Supported Devices

This page outlines the microcontrollers that are supported for use with EX‑IOExpander, including outlining the pins available for use.

When uploading the EX‑IOExpander software, the device type is detected by the compiler in either the Arduino IDE or PlatformIO, so no configuration is necessary on the EX‑IOExpander device itself (aside from the I²C address of course).

All allocation of pins is done via the device driver (see EX-CommandStation device driver).

Note

When configuring the device driver, all available pins must be accounted for as either digital or analogue pins, even if there is no intended use for every individual pin.

Arduino Nano

Table 21 Arduino Nano pin allocations

Total pins 18	Minimum	Maximum
Digital pins	12	16
Analogue pins	2	6

Note

On Arduino Nano, the additional analogue pins A6/7 are analogue only can cannot be used as digital inputs or outputs.

Table 22 Arduino Nano and Pro Mini EX-IOExpander pin map at Vpin 800

Vpins	800	801	802	803	804	805
Digital Pins	D2	D3	D4	D5	D6	D7
Vpins	806	807	808	809	810	811
Digital Pins	D8	D9	D10	D11	D12	D13
Vpins	812	813	814	815	816	817
Analogue Pins	A0	A1	A2	A3	A6	A7

Arduino Pro Mini

The Arduino Pro Mini comes in two variations; a 3.3V running at 8MHz, and a 5V running at 16MHz.

Warning

The 8MHz 3.3V Pro Mini is not 5V tolerant

The Pro Mini uses an identical pin map to the Arduino Nano.

Arduino Uno

Table 23 Arduino Uno pin allocations

Total pins 16	Minimum	Maximum
Digital pins	12	16
Analogue pins	0	4

Table 24 Arduino Uno EX-IOExpander pin map at Vpin 800

Vpins	800	801	802	803	804	805
Digital Pins	D2	D3	D4	D5	D6	D7
Vpins	806	807	808	809	810	811
Digital Pins	D8	D9	D10	D11	D12	D13
Vpins	812	813	814	815
Analogue Pins	A0	A1	A2	A3

Arduino Mega2560

Table 25 Arduino Mega pin allocations

Total pins 62	Minimum	Maximum
Digital pins	46	62
Analogue pins	0	16

Table 26 Arduino Mega EX-IOExpander pin map at Vpin 800

Vpins	800	801	802	803	804	805	806	807	808	809
Digital Pins	D2	D3	D4	D5	D6	D7	D8	D9	D10	D11
Vpins	810	811	812	813	814	815	816	817	818	819
Digital Pins	D12	D13	D14	D15	D16	D17	D18	D19	D22	D23
Vpins	820	821	822	823	824	825	826	827	828	829
Digital Pins	D24	D25	D26	D27	D28	D29	D30	D31	D32	D33
Vpins	830	831	832	833	834	835	836	837	838	839
Digital Pins	D34	D35	D36	D37	D38	D39	D40	D41	D42	D43
Vpins	840	841	842	843	844	845
Digital Pins	D44	D45	D46	D47	D48	D49
Vpins	846	847	848	849	850	851	852	853	854	855
Analogue Pins	A0	A1	A2	A3	A4	A5	A6	A7	A8	A9
Vpins	856	857	858	859	860	861
Analogue Pins	A10	A11	A12	A13	A14	A15

STMicroelectronics NUCLEO-F411RE

Warning

Support for the F411RE is experimental at best right now. While the software compiles and it appears to operate normally, no actual I/O testing has been performed.

The Nucleo F411RE is a 3v3 microcontroller with more available I/O pins than an Arduino Uno. The pin numbers used are defined using the Morpho pin names, in ascending order of the pin number for each Morpho connector, hence the pin names aren’t sequential.

Numerous I/O pins are connected to other devices or perform multiple functions which result in pin conflicts, so the only pins included are those that are able to successfully be set to input mode on startup.

Note

PC13 has a switch (blue button) with pullup resistor attached, so this is suitable as an input only (without pullups enabled) unless you disconnect SB17.

In addition, PA5 is the green LED.

Table 27 NUCLEO-F411RE pin allocations

Total pins 40	Minimum	Maximum
Digital pins	26	40
Analogue pins	0	14

Table 28 F411RE EX-IOExpander pin map at Vpin 800

Vpins	800	801	802	803	804	805	806
CN7 Digital Pins	PC10	PC11	PC12	PD2	PA15	PB7	PC13
Vpins	807	808	809	810	811	812	813	814	815	816
CN10 Digital Pins	PC9	PC8	PC6	PA12	PA11	PB12	PB6	PC7	PA9	PB2
Vpins	817	818	819	820	821	822	823	824	825
CN10 Digital Pins	PA8	PB10	PB15	PB4	PB14	PB5	PB13	PB3	PA10
Vpins	826	827	828	829	830	831	832	833
CN7 Analogue Pins	PA0	PA1	PA4	PB0	PC2	PC1	PC3	PC0
Vpins	834	835	836	837	838	839
CN10 Analogue Pins	PC5	PA5	PA6	PA7	PB1	PC4

STMicroelectronics NUCLEO-F412ZG

Warning

Support for the F412ZG is experimental at best right now. While the software compiles and it appears to operate normally, no actual I/O testing has been performed.

The Nucleo F412ZG is a 3v3 microcontroller with significantly more available I/O pins than an Arduino Mega. The pin numbers used are defined using the Morpho pin names, in ascending order of the pin number for each Morpho connector, hence the pin names aren’t sequential.

Numerous I/O pins are connected to other devices or perform multiple functions which result in pin conflicts, so the only pins included are those that are able to successfully be set to input mode on startup.

Note

PC13 has a switch (blue button) with pullup resistor attached, so this is suitable as an input only (without pullups enabled) unless you disconnect SB17.

In addition, PB0 is the green LED, PB7 is the blue LED, and PB14 in the red LED.

Table 29 NUCLEO-F412ZG pin allocations

Total pins 97	Minimum	Maximum
Digital pins	81	97
Analogue pins	0	16

Table 30 F412ZG EX-IOExpander pin map at Vpin 800

Vpins	800	801	802	803	804	805	806	807	808	809
CN11 Digital Pins	PC10	PC11	PC12	PD2	PF6	PF7	PA15	PB7	PC13	PD4
Vpins	810	811	812	813	814	815	816	817	818	819
CN11 Digital Pins	PD3	PD5	PG2	PD6	PG3	PD7	PE2	PE3	PE4	PE5
Vpins	820	821	822	823	824	825	826	827	828	829
CN11 Digital Pins	PF1	PF2	PF0	PF8	PD1	PF9	PD0	PG1	PG0	PE1
Vpins	830	831	832	833	834	835	836
CN11 Digital Pins	PE6	PG9	PG15	PG12	PG10	PG13	PG11
Vpins	837	838	839	840	841	842	843	844	845	846
CN12 Digital Pins	PC9	PC8	PC6	PB12	PB6	PB11	PC7	PB2	PB10	PB15
Vpins	847	848	849	850	851	852	853	854	855	856
CN12 Digital Pins	PB4	PB14	PB5	PB13	PB3	PF5	PF4	PE8	PD13	PF10
Vpins	857	858	859	860	861	862	863	864	865	866
CN12 Digital Pins	PD12	PE7	PD11	PD14	PE10	PD15	PE12	PF14	PE14	PE9
Vpins	867	868	869	870	871	872	873	874	875	876
CN12 Digital Pins	PE15	PE13	PE11	PF13	PF3	PF12	PF15	PG14	PF11	PE0
Vpins	877	878	879	880
CN12 Digital Pins	PD10	PG8	PG5	PG4
Vpins	881	882	883	884	885	886	887	888
CN11 Analogue Pins	PA0	PA1	PA4	PB0	PC2	PC1	PC3	PC0
Vpins	889	890	891	892	893	894	895	896
CN12 Analogue Pins	PC5	PA5	PA6	PA7	PB1	PC4	PA2	PA3

Arduino Zero (or SAMD based clone)

Warning

The Arduino Zero (and SAMD based clones) are 3v3 only and are not 5V tolerant.

Support for the Arduino Zero (or other SAMD clones) is experimental at best right now. While the software compiles and it appears to operate normally, no actual I/O testing has been performed.

Table 31 Arduino Zero pin allocations

Total pins 27	Minimum	Maximum
Digital pins	21	27
Analogue pins	0	6

Table 32 Arduino Zero EX-IOExpander pin map at Vpin 800

Vpins	800	801	802	803	804	805	806	807
Digital Pins	0	1	2	3	4	5	6	7
Vpins	808	809	810	811	812	813	814	815
Digital Pins	8	9	10	11	12	13	22	23
Vpins	812	813	814	815	816
Digital Pins	24	38	39	40	41
Vpins	817	818	819	820	821	822
Analogue Pins	A0	A1	A2	A3	A5	A6

Adding new devices

Warning

When considering adding new devices to EX‑IOExpander, be sure to take into account whether they are 5V or 3.3V devices, and whether their I/O and I²C pins are 5V tolerant if they are 3.3V devices. New generation microcontrollers tend to be 3.3V, and some have 5V tolerant I/O pins (eg. STM32 Nucleo), but some are not 5V tolerant (eg. SAMD).

To connect 3.3V devices to a 5V EX‑CommandStation, they need to either be 5V tolerant, or you will need to use a level shifter to avoid letting the magic smoke out.

Adding new devices to the EX‑IOExpander software is fairly straight forward, and only requires additional information in the EX‑IOExpander software itself, with no changes required to the device driver loaded in your EX‑CommandStation.

In order to successfully add an additional device, you need to know the C++ preprocessor macro definitions for the architecture or platform, and for the specific variant or board itself. In addition, you need to specify how the Vpins defined in the device driver map to the physical pins of the EX‑IOExpander device.

For example, the AVR series (Uno, Mega, Nano) have the architure or platform macro defined as “ARDUINO_ARCH_AVR”, with the Nano having the variant or board specific macro “ARDUINO_AVR_NANO”, and there is a pin map defined that maps to this macro definition.

Enabling software reboots

The architecture or platform macro is used to determine the correct method to reboot the device via the <Z> command, whereas the variant or board specific macro is used to define the actual pins in use.

If a new architecture or platform is being added, then “EX-IOExpander.ino” will need to be updated with the suitable software command in the “reset()” function, otherwise a reboot via <Z> will not be available.

If the architecture or platform already exists, or there is no desire to reboot via software, then the only change required is to add the variant or board specific information to “SupportedDevices.h”.

Enabling serial input/output

Some microcontrollers have different serial implementations, and therefore it may be necessary to specify the type of USB or serial port in use.

Currently, unless the device’s architecture is defined as “ARDUINO_ARCH_SAMD”, it will utilise the default Arduino “Serial” implementation. SAMD uses the “SerialUSB” implementation.

If additional serial support is required, this will need to be defined in “EX-IOExpander.ino” as “USB_SERIAL”, which is defined at the beginning of the file.

Defining the device and pin map in SupportedDevices.h

A pin map is used to map the Vpins from the device driver in the EX‑CommandStation to the appropriate physical pins on the EX‑IOExpander device, and therefore defining this in the correct order in the EX‑IOExpander software is critical. It is equally critical to ensure that the correct variant or board macro is used to ensure the correct pin map is used when compiling and uploading the software to the EX‑IOExpander device.

Pin maps are defined in the file “SupportedDevices.h”.

As per Pin/Vpin allocation, digital pins are allocated first, incrementing from the first Vpin, and analogue pins are allocated in reverse, starting from the last Vpin.

These are the considerations when defining the pin map:

• All pins capable of being digital inputs/outputs need to be included in “digitalPinMap”, including analogue capable pins

• All pins capable of being analogue inputs need to be included in “analoguePinMap” (don’t include dual digital/analogue pins here)

• Pins included in both pin maps need to be in the same order, with analogue pins at the end of the digital pin map

• Macros for the number of pins in each pin map must be defined accurately

• NUMBER_OF_DIGITAL_PINS is the number of digital only pins

• NUMBER_OF_ANALOGUE_PINS is the number of pins capable of analogue input, whether or not they can be used as digital also

• Any pins that are only capable of analogue inputs must be at the end of the analogue pin map

Further to this, if EEPROM is available, this needs to be defined, along with a description that is presented in the serial console when starting the device.

If the microcontroller utilises internal I²C pullup resistors rather than external, physical resistors, then the I²C pins can be defined to allow these to be disabled via “myConfig.h” (see DISABLE_I2C_PULLUPS).

To use the Arduino Nano as the example, this is the definition in “SupportedDevices.h”:

// Arduino Nano
#elif defined(ARDUINO_AVR_NANO)
#define BOARD_TYPE F("Nano")
#define HAS_EEPROM
#define NUMBER_OF_DIGITAL_PINS 12   // D2 - D13
#define NUMBER_OF_ANALOGUE_PINS 6     // A0 - A3, A6/A7, cannot use A4/A5
static const uint8_t digitalPinMap[NUMBER_OF_DIGITAL_PINS + NUMBER_OF_ANALOGUE_PINS] = {
  2,3,4,5,6,7,8,9,10,11,12,13,A0,A1,A2,A3
};
static const uint8_t analoguePinMap[NUMBER_OF_ANALOGUE_PINS] = {
  A0,A1,A2,A3,A6,A7
};
#define I2C_SDA A4
#define I2C_SCL A5

• The variant or board macro definition is “ARDUINO_AVR_NANO”.

• The “BOARD_TYPE” is displayed in the serial console at startup as “Nano”.

• The Nano has EEPROM support to allow storing the I²C address

• There are 12 digital pins

• There are 6 analogue pins

• All digital pins and the 4 analogue pins capable of digital are defined in “digitalPinMap”

• All analogue pins are defined in “analoguePinMap”

• The analogue pins defined in both pin maps are added in the same order, with analogue pins at the end of the digital pin map

• Analogue pins A6/A7 are analogue only, are therefore not included in digitalPinMap, and are defined at the end of analoguePinMap

• Arduino Nano uses internal I²C pullup resistors, and therefore defining the I²C pins A4/A5 allows these to be disabled via “myConfig.H” if desired