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.
The Maple RET6 Edition is powered in the same way as the standard Maple.
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 12V, and potentially even lower depending upon the current draw requirements of the application. The same goes for powering off LiPo batteries.
Please see Power Regulation on the Maple for more information.
Power regulation on the Maple RET6 works in the same way as the standard Maple.
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 light up.
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.
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).
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.
Note that this table is not exhaustive; on some pins, more peripherals are available than are listed here.
The following table shows what pins are associated with each GPIO port.
|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|
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|
The following table shows which pins connect to which EXTI lines on the Maple RET6 Edition.
|EXTI0||D2, D15, D27|
|EXTI1||D3, D16, D28|
|EXTI2||D1, D17, D25|
|EXTI3||D0, D18, D42|
|EXTI5||D4, D13, D20|
|EXTI6||D5, D12, D35|
|EXTI7||D9, D11, D36|
|EXTI8||D6, D14, D37|
|EXTI9||D7, D24, D38|
|EXTI10||D8, D26, D29|
|EXTI13||D21, D32, D39|
|EXTI14||D22, D33, D40|
|EXTI15||D23, D34, D41|
The Maple RET6 Edition has three serial ports whose pins are broken out to headers (also known as USARTs). They communicate using the pins given in the following table.
Unfortunately, UART4 and UART5 aren’t completely available.
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.
This section lists the Maple RET6 Edition’s board-specific values.
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
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.
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.
STMicro documentation for STM32F103RE microcontroller: