Maple RET6 Edition — Maple v0.0.10beta Documentation

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# Maple RET6 Edition

Contents

- Technical Specifications
- Powering the Maple RET6 Edition
- Using the Built-in Battery Charger
- GPIO Information
  - Master Pin Map
  - Timer Pin Map
  - EXTI Line Pin Map
  - USART Pin Map
- Board-Specific Values
- Hardware Design Files
- Failure Modes
- Errata
- Recommended Reading

## Technical Specifications

> - MCU: STM32F103RET6, a 32-bit ARM Cortex M3 microprocessor
> - Clock Speed: 72 MHz
> - 512KB Flash and 64KB SRAM
> - 43 Digital I/O Pins (GPIO)
> - 16 Analog Input pins, 12 bit ADC resolution (ADC)
> - Built-in, 2 channel DAC at 12 bit resolution (dac.h).
> - 19 PWM pins at 16-bit resolution (PWM)
> - Dedicated USB port for programming and communications (USB)
> - External JTAG interface (JTAG)
> - 64 Channel nested vector interrupt handler (including external interrupt on GPIOs)
> - Integrated SPI (SPI)
> - Integrated SDIO
> - Integrated I2C and I2S (I2C)
> - 12 Channels of Direct Memory Access (DMA) (dma.h)
> - 3 USART and 2 UART devices (USART)
> - Two advanced control, four general purpose, two basic timers (Timers)
> - Supplies up to 500mA @ 3.3v (with separate 250 mA digital and analog regulators)
> - Support for low power, sleep, and standby modes (<500uA)
> - Operating Voltage: 3.3V
> - Input Voltage (recommended): 3V-12V
> - Dimensions are 2.05″x2.1″

## Powering the Maple RET6 Edition

The Maple RET6 Edition’s power source is determined by the header to the left of the “LeafLabs” label on the silkscreen. The RET6 Edition can be powered from the barrel jack connector, USB, or a LiPo battery. We ship the RET6 Edition with a jumper on the USB selector. In order to power it off of an alternative source, unplug the board, then move the jumper to the desired selector before reconnecting power.

You can also power the Maple via the pin labeled “Vin” on the lower header. However, don’t do this while simultaneously powering the board from another source, or you could damage the board.

## Using the Built-in Battery Charger

The RET6 Edition has a built-in LiPo battery charger. In order to use it, put a jumper across the CHRG header on the power selection header and across the USB, or EXT selectors, depending on whether you’re charging the battery via USB cable or barrel jack connector. The LED labeled CHRG will light up while the battery is being charged. When the battery is finished charging, the LED labeled DONE will also light up.

## GPIO Information

The RET6 Edition features 38 ready-to-use general purpose input/output (see GPIO) pins for digital input/output, numbered `D0` through `D37`. These numbers correspond to the numeric values next to each header on the Maple silkscreen.

Pin `D38` is the board’s button pin. It is thus mainly useful as an input. The pin will read `HIGH` when the button is pressed.

More GPIOs (numbered `D39`–`D42`) are available if you use the disableDebugPorts() function; see the board-specific debug pin constants for more information. (See this erratum for information about the pin numbered `43` on the silkscreen).

### Master Pin Map

This table shows the available functionality on every GPIO pin, by peripheral type. The “STM32” column refers to the port and number that the header is connected to on the microcontroller. The “5V?” column documents whether or not the pin is 5 volt tolerant.

Pin | STM32 | ADC | Timer | I2C | UART | SPI | 5v?
--- | --- | --- | --- | --- | --- | --- | ---
D0 | PA3 | ADC3 | TIM2_CH4 |  | USART2_RX |  |
D1 | PA2 | ADC2 | TIM2_CH3 |  | USART2_TX |  |
D2 | PA0 | ADC0 | TIM2_CH1_ETR |  | USART2_CTS |  |
D3 | PA1 | ADC1 | TIM2_CH2 |  | USART2_RTS |  |
D4 | PB5 |  |  | ISC1_SMBA |  | SPI3_MOSI |
D5 | PB6 |  | TIM4_CH1 | I2C1_SCL |  |  | Yes
D6 | PA8 |  | TIM1_CH1 |  | USART1_CK |  | Yes
D7 | PA9 |  | TIM1_CH2 |  | USART1_TX |  | Yes
D8 | PA10 |  | TIM1_CH3 |  | USART1_RX |  | Yes
D9 | PB7 |  | TIM4_CH2 | I2C1_SDA |  |  | Yes
D10 | PA4 | ADC4 |  |  | USART2_CK | SPI1_NSS |
D11 | PA7 | ADC7 | TIM3_CH2 |  |  | SPI1_MOSI |
D12 | PA6 | ADC6 | TIM3_CH1 |  |  | SPI1_MISO |
D13 | PA5 | ADC5 |  |  |  | SPI1_SCK |
D14 | PB8 |  | TIM4_CH3 |  |  |  | Yes
D15 | PC0 | ADC10 |  |  |  |  |
D16 | PC1 | ADC11 |  |  |  |  |
D17 | PC2 | ADC12 |  |  |  |  |
D18 | PC3 | ADC13 |  |  |  |  |
D19 | PC4 | ADC14 |  |  |  |  |
D20 | PC5 | ADC15 |  |  |  |  |
D21 | PC13 |  |  |  |  |  |
D22 | PC14 |  |  |  |  |  |
D23 | PC15 |  |  |  |  |  |
D24 | PB9 |  | TIM4_CH4 |  |  |  | Yes
D25 | PD2 |  | TIM3_ETR |  |  | UART5_RX | Yes
D26 | PC10 |  |  |  |  | UART4_TX | Yes
D27 | PB0 | ADC8 | TIM3_CH3 |  |  |  |
D28 | PB1 | ADC9 | TIM3_CH4 |  |  |  |
D29 | PB10 |  |  | I2C2_SCL | USART3_TX |  | Yes
D30 | PB11 |  |  | I2C2_SDA | USART3_RX |  | Yes
D31 | PB12 |  | TIM1_BKIN | I2C2_SMBA | USART3_CK | SPI2_NSS | Yes
D32 | PB13 |  | TIM1_CH1N |  | USART3_CTS | SPI2_SCK | Yes
D33 | PB14 |  | TIM1_CH2N |  | USART3_RTS | SPI2_MISO | Yes
D34 | PB15 |  | TIM1_CH3N |  |  | SPI2_MOSI | Yes
D35 | PC6 |  | TIM8_CH1 |  |  |  | Yes
D36 | PC7 |  | TIM8_CH2 |  |  |  | Yes
D37 | PC8 |  | TIM8_CH3 |  |  |  | Yes
D38 | PC9 |  | TIM8_CH4 |  |  |  | Yes
D39 | PA13 |  |  |  |  |  | Yes
D40 | PA14 |  |  |  |  |  | Yes
D41 | PA15 |  |  |  |  | SPI3_NSS | Yes
D42 | PB3 |  |  |  |  | SPI3_SCK | Yes

### Timer Pin Map

The following table shows what pins are associated with a particular timer’s capture/compare channels. Note that timer 5’s channels share pins with timer 2 (e.g., timer 5 channel 1 is also available on D2, channel 2 on D3, etc.).

Timer | Ch. 1 | Ch. 2 | Ch. 3 | Ch. 4
--- | --- | --- | --- | ---
1 | D6 | D7 | D8 |
2 | D2 | D3 | D1 | D0
3 | D12 | D11 | D27 | D28
4 | D5 | D9 | D14 | D24
8 | D35 | D36 | D37 | D38

### EXTI Line Pin Map

The following table shows which pins connect to which EXTI lines on the Maple RET6 Edition.

EXTI Line | Pins
--- | ---
EXTI0 | 2, 15, 27
EXTI1 | 3, 16, 28
EXTI2 | 1, 17, 25
EXTI3 | 0, 18
EXTI4 | 10, 19
EXTI5 | 4, 13, 20
EXTI6 | 5, 12, 35
EXTI7 | 9, 11, 36
EXTI8 | 6, 14, 37
EXTI9 | 7, 25, 28
EXTI10 | 8, 26, 29
EXTI11 | 30
EXTI12 | 31
EXTI13 | 21, 32
EXTI14 | 22, 33
EXTI15 | 23, 34

### USART Pin Map

The Maple RET6 Edition has three serial ports whose pins are broken out to headers (also known as a UARTs or USARTs): `Serial1`, `Serial2`, and `Serial3`. They communicate using the pins summarized in the following table:

Serial Port | TX | RX | CK | CTS | RTS
--- | --- | --- | --- | --- | ---
`Serial1` | 7 | 8 | 6 |  |
`Serial2` | 1 | 0 | 10 | 2 | 3
`Serial3` | 29 | 30 | 31 | 32 | 33

Unfortunately, UART4 and UART5 aren’t completely available.

## Board-Specific Values

This section lists the Maple RET6 Edition’s board-specific values.

- `CYCLES_PER_MICROSECOND`: 72
- `BOARD_BUTTON_PIN`: 38
- `BOARD_LED_PIN`: 13
- `BOARD_NR_GPIO_PINS`: 44
- `BOARD_NR_PWM_PINS`: 16
- `boardPWMPins`: 0, 1, 2, 3, 5, 6, 7, 8, 9, 11, 12, 14, 24, 25, 27, 28
- `BOARD_NR_ADC_PINS`: 15
- `boardADCPins`: 0, 1, 2, 10, 11, 12, 13, 15, 16, 17, 18, 19, 20, 27, 28
- `BOARD_NR_USED_PINS`: 7
- `boardUsedPins`: `BOARD_LED_PIN`, `BOARD_BUTTON_PIN`, `BOARD_JTMS_SWDIO_PIN`, `BOARD_JTCK_SWCLK_PIN`, `BOARD_JTDI_PIN`, `BOARD_JTDO_PIN`, `BOARD_NJTRST_PIN`
- `BOARD_NR_USARTS`: 3 (unfortunately, due to the Maple Rev 5 design, UARTs 4 and 5 have pins which are not broken out)
- `BOARD_USART1_TX_PIN`: 7
- `BOARD_USART1_RX_PIN`: 8
- `BOARD_USART2_TX_PIN`: 1
- `BOARD_USART2_RX_PIN`: 0
- `BOARD_USART3_TX_PIN`: 29
- `BOARD_USART3_RX_PIN`: 30
- `BOARD_NR_SPI`: 3
- `BOARD_SPI1_NSS_PIN`: 10
- `BOARD_SPI1_MOSI_PIN`: 11
- `BOARD_SPI1_MISO_PIN`: 12
- `BOARD_SPI1_SCK_PIN`: 13
- `BOARD_SPI2_NSS_PIN`: 31
- `BOARD_SPI2_MOSI_PIN`: 34
- `BOARD_SPI2_MISO_PIN`: 33
- `BOARD_SPI2_SCK_PIN`: 32
- `BOARD_SPI3_NSS_PIN`: 41
- `BOARD_SPI3_MOSI_PIN`: 4
- `BOARD_SPI3_MISO_PIN`: 43
- `BOARD_SPI3_SCK_PIN`: 42
- `BOARD_JTMS_SWDIO_PIN`: 39
- `BOARD_JTCK_SWCLK_PIN`: 40
- `BOARD_JTDI_PIN`: 41
- `BOARD_JTDO_PIN`: 42
- `BOARD_NJTRST_PIN`: 43

## Hardware Design Files

The hardware schematics and board layout files are available in the Maple Github repository. Other than the processor used, the design files for the Maple RET6 edition are identical to the Maple Rev 5, which are in the `maple-r5` subdirectory of the Maple repository. A schematic for a JTAG adapter suitable for use with Maple is available in the `jtagadapter` directory.

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/maple.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 5V 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 5V-tolerant.

## Errata

This section lists known issues and warnings for the Maple RET6 Edition.

- Power Supply Marketing Mistake: We originally sold the Maple RET6 Edition advertising that it was capable of supplying up to 800 mA; the correct value is 500 mA.

- UART4, UART5 GPIOs unavailable: Pins related to UARTs 4 and 5 are not broken out to headers (specifically, PC11/UART4_RX and PC12/UART5_TX). The RET6 Edition’s hardware layout is identical to that of the Maple Rev 5, which wasn’t designed for use with these STM32F103RET6-only peripherals.
- DAC channel 2 on BOARD_LED_PIN: The Maple Rev 5 connects PA5 to the board’s built-in LED; this is the same GPIO bit which is connected to the DAC’s channel 2 output. This is also due to the RET6 Edition’s board layout being copied from the base Maple Rev 5.

- Reset and PB4 tied together: The Maple’s reset line is also connected to PB4, which is labeled on the silkscreen as pin 43. Thus, attempting to use pin 43 as a GPIO may reset your board. This has other implications. Since PB4 is also the JTAG NJTRST line, this prevents the JTAG “reset halt” command from working properly. Also, since PB4 is SPI3_MISO, the SPI3 peripheral is not fully usable.

## Recommended Reading

- STMicro documentation for STM32F103RE microcontroller:

  > - Datasheet (PDF)
  > - Reference Manual (PDF)
  > - Programming Manual (PDF; assembly language and register reference)
  > - ST’s STM32F103RE reference page

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