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Maple RET6 Edition

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.

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© Copyright 2010, LeafLabs, LLC. Last updated on May 23, 2011. Created using Sphinx 1.0.6.