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+.. _errata:
+
+========
+ Errata
+========
+
+This page is a collection of known issues and warnings for each
+revision of the Maple board. The failure modes aren't design errors,
+but are easy ways to break or damage your board permanently. For a
+list of differences between the Maple and Arduinos, see the
+:ref:`compatibility reference <compatibility>`.
+
+The errata are grouped by Maple version ("Rev").  Rev 5 is currently
+on sale.  If you are unsure which version you own, the :ref:`Maple
+hardware page <maple-hardware-identify-rev>` has pictures and
+descriptions of each version.
+
+.. contents:: Contents
+   :local:
+
+Maple Rev 5
+-----------
+
+Known issues:
+
+* **Pin 3 AIN missing**: Pin 3 is capable of analog input, but the
+    corresponding "AIN" is missing from its silkscreen.
+
+* **GPIO 39-43 not configured**: this is really more of a software
+  "TODO" item.  Some of the JTAG header pins are numbered 39-43. These
+  STM32 pins are indeed fully functional :ref:`GPIO <gpio>` when the a
+  :ref:`JTAG <jtag>` device is not connected, but we have not enabled
+  them in software and thus they can not be accessed with the regular
+  :ref:`lang-pinmode` or :ref:`lang-digitalwrite` functions.
+
+Potential failure modes:
+
+* **TTL voltage on non-tolerant pins**: not all header pins are 5V
+  compatible; connecting certain serial devices in the wrong way could
+  over voltage the pins.  The :ref:`Pin-Mapping Mega Table
+  <pin-mapping-mega-table>` details which pins are 5V-tolerant.
+
+Maple Rev 3
+-----------
+
+Known issues:
+
+* **Bad/Sticky Buttons**: a number of Rev 3 boards sold in May-June 2010
+  have questionable RESET and BUT buttons.
+
+  What seems to have happened is that the flux remover we used to
+  clean the boards before shipping eroded the plastic internals, which
+  resulted in intermittent functionality. All buttons on all shipped
+  boards did function in testing, but some may have been unreliable in
+  regular use.
+
+  If you have this problem, we will be happy to ship you new buttons
+  if you think you can re-solder them yourself, or you can ship us
+  your board and we will swap out that part.
+
+  For reference, the button part number is KMR211GLFS and the flux
+  remover we used is "Precision Electronics Cleaner" from RadioShack,
+  which is "Safe on most plastics" and contains Dipropylene glycol
+  monomethyl ether, hydrotreated heavy naphtha, dipropylene glycol
+  methyl ether acetate (really?), and carbon dioxide.
+
+* **Resistors on pins 0 and 1**: these header pins, which are RX/TX on
+  USART2 (:ref:`Serial2 <lang-serial>`), have resistors in-line
+  between the STM32 and the headers. These resistors increase the
+  impedance of the lines for ADC reads and affect the open drain GPIO
+  functionality of the pins.
+
+  These resistors were accidentally copied over from older Arduino USB
+  designs, where they appear to protect the USB-Serial converter from
+  TTL voltage on the headers.
+
+* **GPIO 39-43 not configured**: this is really more of a software
+  "TODO" item.  Some of the JTAG header pins are numbered 39-43. These
+  STM32 pins are indeed fully functional :ref:`GPIO <gpio>` when the a
+  :ref:`JTAG <jtag>` device is not connected, but we have not enabled
+  them in software and thus they can not be accessed with the regular
+  :ref:`lang-pinmode` or :ref:`lang-digitalwrite` functions.
+
+* **Silkscreen Errors**: the silkscreen on the bottom indicated PWM
+  functionality on pin 25 and listen the external header GND pin as
+  number 38 (actually 38 is connected to the BUT button). We manually
+  sharpied over both of these mistakes.
+
+* **PWM Marketing Mistake**: We originally sold the Maple advertising
+  22 channels of 16-bit hardware PWM; actually the Maple only has 15.
+
+Potential failure modes:
+
+* **TTL voltage on non-tolerant pins**: not all header pins are 5V
+  compatible; connecting certain serial devices in the wrong way could
+  over voltage the pins.  The :ref:`Pin-Mapping Mega Table
+  <pin-mapping-mega-table>` details which pins are 5V-tolerant.
+
+Maple Rev 1
+-----------
+
+Known issues:
+
+* **ADC noise**: generally very high, in particular when the USB port
+  is being used for communications (including keep-alive pings when
+  connected to a computer).
+
+  This issue was resolved in Rev 3 with a 4-layer design and a
+  geometrically isolated ADC V\ :sub:`ref` plane.
+
+* **Resistors on pins 0 and 1**: these header pins, which are RX/TX on
+  USART2 (:ref:`Serial2 <lang-serial>`), have resistors in-line
+  between the STM32 and the headers. These resistors increase the
+  impedance of the lines for ADC reads and affect the open drain GPIO
+  functionality of the pins.
+
+  These resistors were accidentally copied over from older Arduino USB
+  designs, where they appear to protect the USB-Serial converter from
+  TTL voltage on the headers.
+
+* **Silkscreen Differences**: the pin numbering scheme on Rev 1 is
+  different from Rev 3, and thus Rev 3 software is difficult to use
+  with Rev 1 boards. Notably, the analog input bank is labeled A0-A4
+  on Rev 1 but 15-20 on Rev 3, and the extra header bank does not have
+  a pinout table on the bottom.
+
+* **No BUT Button**: the BUT button, useful for serial bootloading,
+  was only added in Rev 3. As a workaround, you can directly short the
+  appropriate MCU pin to Vcc; see `this forum posting
+  <http://forums.leaflabs.com/topic.php?id=32#post-126>`_.
+
+* **PWM Marketing Mistake**: We originally sold the Maple advertising
+  22 channels of 16-bit hardware PWM; actually the Maple only has 15.
+
+Potential failure modes:
+
+* **TTL voltage on non-tolerant pins**: not all header pins are 5v
+  compatible; connecting certain serial devices in the wrong way could
+  over voltage the pins. The :ref:`Pin-Mapping Mega Table
+  <pin-mapping-mega-table>` details which pins are 5V-tolerant.