inputs are then not truly 5.0 V compliant.
  • Populate flying 3.9 V zener diodes to USB D+ and D- wires.

• SJ1 can assign power to pin 25 of SubD receptacle:
  • open: Pin 25 unbeschaltet
  • right connected: Pin 25 to ground (default)
  • left connected: Pin 25 to 5 volts
  If power is needed, populating a self-resetting fuse is highly recommended.

• SJ2, connected at PCB fabrication, scratched at device manufacturing: activates the RESET pin of ATmega for programming the microcontroller.

• SJ3, connected by default, scratch when you want 3.3 volts operation of ATmega8 (e.g. for safer JTAG connection), populate a BAV199 and change R₁. Moreover, scatch it to measure device's current consumption and re-solder.