RTD Built in Libraries & Arduino Variations

docs/arduino-variations.rst

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+Arduino Variations
+====================
+
+Functions and Options Differences
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Extra modes (if patches applied)
+---------------------------------
+
+This section covers the differences between standard Arduino and XMC-for-Arduino
+
+GPIO
++++++
+
+Extra pinMode types added that most engineers want
+
+.. code-block:: 
+
+    INPUT_PULLDOWN
+    OUTPUT_OPENDRAIN
+
+
+Extra functions (than standard Arduino AVR)
+--------------------------------------------
+
+GPIO
++++++
+Does what the function names says but must have been configured as output
+
+.. code-block:: 
+
+    digitalToggle( pin )
+
+Arduino Function Differences
+-------------------------------
+
+Input Mode Pins
+++++++++++++++++
+
+On standard Arduino boards, GPIO is by default either a function 
+like Serial or in INPUT mode.
+
+On XMC boards the inputs are UNDEFINED, you MUST specify every pin 
+to be in INPUT Mode that needs Inputs.
+
+
+Wire/I2C Differences
++++++++++++++++++++++
+
+The method in Wire class for 'begin' is not the same as AVR Arduino, 
+and has different modes for Master and Slave
+
+In AVR Arduino setting an I2C Master or Slave
+
+.. code-block:: 
+
+     Wire.begin(8); // join i2c bus (address optional for master)
+
+XMC-for-Arduino setting for I2C Master ONLY
+
+.. code-block:: 
+
+        Wire.begin(); // join i2c bus (address blank for master)
+
+Currently the address is NOT optional for XMC as this currently assumes this
+must be Slave mode configuration and sets the I2C configuration differently.
+
+Tone
+++++++
+
+Number of Tone pins is determined by pins_arduino.h define NUM_TONE_PINS. 
+This allows for use in other modules and for variations between boards as 
+>100MHz boards can obviously handle more tone pins.
+
+The default for XMC1xxx is 4 with a change XMC4xxxx should be 16
+
+Tone has frequency range of maximum = 500 Hz minimum = 1 Hz
+
+This is due to the fact that the tone frequency is software derived from 
+the Systick handler, Systick has a time period of 1 ms. At maximum each 
+handler event for Systick toggles a GPIO pin, so at minimum period of 1 ms 
+the output is toggled, so TWO events produce one square wave cycle, therefore 
+the maximum output frequency is 500Hz.
+
+The minimum is due to the fact that tone function only accepts an unsigned 
+integer (32 bit) for the frequency, so the minimum usable frequency is 1.
+
+Standard Arduino boards use hardware timers (the few that are available) to 
+generate tones and at least one timer can interfere with other functions.
+
+However this does mean you can have more tone pins, just much lower frequency range.
+
+
+Analog Functions and improvements
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+wiring_analog after V1.2.1
+-----------------------------
+Analog functions like analogRead and analogWrite etc. have changed after 
+V1.2.1 to have extra safety measures to ensure invalid settings cannot be 
+done and report errors.
+
+Additionally extra getter functions have been added so other libraries can 
+access the resolution of read and write functions as number of bits and 
+current maximum value possible.
+
+
+Extra functions
+----------------
+
+These functions return the analogue resolution as number of bits
+
+* uint8_t getAnalogReadBits( ) - range 8 to 12
+* uint8_t getAnalogWriteBits( ) - range 8 to 16
+
+These functions return the analogue resolution as its maximum value
+
+* uint16_t getAnalogReadMaximum( ) - range 255 to 4095
+* uint16_t getAnalogWriteMaximum( ) - range 255 to 65535
+
+This function enables the analog amplifiers at the ADC inputs with 
+adjustible gain (for XMC1000 series)
+
+* uint32_t analogRead_variableGain( uint8_t channel, uint8_t gain_value )     
+
+The gain factor values can be found :ref:`here <gain_factor>`.
+
+
+Default Values
+----------------
+
+Read resolution default is 10 bits (0 to 1023)
+
+Write resolution default is 8 bits (0 to 255)
+
+
+Error and Return Codes by Function
+-----------------------------------
+
+Where possible functions do :command:`NOT` action invalid parameters passed in.
+
+Functions return error codes or valid values so be sure which error 
+code you are looking for as some functions can return 0 as a valid 
+value (e.g. analogRead) so an out of range value is returned instead.
+
+.. list-table:: 
+    :header-rows: 1
+
+    * - Function
+      - Valid Return
+      - Errors
+    * - analogReadResolution	
+      - | 8 to 12
+        | as passed in	
+      - 255
+    * - getAnalogReadBits	
+      - 8 to 12
+      -	none
+    * - getanalogReadMaximum	
+      - 255 to 4095
+      -	none
+    * - analogWriteResolution
+      - | 8 to 16
+        | as passed in	
+      - 255
+    * - getAnalogWriteBits	
+      - 8 to 16	
+      - none
+    * - getanalogWriteMaximum	
+      - 255 to 65535	
+      - none
+    * - analogRead	
+      - 0 to Maximum for Resolution	
+      - | 0xFFFFFFFF usually 
+        | invalid channel
+    * - analogWrite	
+      - 0 success	
+      - | -1 = invalid value
+        | -2 = wrong pin
+    * - setAnalogWriteFrequency
+      - 0 success	
+      - | -1 = invalid frequency
+        | -2 = wrong pin
+    * - analogReference	
+      - none	
+      - NULL function see below
+
+This should enable checks in software for valid operation 
+and debugging problem code.
+
+AREF Analogue Reference
+------------------------
+
+On all boards the Analogue Reference is set to use the internal power supply 
+(however noisy), so the AREF pin is an :command:`OUTPUT` of the AREF in use. 
+Do :command:`NOT` connect any external voltage source to this pin, or use 
+shields that change this voltage.
+
+:command:`CAUTION` any shorts on this pin especially to 0V (GND) will bring 
+down the supply 
+of the chip.
+
+The pin voltage is the current supply voltage to AREF for analogue conversions.
+
+This pin :command:`CANNOT` be reassigned as GPIO (pinMode has no effect).
+
+:command:`analogReference( )`
+
+This function has NO operation and will not match any call on parameters 
+passed in with other libraries or examples that use this call.
+
+Any shields and examples that try to change this, will :command:`NOT` function 
+the same on these boards.
+
+
+Analog amplifiers at the ADC inputs with adjustible gain
+----------------------------------------------------------
+Each analog input channel can be configured to be amplified by an adjustable 
+gain factor, for XMC1000 series. To configure the gain, the gain value is to 
+be selected in the analogRead_variableGain() function which translates to a 
+gain factor as per the following table:
+
+
+.. _gain_factor:
+
+.. list-table:: 
+    :header-rows: 1
+
+    * - Gain value
+      - Gain factor
+    * - 0
+      - 1
+    * - 1
+      - 3
+    * - 2 
+      - 6
+    * - 3 
+      - 12
+
+For more information, please refer to the application note 
+`here <https://www.infineon.com/dgdl/Infineon-VADC-XMC1200_XMC1300-AP32304-AN-v01_10-EN.pdf?fileId=5546d4624e765da5014ed981f63136d6>`_.
+
+I2C Analog pins
+^^^^^^^^^^^^^^^^^
+
+Arduino Uno R3 format dictates that A4 and A5 are also used 
+for I2C operations, so when I2C is enabled analogue inputs A4 
+and A5 are NOT available.
+
+On Arduino Uno R3 this is an alternate pin function, depending 
+on which XMC-for-Arduino boards this could be an alternate pin 
+function, or other case as described below.
+
+
+.. list-table:: 
+    :header-rows: 1
+
+    * - Board
+      - Functionality
+      - Note
+    * - XMC1100 Boot Kit
+      - NOT supported
+      - | A4 + A5 are separate
+        | A6 + A7 are alternate pin 
+        | configurations to I2C
+    * - XMC1300 Boot Kit
+      - | NOT same pin format
+        | as Arduino Uno R3
+      - | A10 + A11 are alternate pin
+        | configurations to I2C
+    * - XMC1400 Arduino Kit
+      - Alternate pin function
+      - Matches Arduino Uno  
+    * - XMC4400 Platform 2Go
+      - External hard wired pins
+      - | For 3V3 boards set I2C pins to tristate or open drain to use
+        | For 5V boards see Wiki board page on track cuts to enable A4 and A5 to work
+        | Level shifter on the 5V board could interfere with tristate/open drain setting
+    * - XMC4700 Relax Kit (and variants)
+      - External hard wired pins
+      - | For 3V3 boards set I2C pins to tristate or open drain to use
+        | For 5V boards see Wiki board page on track cuts to enable A4 and A5 to work
+        | Level shifter on the 5V board could interfere with tristate/open drain setting
+
+
+Serial selection
+^^^^^^^^^^^^^^^^^^
+
+Serial Output Selection
+-------------------------
+On the XMC boards, two kinds of serial outputs are possible, namely:
+
+* SERIAL DEBUG (via PC)
+* SERIAL ONBOARD
+
+If these two outputs share the same instance of the internal USIC channel, 
+only one of the two could be used at a given time. The selection can be made 
+via the Tools menu as shown in the picture below.
+
+.. image:: img/serial_selection.png
+    :width: 600
+
+This is generally the case for most of the XMC boards. However, for boards 
+such as the :ref:`xmc4200-platform2go` and the :ref:`xmc4700-relax`, both the serial 
+output modes are simultaneously active and neednot be selected or enabled from the menu.
+
+Note: Please note that the sketch must be recompiled when a different serial 
+output is selected.
+
+:command:`For advanced users`
+The build flag -DSERIAL_HOSTPC must be used for the serial output interface 
+via PC and the build flag -DSERIAL_ONBOARD must be used for serial output 
+through the onboard TX and RX pins