Maple RET6 Edition¶
This page is a general resource for information specific to the Maple RET6 Edition. The Maple RET6 Edition is a “beta” board released as a simple way to get a more powerful chip (the STM32F103RET6, hence the name) than the one on the base Maple (the STM32F103RBT6) in the hands of Maple developers.
Contents
Technical Specifications¶
- MCU: STM32F103RET6, a 32-bit ARM Cortex M3 microprocessor
- Clock Speed: 72 MHz
- 512 KB Flash and 64 KB SRAM
- 43 Digital I/O Pins (GPIO)
- 18 PWM pins at 16 bit resolution (PWM)
- 15 analog input pins, 12 bit ADC resolution (ADC)
- Built-in, 2 channel DAC at 12 bit resolution (dac.h).
- 2 SPI peripherals with I2S support (SPI)
- 2 I2C peripherals (I2C)
- 12 Channels of Direct Memory Access (DMA) (dma.h) with 2 DMA controllers
- 3 USART devices (USART)
- 2 advanced, 4 general-purpose, and 2 basic timers (Timers)
- Dedicated USB port for programming and communications (USB)
- JTAG (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
- Four layer design
- Support for low power, sleep, and standby modes (<500 μA)
- Operating Voltage: 3.3 V
- Input Voltage (recommended): 4 V — 12 V
- Dimensions are 2.05″ × 2.1″
Powering the Maple RET6 Edition¶
The Maple RET6 Edition is powered in the same way as the standard Maple.
Warning
The RET6 Edition silkscreen falsely indicates that the barrel jack accepts up to 18 V. We recommend a barrel jack input voltage no greater than 12 V.
See this erratum for more information.
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 on the back of the RET6 Edition’s silkscreen) 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 a summary of the available functionality on every GPIO pin, by peripheral type. The “5 V?” column documents whether or not the pin is 5 volt tolerant.
| Pin | GPIO | ADC | Timer | I2C | UART/USART | SPI | 5 V? |
|---|---|---|---|---|---|---|---|
| D0 | PA3 | CH3 | 2_CH4 | 2_RX | |||
| D1 | PA2 | CH2 | 2_CH3 | 2_TX | |||
| D2 | PA0 | CH0 | 2_CH1_ETR | 2_CTS | |||
| D3 | PA1 | CH1 | 2_CH2 | 2_RTS | |||
| D4 | PB5 | 1_SMBA | 3_MOSI | ||||
| D5 | PB6 | 4_CH1 | 1_SCL | Yes | |||
| D6 | PA8 | 1_CH1 | 1_CK | Yes | |||
| D7 | PA9 | 1_CH2 | 1_TX | Yes | |||
| D8 | PA10 | 1_CH3 | 1_RX | Yes | |||
| D9 | PB7 | 4_CH2 | 1_SDA | Yes | |||
| D10 | PA4 | CH4 | 2_CK | 1_NSS | |||
| D11 | PA7 | CH7 | 3_CH2 | 1_MOSI | |||
| D12 | PA6 | CH6 | 3_CH1 | 1_MISO | |||
| D13 | PA5 | CH5 | 1_SCK | ||||
| D14 | PB8 | 4_CH3 | Yes | ||||
| D15 | PC0 | CH10 | |||||
| D16 | PC1 | CH11 | |||||
| D17 | PC2 | CH12 | |||||
| D18 | PC3 | CH13 | |||||
| D19 | PC4 | CH14 | |||||
| D20 | PC5 | CH15 | |||||
| D21 | PC13 | ||||||
| D22 | PC14 | ||||||
| D23 | PC15 | ||||||
| D24 | PB9 | 4_CH4 | Yes | ||||
| D25 | PD2 | 3_ETR | 5_RX | Yes | |||
| D26 | PC10 | 4_TX | Yes | ||||
| D27 | PB0 | CH8 | 3_CH3 | ||||
| D28 | PB1 | CH9 | 3_CH4 | ||||
| D29 | PB10 | 2_SCL | 3_TX | Yes | |||
| D30 | PB11 | 2_SDA | 3_RX | Yes | |||
| D31 | PB12 | 1_BKIN | 2_SMBA | 3_CK | 2_NSS | Yes | |
| D32 | PB13 | 1_CH1N | 3_CTS | 2_SCK | Yes | ||
| D33 | PB14 | 1_CH2N | 3_RTS | 2_MISO | Yes | ||
| D34 | PB15 | 1_CH3N | 2_MOSI | Yes | |||
| D35 | PC6 | 8_CH1 | Yes | ||||
| D36 | PC7 | 8_CH2 | Yes | ||||
| D37 | PC8 | 8_CH3 | Yes | ||||
| D38 | PC9 | 8_CH4 | Yes | ||||
| D39 | PA13 | Yes | |||||
| D40 | PA14 | Yes | |||||
| D41 | PA15 | 3_NSS | Yes | ||||
| D42 | PB3 | 3_SCK | Yes |
GPIO Port Pin Map¶
The following table shows what pins are associated with each GPIO port.
| GPIOA | GPIOB | GPIOC |
|---|---|---|
| PA0: D2 | PB0: D27 | PC0: D15 |
| PA1: D3 | PB1: D28 | PC1: D16 |
| PA2: D1 | PB2: - | PC2: D17 |
| PA3: D0 | PB3: D42 | PC3: D18 |
| PA4: D10 | PB4: D43 | PC4: D19 |
| PA5: D13 | PB5: D4 | PC5: D20 |
| PA6: D12 | PB6: D5 | PC6: D35 |
| PA7: D11 | PB7: D9 | PC7: D36 |
| PA8: D6 | PB8: D14 | PC8: D37 |
| PA9: D7 | PB9: D24 | PC9: D38 |
| PA10: D8 | PB10: D29 | PC10: D26 |
| PA11: - | PB11: D30 | PC11: - |
| PA12: - | PB12: D31 | PC12: - |
| PA13: D39 | PB13: D32 | PC13: D21 |
| PA14: D40 | PB14: D33 | PC14: D22 |
| PA15: D41 | PB15: D34 | PC15: D23 |
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, 42 |
| 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, 39 |
| EXTI14 | 22, 33, 40 |
| EXTI15 | 23, 34, 41 |
USART Pin Map¶
The Maple RET6 Edition has three serial ports whose pins are broken out to headers (also known as USARTs). 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.
Low-Noise ADC Pins¶
The six pins at the bottom right of the board (D15—D20) generally offer lower-noise ADC performance than other pins on the board. If you’re concerned about getting good ADC readings, we recommend using one of these pins to take your measurements. More details in the Maple hardware documentation.
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 (however, pin D43 is not usable)
- BOARD_NR_PWM_PINS: 18
- boardPWMPins: 0, 1, 2, 3, 5, 6, 7, 8, 9, 11, 12, 14, 24, 27, 28, 35, 36, 37
- BOARD_NR_ADC_PINS: 15
- boardADCPins: 0, 1, 2, 3, 10, 11, 12, 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: 2 (unfortunately, due to the Maple Rev 5 design, SPI3 is unavailable).
- 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_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. Some of these are simply due to the RET6 Edition using the Maple’s circuit board, which was not designed to accomodate extra features only available on the STM32F103RET6.
Barrel jack power supply voltage mistake: The silkscreen next to the barrel jack connector incorrectly indicates that up to an 18 V input voltage is allowed. We do not recommend exceeding 12 V.
See this Maple erratum for more information.
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). This is due to the RET6 Edition’s board layout being that of the Maple Rev 5, which was not designed with these RET6-specific features in mind.
- 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 that of the Maple Rev 5. The DAC output channel is still available, and (if you use the standard libmaple DAC interface) its output is buffered by default, so this may not significantly interfere with its functionality.
- Reset and PB4 tied together: The RET6 Edition’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 can 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.
- SDIO lines not broken out: The RET6 Edition’s SDIO peripheral is not usable, as some of its data lines are either not broken out or used for other purposes. This is also due to the RET6 Edition’s board layout being that of the Maple Rev 5.
- ADC on BOARD_LED_PIN: We originally sold the Maple RET6 Edition advertising 16 analog input lines. However, one of them (the one on pin 13) is also connected to the built-in LED. The voltage drop across the LED means that the analog to digital converter on that pin is not really useful. While it is still usable, its readings will be incorrect.
Recommended Reading¶
STMicro documentation for STM32F103RE microcontroller:
- Datasheet (PDF); covers STM32F103xC, STM32F103xD, STM32F103xE.
- Reference Manual RM0008 (PDF); general, definitive resource for STM32F1 line.
- Programming Manual PM0056 (PDF); assembly language and register reference.
- STM32F103RE overview page with links to further references.
