I have an AT90USB162, have it set up like this: enter image description here

I'm trying to program the chip using Atmel FLIP, but I can't because it's not detected. What could be the problem and how can I fix it?

  • \$\begingroup\$ Please rephrase your post to ask a specific question. \$\endgroup\$
    – Daniel
    Commented Aug 9, 2018 at 16:12
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    \$\begingroup\$ Is the _RESET pin really floating in your design? \$\endgroup\$
    – user39382
    Commented Aug 9, 2018 at 17:36
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    \$\begingroup\$ Isn't it that the default crystal is 8 MHz, not 16? \$\endgroup\$ Commented Aug 9, 2018 at 17:59
  • \$\begingroup\$ Reset pin has an internal pullup, confirmed with meter and the documentation. @AliChen I have no idea what you mean by "default" \$\endgroup\$ Commented Aug 10, 2018 at 2:47
  • \$\begingroup\$ I mean that OLIMEX development kit for AT90USB162 uses 8 MHz crystal. Before developing something for USB, one should acquire at least basic ideas how it works, at least how it starts. And USB starts with device pulling up D+ high. Does your device do it? Does the host respond with USB_RESET? Then, USB device should respond with certain frequency of bits in packets, 83.33 nS per bit. Does it? Does your crystal (and default fusing/lockbit settings/whatever) provide the 83.3 ns bit pattern? \$\endgroup\$ Commented Aug 10, 2018 at 3:02

1 Answer 1


You need to pull HWB low while coming out of (power-on) reset, or else the bootloader will simply idle when it finds no valid program in flash.

  • \$\begingroup\$ Yep, +1, the reference design shows 10k-100nF RC delay on pin 13, sparkfun.com/datasheets/AVR/AVR-USB-162-sch.gif \$\endgroup\$ Commented Aug 10, 2018 at 3:10
  • \$\begingroup\$ I already tried pulling it low, didn't do anything. \$\endgroup\$ Commented Aug 17, 2018 at 1:46
  • \$\begingroup\$ @MátéVarga You need to pull #RESET low, then pull #HWB low, then release #RESET while HWB is still low. It is sampled once on the rising edge of #RESET. Because you rely on Power-on-Reset (POR), you need to hold #HWB low while plugging in the USB cable. \$\endgroup\$
    – FRob
    Commented Aug 17, 2018 at 8:15

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