add bugs.txt to keep track of PCB issues over the revisions, and their fixes

kicad/bugs.txt

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+
+Known bugs
+
+Revision Current (no date yet)
+------------------------------
+
+
+Revision 2022-06-07
+-------------------
+- The LEDs for all bidirectional signals are activated only by pullups, which may lead
+  to low brightness and a signal voltage level that is below the desired 5V.
+  Workaround: Solder the LEDs in reverse and connect them to 5V instead of GND, as the
+  signal LOW state can sink more current. Will be fixed upon redesign/cleanup.
+
+- ESP32 (azdelivery) has a wrong symbol where the "CMD" pin is labelled as GND, which
+  resulted in a short to GND on this pin.
+  Workaround: Remove the contacts from the pinheader that connects the PCB to the ESP.
+  Will be fixed upon redesign/cleanup.
+
+- ESP32 GPIO12 is not supposed to be pulled up HIGH during boot (the pin doubles as a
+  bootstrapping pin, and will result in a boot loop if set to HIGH)
+  Workaround: Cut trace at the GPIO12 pin, connect the signal to GPIO13
+  Will be fixed upon redesign/cleanup.
+
+- The ESP isn't programmable when inserted into the socket on the PCB. More and more
+  bootstrapping issues. In the end, the following remapping was necessary in total:
+  Signal          Old      New
+  ESP_D0          GPIO12   GPIO13 ok
+  ESP_D5          GPIO5    GPIO18 ok
+  ESP_STROBE      GPIO15   GPIO19 ok
+  ESP_AUTOFD      GPIO2    -
+  ESP_PAPER_EMPTY GPIO19   -