Added more Serial, SPI, and WIRE instances to MT-D21E (rev A and B). Documentation updates.

Author: mattairtech

CHANGELOG

@@ -1,3 +1,16 @@
+1.6.8-beta-b2:
+* Added more Serial, SPI, and WIRE options
+* Added MicroSD card firmware loading in the bootloader
+* Fixed SDU library to work with MattairTech boards
+* Fixed auto-detection for Arduino Zero and M0 board variants
+* Documentation updates
+* Merged in changes from upstream SAMD CORE 1.6.15:
+  * 
+
+1.6.8-beta-b1:
+* Fixed auto-reset not working on some versions of Windows
+* Documentation updates
+
 1.6.8-beta-b0:
 * Added L21 and C21 support. Improved D11D and D11C support.
   * Use Tools->Microcontroller menu to select mcu.

README.md

@@ -72,13 +72,14 @@ Analog Outputs	| One 10-bit (two 12-bit on L21)	| One 10-bit (two 12-bit on L21)
 PWM Outputs	| 18					| 14					| 14					| 8 (6 for 14-pin)
 Interrupts	| 16					| 16					| 16					| 8 (7 for 14-pin)
 USB		| Full Speed Device and Host (not C21)	| Full Speed Device and Host (not C21)	| Full Speed Device and Host (not C21)	| Full Speed Device
-SERCOM		| 6					| 6					| 4					| 3 (2 for 14-pin)
-UART (Serial)	| Up to 3				| Up to 3				| Up to 2				| Up to 2
-SPI		| Up to 3				| Up to 2				| 1					| 1
-I2C (WIRE)	| Up to 3				| Up to 2				| 1					| 1
+SERCOM*		| 6					| 6					| 4					| 3 (2 for 14-pin)
+UART (Serial)*	| Up to 6				| Up to 6				| Up to 4				| Up to 2
+SPI*		| Up to 3				| Up to 2				| Up to 2				| Up to 1
+I2C (WIRE)*	| Up to 3				| Up to 2				| Up to 2				| Up to 1
 I2S		| Present on the D21 only		| Present on the D21 only		| Present on the D21 only		| Not present
 Voltage		| 1.62V-3.63V (2.7V-5.5V for the C21)	| 1.62V-3.63V (2.7V-5.5V for the C21)	| 1.62V-3.63V (2.7V-5.5V for the C21)	| 1.62V-3.63V
 I/O Pin	Current	| D21: 7mA, L21: 5mA, C21: 6mA@5V	| D21: 7mA, L21: 5mA, C21: 6mA@5V	| D21: 7mA, L21: 5mA, C21: 6mA@5V	| 7 mA
+* Note that the maximum number of UART/SPI/I2C is the number of SERCOM. The number listed above for UART/SPI/I2C indicated how many are configurable through the Arduino IDE menu.
 
 
 
@@ -153,10 +154,17 @@ Choose NO_BOOTLOADER if not using a bootloader (an external programmer will be u
 
 ### Serial Config Menu
 
-This menu is used to select different combinations of serial peripherals. This is useful especially for
-the D11, which has a reduced pin count and number of SERCOMs. It can also be used to reduce FLASH and
-SRAM usage by selecting fewer UART peripherals, which are instantiated in the core, rather than only
-when including a library (like SPI and WIRE). Most board variants support two UART as an option.
+This menu is used to select different combinations of serial peripherals. It adds additional UART, SPI,
+and WIRE instances. This is also useful for the D11, which has a reduced pin count and number of SERCOMs.
+It can also be used to reduce FLASH and SRAM usage by selecting fewer UART peripherals, which are
+instantiated in the core, rather than only when including a library (like SPI and WIRE). Note that with
+options where there is more than one SPI or WIRE, the additional instances will consume a small amount
+of RAM, but neither the peripheral nor the pins are configured until begin() method is called (thus, the
+pins can be used for other purposes).
+
+Use the ASCII art rendering at the top of the README.md file of the board variant used in order to
+determine the mapping of instances to pins. When USB CDC is enabled, Serial refers to SerialUSB,
+otherwise it refers to Serial1 (TX1/RX1).
 
 
 ### USB Config Menu
@@ -458,6 +466,8 @@ OS X support currently in beta (see below), the following instructions are only
 
 ### SAM M0+ Core Installation
 
+**See Beta Builds section below to install the beta, as it uses a different json file**
+
 * To update from a previous version, click on MattairTech SAM M0+ Boards in Boards Manager, then click Update.
 
 1. The MattairTech SAM M0+ Core requires Arduino 1.6.7 or above (including 1.8.x).
@@ -516,7 +526,7 @@ several features, including three new commands (Arduino Extended Capabilities) t
 bootloader normally requires 8 KB FLASH, however, a 4 KB version can be used for the D11 chips.
 
 Bossac is a command line utility for uploading firmware to SAM-BA bootloaders. It runs on Windows. Linux, and OS X.
-It is used by Arduino to upload firmware to SAM and SAM M0+ boards. The version Bossac described here adds to the
+It is used by Arduino to upload firmware to SAM and SAM M0+ boards. The version described here adds to the
 Arduino version (https://github.com/shumatech/BOSSA, Arduino branch), which in turn is a fork from the original
 Bossa (http://www.shumatech.com/web/products/bossa). It adds support for more SAM M0+ chips (D21, L21, C21, and D11).
 
@@ -687,13 +697,15 @@ from the MT-D11 variant.
 
 
 
-## Possible Future Additions/Changes
+## Future Additions/Changes
 
-* Timer library is currently under development (like TimerOne, plus input capture, plus ??)
-* OS X support currently in beta testing
-* Reduce SRAM usage by USB endpoint buffers by only allocating endpoints actually used (D11 especially)
+### In-Progress
+* Timer library (like TimerOne, plus input capture, plus ??)
 * Drivers for MT-D21E optional memory devices (SRAM, FLASH, EEPROM)
+* OS X support currently in beta testing
 
+### Possible Future
+* Reduce SRAM usage by USB endpoint buffers by only allocating endpoints actually used (D11 especially)
 * USB Host mode CDC ACM (partially complete; BSD-like license?)
 * Features for lower power consumption (library?)
 * Reliability and security enhancements
@@ -753,6 +765,9 @@ The Changelog has moved to a separate file named CHANGELOG. The most recent chan
 
 * Boards Manager must be opened twice to see some updates (only applies to some old IDE versions)
 
+* **Boards manager might not install/uninstall the core or tools properly if the contents of the arduino15 directory has been manually modified**
+  * Be sure to delete all manually installed folders (not just files)
+
 
 ## Bugs or Issues
 

boards.txt

@@ -151,14 +151,34 @@ mattairtech_mt_d21e_revb.menu.serial.one_uart=ONE_UART_ONE_WIRE_ONE_SPI
 mattairtech_mt_d21e_revb.menu.serial.one_uart.build.serialcom_uart=ONE_UART
 mattairtech_mt_d21e_revb.menu.serial.one_uart.build.serialcom_wire=ONE_WIRE
 mattairtech_mt_d21e_revb.menu.serial.one_uart.build.serialcom_spi=ONE_SPI
+mattairtech_mt_d21e_revb.menu.serial.one_uart_one_wire_two_spi=ONE_UART_ONE_WIRE_TWO_SPI
+mattairtech_mt_d21e_revb.menu.serial.one_uart_one_wire_two_spi.build.serialcom_uart=ONE_UART
+mattairtech_mt_d21e_revb.menu.serial.one_uart_one_wire_two_spi.build.serialcom_wire=ONE_WIRE
+mattairtech_mt_d21e_revb.menu.serial.one_uart_one_wire_two_spi.build.serialcom_spi=TWO_SPI
+mattairtech_mt_d21e_revb.menu.serial.one_uart_two_wire_one_spi=ONE_UART_TWO_WIRE_ONE_SPI
+mattairtech_mt_d21e_revb.menu.serial.one_uart_two_wire_one_spi.build.serialcom_uart=ONE_UART
+mattairtech_mt_d21e_revb.menu.serial.one_uart_two_wire_one_spi.build.serialcom_wire=TWO_WIRE
+mattairtech_mt_d21e_revb.menu.serial.one_uart_two_wire_one_spi.build.serialcom_spi=ONE_SPI
 mattairtech_mt_d21e_revb.menu.serial.two_uart=TWO_UART_ONE_WIRE_ONE_SPI
 mattairtech_mt_d21e_revb.menu.serial.two_uart.build.serialcom_uart=TWO_UART
 mattairtech_mt_d21e_revb.menu.serial.two_uart.build.serialcom_wire=ONE_WIRE
 mattairtech_mt_d21e_revb.menu.serial.two_uart.build.serialcom_spi=ONE_SPI
-mattairtech_mt_d21e_revb.menu.serial.no_uart=NO_UART_ONE_WIRE_ONE_SPI
+mattairtech_mt_d21e_revb.menu.serial.three_uart_one_wire_no_spi=THREE_UART_ONE_WIRE_NO_SPI
+mattairtech_mt_d21e_revb.menu.serial.three_uart_one_wire_no_spi.build.serialcom_uart=THREE_UART
+mattairtech_mt_d21e_revb.menu.serial.three_uart_one_wire_no_spi.build.serialcom_wire=ONE_WIRE
+mattairtech_mt_d21e_revb.menu.serial.three_uart_one_wire_no_spi.build.serialcom_spi=NO_SPI
+mattairtech_mt_d21e_revb.menu.serial.three_uart_no_wire_one_spi=THREE_UART_NO_WIRE_ONE_SPI
+mattairtech_mt_d21e_revb.menu.serial.three_uart_no_wire_one_spi.build.serialcom_uart=THREE_UART
+mattairtech_mt_d21e_revb.menu.serial.three_uart_no_wire_one_spi.build.serialcom_wire=NO_WIRE
+mattairtech_mt_d21e_revb.menu.serial.three_uart_no_wire_one_spi.build.serialcom_spi=ONE_SPI
+mattairtech_mt_d21e_revb.menu.serial.four_uart=FOUR_UART_NO_WIRE_NO_SPI
+mattairtech_mt_d21e_revb.menu.serial.four_uart.build.serialcom_uart=FOUR_UART
+mattairtech_mt_d21e_revb.menu.serial.four_uart.build.serialcom_wire=NO_WIRE
+mattairtech_mt_d21e_revb.menu.serial.four_uart.build.serialcom_spi=NO_SPI
+mattairtech_mt_d21e_revb.menu.serial.no_uart=NO_UART_ONE_WIRE_TWO_SPI
 mattairtech_mt_d21e_revb.menu.serial.no_uart.build.serialcom_uart=NO_UART
 mattairtech_mt_d21e_revb.menu.serial.no_uart.build.serialcom_wire=ONE_WIRE
-mattairtech_mt_d21e_revb.menu.serial.no_uart.build.serialcom_spi=ONE_SPI
+mattairtech_mt_d21e_revb.menu.serial.no_uart.build.serialcom_spi=TWO_SPI
 mattairtech_mt_d21e_revb.menu.usb.cdc=CDC_ONLY
 mattairtech_mt_d21e_revb.menu.usb.cdc.build.usbcom=CDC_ONLY
 mattairtech_mt_d21e_revb.menu.usb.cdc.build.pid=0x0557
@@ -261,14 +281,34 @@ mattairtech_mt_d21e.menu.serial.one_uart=ONE_UART_ONE_WIRE_ONE_SPI
 mattairtech_mt_d21e.menu.serial.one_uart.build.serialcom_uart=ONE_UART
 mattairtech_mt_d21e.menu.serial.one_uart.build.serialcom_wire=ONE_WIRE
 mattairtech_mt_d21e.menu.serial.one_uart.build.serialcom_spi=ONE_SPI
+mattairtech_mt_d21e.menu.serial.one_uart_one_wire_two_spi=ONE_UART_ONE_WIRE_TWO_SPI
+mattairtech_mt_d21e.menu.serial.one_uart_one_wire_two_spi.build.serialcom_uart=ONE_UART
+mattairtech_mt_d21e.menu.serial.one_uart_one_wire_two_spi.build.serialcom_wire=ONE_WIRE
+mattairtech_mt_d21e.menu.serial.one_uart_one_wire_two_spi.build.serialcom_spi=TWO_SPI
+mattairtech_mt_d21e.menu.serial.one_uart_two_wire_one_spi=ONE_UART_TWO_WIRE_ONE_SPI
+mattairtech_mt_d21e.menu.serial.one_uart_two_wire_one_spi.build.serialcom_uart=ONE_UART
+mattairtech_mt_d21e.menu.serial.one_uart_two_wire_one_spi.build.serialcom_wire=TWO_WIRE
+mattairtech_mt_d21e.menu.serial.one_uart_two_wire_one_spi.build.serialcom_spi=ONE_SPI
 mattairtech_mt_d21e.menu.serial.two_uart=TWO_UART_ONE_WIRE_ONE_SPI
 mattairtech_mt_d21e.menu.serial.two_uart.build.serialcom_uart=TWO_UART
 mattairtech_mt_d21e.menu.serial.two_uart.build.serialcom_wire=ONE_WIRE
 mattairtech_mt_d21e.menu.serial.two_uart.build.serialcom_spi=ONE_SPI
-mattairtech_mt_d21e.menu.serial.no_uart=NO_UART_ONE_WIRE_ONE_SPI
+mattairtech_mt_d21e.menu.serial.three_uart_one_wire_no_spi=THREE_UART_ONE_WIRE_NO_SPI
+mattairtech_mt_d21e.menu.serial.three_uart_one_wire_no_spi.build.serialcom_uart=THREE_UART
+mattairtech_mt_d21e.menu.serial.three_uart_one_wire_no_spi.build.serialcom_wire=ONE_WIRE
+mattairtech_mt_d21e.menu.serial.three_uart_one_wire_no_spi.build.serialcom_spi=NO_SPI
+mattairtech_mt_d21e.menu.serial.three_uart_no_wire_one_spi=THREE_UART_NO_WIRE_ONE_SPI
+mattairtech_mt_d21e.menu.serial.three_uart_no_wire_one_spi.build.serialcom_uart=THREE_UART
+mattairtech_mt_d21e.menu.serial.three_uart_no_wire_one_spi.build.serialcom_wire=NO_WIRE
+mattairtech_mt_d21e.menu.serial.three_uart_no_wire_one_spi.build.serialcom_spi=ONE_SPI
+mattairtech_mt_d21e.menu.serial.four_uart=FOUR_UART_NO_WIRE_NO_SPI
+mattairtech_mt_d21e.menu.serial.four_uart.build.serialcom_uart=FOUR_UART
+mattairtech_mt_d21e.menu.serial.four_uart.build.serialcom_wire=NO_WIRE
+mattairtech_mt_d21e.menu.serial.four_uart.build.serialcom_spi=NO_SPI
+mattairtech_mt_d21e.menu.serial.no_uart=NO_UART_ONE_WIRE_TWO_SPI
 mattairtech_mt_d21e.menu.serial.no_uart.build.serialcom_uart=NO_UART
 mattairtech_mt_d21e.menu.serial.no_uart.build.serialcom_wire=ONE_WIRE
-mattairtech_mt_d21e.menu.serial.no_uart.build.serialcom_spi=ONE_SPI
+mattairtech_mt_d21e.menu.serial.no_uart.build.serialcom_spi=TWO_SPI
 mattairtech_mt_d21e.menu.usb.cdc=CDC_ONLY
 mattairtech_mt_d21e.menu.usb.cdc.build.usbcom=CDC_ONLY
 mattairtech_mt_d21e.menu.usb.cdc.build.pid=0x0557

variants/MT_D21E/README.md

@@ -8,17 +8,17 @@ Other  COM    PWM   Analog  INT  Arduino*             Arduino*  INT   PWM     CO
 Xin32                                | A0            RST |                           BOOT
 Xout32                               | A1            NC  |
 DAC                   *            2 | A2            NC  |
-REFA                  *            3 | A3            A31 | 31    *   TCC11         SWDIO*
-REFB                  *      *     4 | A4            A30 | 30    *   TCC10         SWDCLK
+REFA                  *            3 | A3            A31 | 31    *   TCC11   RX3   SWDIO*
+REFB                  *      *     4 | A4            A30 | 30    *   TCC10   TX3   SWDCLK
                       *      *     5 | A5            NC  |
                       *            6 | A6            A28 | 28    *                   LED
 VM                    *            7 | A7            A27 | 27    *                   BTNA
-             TCC00    *     NMI    8 | A8            A23 | 23    *   TC41     SS
-             TCC01    *      *     9 | A9            A22 | 22    *   TC40     MISO
-       TX1   TCC02    *           10 | A10           A19 | 19    *            SCK
-       RX1   TCC03    *           11 | A11           A18 | 18    *            MOSI
-       TX2   TC30            *    14 | A14           A17 | 17    *   TCC21    SCL
-       RX2   TC31                 15 | A15           A16 | 16    *   TCC20    SDA
+  SDA1/MISO1  TCC00   *     NMI    8 | A8            A23 | 23    *   TC41     SS
+   SCL1/SS1   TCC01   *      *     9 | A9            A22 | 22    *   TC40     MISO
+      TX1     TCC02   *           10 | A10           A19 | 19    *            SCK
+      RX1     TCC03   *           11 | A11           A18 | 18    *            MOSI
+   TX2/MOSI1   TC30          *    14 | A14           A17 | 17    *   TCC21    SCL/RX4
+    RX2/SCK1   TC31               15 | A15           A16 | 16    *   TCC20    SDA/TX4
                                      | NC            NC  |
                                      | NC            NC  |
                                      | Vbus          3.3V|   * Button B available on 31.
@@ -48,30 +48,30 @@ Arduino	| Silk	| Port	| Alternate Function	| Comments (! means not used with thi
 5	| A5	| PA05	|			| EIC/EXTINT[5] ADC/AIN[5] AC/AIN[1] PTC/Y[3] !SERCOM0/PAD[1] !TCC0/WO[1]
 6	| A6	| PA06	|			| !EIC/EXTINT[6] ADC/AIN[6] AC/AIN[2] PTC/Y[4] !SERCOM0/PAD[2] !TCC1/WO[0]
 7	| A7	| PA07	| Voltage Divider	| !EIC/EXTINT[7] ADC/AIN[7] AC/AIN[3] PTC/Y[5] !SERCOM0/PAD[3] !TCC1/WO[1]
-8	| A8	| PA08	|			| EIC/NMI ADC/AIN[16] PTC/X[0] !SERCOM0/PAD[0] !SERCOM2/PAD[0] TCC0/WO[0] !TCC1/WO[2]
-9	| A9	| PA09	|			| EIC/EXTINT[9] ADC/AIN[17] PTC/X[1] !SERCOM0/PAD[1] !SERCOM2/PAD[1] TCC0/WO[1] !TCC1/WO[3]
+8	| A8	| PA08	| SDA1/MISO1		| EIC/NMI ADC/AIN[16] PTC/X[0] !SERCOM0/PAD[0] SERCOM2/PAD[0] TCC0/WO[0] !TCC1/WO[2]
+9	| A9	| PA09	| SCL1/SS1		| EIC/EXTINT[9] ADC/AIN[17] PTC/X[1] !SERCOM0/PAD[1] SERCOM2/PAD[1] TCC0/WO[1] !TCC1/WO[3]
 10	| A10	| PA10	| TX1			| !EIC/EXTINT[10] ADC/AIN[18] PTC/X[2] SERCOM0/PAD[2] !SERCOM2/PAD[2] !TCC1/WO[0] TCC0/WO[2]
 11	| A11	| PA11	| RX1			| !EIC/EXTINT[11] ADC/AIN[19] PTC/X[3] SERCOM0/PAD[3] !SERCOM2/PAD[3] !TCC1/WO[1] TCC0/WO[3]
 12	| ---	| ----	| NOT A PIN		| NOT A PIN
 13	| ---	| ----	| NOT A PIN		| NOT A PIN
-14	| A14	| PA14	| Xin, TX2		| EIC/EXTINT[14] SERCOM2/PAD[2] TC3/WO[0] !TCC0/WO[4] Xin, HOST_ENABLE
-15	| A15	| PA15	| Xout, RX2		| !EIC/EXTINT[15] SERCOM2/PAD[3] TC3/WO[1] !TCC0/WO[5] Xout
-16	| A16	| PA16	| I2C/SDA w/pullup	| EIC/EXTINT[0] PTC/X[4] SERCOM1/PAD[0] !SERCOM3/PAD[0] TCC2/WO[0] !TCC0/WO[6]
-17	| A17	| PA17	| I2C/SCL w/pullup	| EIC/EXTINT[1] PTC/X[5] SERCOM1/PAD[1] !SERCOM3/PAD[1] TCC2/WO[1] !TCC0/WO[7]
-18	| A18	| PA18	| SPI MOSI		| EIC/EXTINT[2] PTC/X[6] !SERCOM1/PAD[2] SERCOM3/PAD[2] !TC3/WO[0] !TCC0/WO[2]
-19	| A19	| PA19	| SPI SCK		| EIC/EXTINT[3] PTC/X[7] !SERCOM1/PAD[3] SERCOM3/PAD[3] !TC3/WO[1] !TCC0/WO[3]
+14	| A14	| PA14	| Xin, TX2/MOSI1	| EIC/EXTINT[14] SERCOM2/PAD[2] TC3/WO[0] !TCC0/WO[4] Xin, HOST_ENABLE
+15	| A15	| PA15	| Xout, RX2/SCK1	| !EIC/EXTINT[15] SERCOM2/PAD[3] TC3/WO[1] !TCC0/WO[5] Xout
+16	| A16	| PA16	| SDA/TX4 w/pullup	| EIC/EXTINT[0] PTC/X[4] SERCOM1/PAD[0] SERCOM3/PAD[0] TCC2/WO[0] !TCC0/WO[6]
+17	| A17	| PA17	| SCL/RX4 w/pullup	| EIC/EXTINT[1] PTC/X[5] SERCOM1/PAD[1] SERCOM3/PAD[1] TCC2/WO[1] !TCC0/WO[7]
+18	| A18	| PA18	| SPI			| EIC/EXTINT[2] PTC/X[6] !SERCOM1/PAD[2] SERCOM3/PAD[2] !TC3/WO[0] !TCC0/WO[2]
+19	| A19	| PA19	| SCK			| EIC/EXTINT[3] PTC/X[7] !SERCOM1/PAD[3] SERCOM3/PAD[3] !TC3/WO[1] !TCC0/WO[3]
 20	| ---	| ----	| NOT A PIN		| NOT A PIN
 21	| ---	| ----	| NOT A PIN		| NOT A PIN
-22	| A22	| PA22	| SPI MISO		| EIC/EXTINT[6] PTC/X[10] SERCOM3/PAD[0] TC4/WO[0] !TCC0/WO[4]
-23	| A23	| PA23	| SPI SS		| EIC/EXTINT[7] PTC/X[11] SERCOM3/PAD[1] TC4/WO[1] !TCC0/WO[5]
+22	| A22	| PA22	| MISO			| EIC/EXTINT[6] PTC/X[10] SERCOM3/PAD[0] TC4/WO[0] !TCC0/WO[4]
+23	| A23	| PA23	| SS			| EIC/EXTINT[7] PTC/X[11] SERCOM3/PAD[1] TC4/WO[1] !TCC0/WO[5]
 24	| A24-	| PA24	| USB_NEGATIVE		| USB/DM TC5/WO[0]
 25	| A25+	| PA25	| USB_POSITIVE		| USB/DP TC5/WO[1]
 26	| ---	| ----	| NOT A PIN		| NOT A PIN
 27	| A27	| PA27	| Button A		| EIC/EXTINT[15] Button A
 28	| A28	| PA28	| LED			| EIC/EXTINT[8] LED
 29	| ---	| ----	| NOT A PIN		| NOT A PIN
-30	| A30	| PA30	| SWD CLK		| EIC/EXTINT[10] !SERCOM1/PAD[2] TCC1/WO[0] SWD CLK
-31	| A31	| PA31	| Button B / SWD IO	| EIC/EXTINT[11] !SERCOM1/PAD[3] TCC1/WO[1] Button B SWD IO
+30	| A30	| PA30	| SWDCLK / TX3		| EIC/EXTINT[10] SERCOM1/PAD[2] TCC1/WO[0] SWD CLK, leave floating during boot
+31	| A31	| PA31	| Button B / SWDIO / RX3| EIC/EXTINT[11] SERCOM1/PAD[3] TCC1/WO[1] Button B SWD IO
 --	| RST	| ----	|			| Reset, BOOT (double tap bootloader entry)
 ============================================================================================================================================
 
@@ -129,9 +129,9 @@ Arduino	| Silk	| Port	| Alternate Function	| Comments (! means not used with thi
 
 * **SERCOM**
   * 4 SERCOM are available.
-  * Up to 2 UART instances
-  * 1 SPI instance
-  * 1 WIRE (I2C) instance
+  * Up to 4 UART instances
+  * Up to 2 SPI instances
+  * Up to 2 WIRE (I2C) instances
   * The WIRE pullup resistors are enabled by default.