Maple Mini — Maple v0.0.12 Documentation

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# 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.

Contents

- Technical Specifications
- Powering the Maple Mini
- GPIO Information
  - Master Pin Map
  - GPIO Port Pin Map
  - Timer Pin Map
  - EXTI Line Pin Map
  - USART Pin Map
  - Low-Noise ADC Pins
- Board-Specific Values
- Hardware Design Files
- Failure Modes
- Errata
- Recommended Reading

## Technical Specifications

- MCU: STM32F103RCBT6, a 32-bit ARM Cortex M3 microprocessor
- Clock Speed: 72 MHz
- 128 KB Flash and 20 KB SRAM
- 34 digital I/ pins (GPIOs)
- 12 PWM pins at 16 bit resolution
- 9 analog input (ADC) pins at 12 bit resolution
- 2 SPI peripherals
- 2 I2C peripherals
- 7 Channels of Direct Memory Access (DMA) (dma.h)
- 3 USART (serial port) peripherals
- 1 advanced and 3 general-purpose timers
- Dedicated USB port for programming and communications
- JTAG
- Nested Vectored Interrupt Controller (NVIC) (including external interrupt on GPIOs)
- Supplies up to 500 mA at 3.3 V, with separate 250 mA digital and analog regulators for low-noise analog performance
- Open source, four layer design
- Support for low power, sleep, and standby modes (<500 μA)
- Operating Voltage: 3.3 V
- Input Voltage (recommended): 3 V — 12 V
- Dimensions: 2.02″ × 0.72″

## 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.

See this erratum for more information.

## 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 16 V. We recommend an input voltage no greater than 12 V.

  The voltage regulator on the Mini is rated up to 16 V. However, our tests indicate that as its input voltage approaches 16 V, its output begins to rise to levels higher than those recommended by ST for supplying the STM32F103CB. The limit of 12 V keeps the voltage supplied to the processor at safe levels.

## Recommended Reading

STMicro documentation for STM32F103CB microcontroller:

- Datasheet (PDF); covers STM32F103x8, STM32F103xB.
- Reference Manual RM0008 (PDF); definitive resource for peripherals on the STM32F1 line.
- Programming Manual PM0056 (PDF); assembly language and register reference.
- STM32F103CB overview page with links to further references.

Footnotes

[1] | See boardUsedPins for more information.

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