Maple Mini

This page is a general resource for information specific to the Maple Mini. The Maple Mini is a smaller version of the Maple that fits on a breadboard.

Technical Specifications

Powering the Maple Mini

You can power the Maple Mini via the USB plug or by powering Vin directly.

Warning

The silkscreen on the Maple Mini suggests it will accept an input voltage up to 16 V. We recommend applying no greater than 12 V, and potentially even lower depending upon the current draw requirements of the application. Please see Power Regulation on the Maple Mini for more information.

Power Regulation on the Maple Mini

Power regulation on the Maple is provided by two low dropout linear voltage regulators. (The part is the MCP1703 from Microchip, in the SOT-23A package. You can download the datasheet here ). One of the regulators supplies power to the digital voltage plane; the other supplies power to the analog voltage plane.

These voltage regulators nominally take an input of up to 16V. In addition, while the maximum continuous output current for the board is 250mA, if you are powering the board off higher voltages the amount current it can supply goes down, due to the regulators needing to dissipate the extra power. So if you are powering the board off 12V, the max current is about 40mA at room temperature. In general (again, at room temperature) the max power dissipation (PD) for the chip is about .37W, and output current = PD/(Vin-Vout). For exact max current calculations, please refer to the datasheet linked above.

If you are planning to draw a lot of current from the Maple board, it is necessary to provide input power as close to 3.3V as possible. Powering the microcontroller circuitry and LEDs on the board alone takes approximately 30mA, so if you are powering the board with 12V that leaves only 10mA (at best) available for powering any user circuitry. Attempting to draw more than 10mA runs the risk of shorting out the power regulators and bricking your board.

GPIO Information

The Maple Mini features 34 total input/output pins, numbered D0 through D33. These numbers correspond to the numeric values next to each header on the Maple Mini’s silkscreen. However, some of them have special uses by default [1].

Pin D23 is the USB D+ line, and D24 is the USB D- line. To use them as GPIOs, your program will need to disable SerialUSB first. Be aware, however, that disabling SerialUSB means that the bootloader won’t work properly, and you’ll need to use Perpetual Bootloader Mode to make your next upload.

Pin D32 is the Mini’s button pin. It is thus mainly useful as an input. The pin will read HIGH when the button is pressed.

Pin D33 is the Mini’s LED pin. It is thus mainly useful as an output. The LED will glow when HIGH is written to it. (It also supports PWM, for finer-grained brightness control).

Master Pin Map

This table shows a summary the available functionality on every GPIO pin, by peripheral type. The “5 V?” column documents whether or not the pin is 5 volt tolerant.

Note that this table is not exhaustive; on some pins, more peripherals are available than are listed here.

Pin GPIO ADC Timer I2C UART SPI 5 V?
D0 PB11
2_SDA 3_RX
Yes
D1 PB10
2_SCL 3_TX
Yes
D2 PB2
Yes
D3 PB0 CH8 3_CH3
D4 PA7 CH7 3_CH2
1_MOSI
D5 PA6 CH6 3_CH1
1_MISO
D6 PA5 CH5
1_SCK
D7 PA4 CH4
2_CK 1_NSS
D8 PA3 CH3 2_CH4
2_RX
D9 PA2 CH2 2_CH3
2_TX
D10 PA1 CH1 2_CH2
2_RTS
D11 PA0 CH0 2_CH1_ETR
2_CTS
D12 PC15
D13 PC14
D14 PC13
D15 PB7
4_CH2 1_SDA
Yes
D16 PB6
4_CH1 2_SCL
Yes
D17 PB5
1_SMBA
D18 PB4
Yes
D19 PB3
Yes
D20 PA15
Yes
D21 PA14
Yes
D22 PA13
Yes
D23 PA12
1_ETR
1_RTS
Yes
D24 PA11
1_CH4
1_CTS
Yes
D25 PA10
1_CH3
1_RX
Yes
D26 PA9
1_CH2
1_TX
Yes
D27 PA8
1_CH1
1_CK
Yes
D28 PB15
2_MOSI Yes
D29 PB14
3_RTS 2_MISO Yes
D30 PB13
3_CTS 2_SCK Yes
D31 PB12
1_BKIN 2_SMBA 3_CK 2_NSS Yes
D32 PB8
4_CH3
Yes
D33 PB1 CH9 3_CH4

GPIO Port Pin Map

The following table shows what pins are associated with each GPIO port.

GPIOA GPIOB GPIOC
PA0: D11 PB0: D3 PC0: -
PA1: D10 PB1: D33 PC1: -
PA2: D9 PB2: D2 PC2: -
PA3: D8 PB3: D19 PC3: -
PA4: D7 PB4: D18 PC4: -
PA5: D6 PB5: D17 PC5: -
PA6: D5 PB6: D16 PC6: -
PA7: D4 PB7: D15 PC7: -
PA8: D27 PB8: D32 PC8: -
PA9: D26 PB9: - PC9: -
PA10: D25 PB10: D1 PC10: -
PA11: D24 PB11: D0 PC11: -
PA12: D23 PB12: D31 PC12: -
PA13: D22 PB13: D30 PC13: D14
PA14: D21 PB14: D29 PC14: D13
PA15: D20 PB15: D28 PC15: D12

Timer Pin Map

The following table shows what pins are associated with a particular timer’s capture/compare channels.

Timer Ch. 1 Ch. 2 Ch. 3 Ch. 4
1 D27 D26 D25 D24
2 D11 D10 D9 D8
3 D5 D4 D3 D33
4 D16 D15 D32  

EXTI Line Pin Map

The following table shows which pins connect to which EXTI lines.

EXTI Line Pins
EXTI0 D3, D11
EXTI1 D10, D33
EXTI2 D2, D9
EXTI3 D8, D19
EXTI4 D7, D18
EXTI5 D6, D17
EXTI6 D5, D16
EXTI7 D4, D15
EXTI8 D27, D32
EXTI9 D26
EXTI10 D1, D25
EXTI11 D0, D24
EXTI12 D23, D31
EXTI13 D14, D22, D30
EXTI14 D13, D21, D29
EXTI15 D12, D20, D28

USART Pin Map

The Maple Mini has three serial ports (also known as USARTs). They communicate using the pins given in the following table.

Serial Port TX RX CK CTS RTS
Serial1 D26 D25 D27 D24 D23
Serial2 D9 D8 D7 D11 D10
Serial3 D1 D0 D31 D30 D29

Low-Noise ADC Pins

Maple Mini has an electrically isolated analog power plane with its own regulator, and a geometrically isolated ground plane, connected to the digital plane by an inductor. Its analog input pins, D3 — D11, are laid out to correspond with these analog planes, and our measurements indicate that they generally offer low noise ADC performance. However, analog performance may vary depending upon the activity of the other GPIOs. Consult the Maple Mini hardware design files for more details.

Board-Specific Values

This section lists the Maple Mini’s board-specific values.

  • CYCLES_PER_MICROSECOND: 72
  • BOARD_BUTTON_PIN: 32
  • BOARD_LED_PIN: 33
  • BOARD_NR_GPIO_PINS: 34
  • BOARD_NR_PWM_PINS: 12
  • boardPWMPins: 3, 4, 5, 8, 9, 10, 11, 15, 16, 25, 26, 27
  • BOARD_NR_ADC_PINS: 9
  • boardADCPins: 3, 4, 5, 6, 7, 8, 9, 10, 11
  • BOARD_NR_USED_PINS: 4
  • boardUsedPins: BOARD_LED_PIN, BOARD_BUTTON_PIN, 23, 24 (23 and 24 are used by USB)
  • BOARD_NR_USARTS: 3
  • BOARD_USART1_TX_PIN: 26
  • BOARD_USART1_RX_PIN: 25
  • BOARD_USART2_TX_PIN: 9
  • BOARD_USART2_RX_PIN: 8
  • BOARD_USART3_TX_PIN: 1
  • BOARD_USART3_RX_PIN: 0
  • BOARD_NR_SPI: 2
  • BOARD_SPI1_NSS_PIN: 7
  • BOARD_SPI1_MOSI_PIN: 4
  • BOARD_SPI1_MISO_PIN: 5
  • BOARD_SPI1_SCK_PIN: 6
  • BOARD_SPI2_NSS_PIN: 31
  • BOARD_SPI2_MOSI_PIN: 28
  • BOARD_SPI2_MISO_PIN: 29
  • BOARD_SPI2_SCK_PIN: 30
  • BOARD_JTMS_SWDIO_PIN: 22
  • BOARD_JTCK_SWCLK_PIN: 21
  • BOARD_JTDI_PIN: 20
  • BOARD_JTDO_PIN: 19
  • BOARD_NJTRST_PIN: 18

Hardware Design Files

The hardware schematics and board layout files are available in the Maple Mini GitHub repository.

From the GitHub repository main page, you can download the entire repository by clicking the “Download” button. If you are familiar with Git, you can also clone the repository at the command line with

$ git clone git://github.com/leaflabs/maplemini.git

Failure Modes

The following known failure modes apply to all Maple boards. The failure modes aren’t design errors, but are easy ways to break or damage your board permanently.

  • High voltage on non-tolerant pins: not all header pins are 5 V compatible; so e.g. connecting certain serial devices in the wrong way could over-voltage the pins. The pin-mapping master table details which pins are 5 V-tolerant.

Errata

This section lists known issues and warnings for the Maple Mini Rev 2 (the first Rev sold to the public).

  • Silkscreen Vin voltage mistake: The silkscreen on the Maple Mini falsely indicates that Vin may be supplied with up to 16V. We recommend an input voltage no greater than 12V, and potentially even lower depending upon the current draw requirements of the application. Please see Power Regulation on the Maple Mini for more information.