This page is a general resource for information specific to the Maple.
Identifying your Rev¶We went through three versions (“Revs”) of the Maple hardware: Rev 1, Rev 3, and Rev 5 [1]; Rev 5, the final design, is currently on sale. The following sections will help you to help you identify your Rev.
Rev 5¶These boards went on sale in November 2010. They have white buttons and “r5” in small print near the “LeafLabs Maple” text next to the “infinity leaf” logo. The Maple Rev 5 repositioned the double header on the right hand side to better fit 0.1 inch pitch breadboard. This necessitated the removal of pins 21 and 22 from the double header; they are still available, but don’t have any headers installed on them.
Rev 3¶This batch of boards went on sale beginning in May 2010. They have a darker red silkscreen and the “infinity leaf” logo. The Maple Rev 3 was the first version which includes the built-in button, labeled BUT.
Rev 1¶A small number of Maple Rev 1 boards went on sale in late 2009. They have a light red silkscreen and a single pixelated leaf as a logo.
Powering the Maple¶The Maple’s power source is determined by the header to the left of the “LeafLabs” label on the silkscreen. All versions of the Maple can be powered from the barrel jack connector, USB, or a LiPo battery. We ship the Maple with a jumper on the USB selector. In order to power it off of an alternative source, unplug the Maple, 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. This pin feeds into both the digital and analog voltage regulators. However, don’t do this while simultaneously powering the board from another source, or you could damage it.
When powering the board from a barrel jack, double check the polarity of the barrel. The appropriate polarity is noted on the silkscreen right next to the connector.
Warning
Silkscreens on Maples up through Rev 5s manufactured in Spring 2011 falsely indicated that the barrel jack could be supplied by up to 18V. (Rev5s manufactured after Spring 2011 may still have this error on the silk, but it has been marked over.) 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¶Power regulation on the Maple is provided by two low dropout linear voltage regulators. (The part is the MCP1703 from Microchip, in the SOT-23A package. You can download the datasheet here ). One of the regulators supplies power to the digital voltage plane; the other supplies power to the analog voltage plane.
These voltage regulators nominally take an input of up to 16V. In addition, while the maximum continuous output current for the board is 250mA, if you are powering the board off higher voltages the amount off current it can supply goes down, due to the regulators needing to dissipate the extra power. So if you are powering the board off 12V, the max current is about 40mA at room temperature. In general (again, at room temperature) the max power dissipation (PD) for the chip is about .37W, and output current = PD/(Vin-Vout). For exact max current calculations, please refer to the datasheet linked above.
If you are planning to draw a lot of current from the Maple board, it is necessary to provide input power as close to 3.3V as possible. Powering the microcontroller circuitry and LEDs on the board alone takes approximately 30mA, so if you are powering the board with 12V that leaves only 10mA (at best) available for powering any user circuitry. Attempting to draw more than 10mA runs the risk of shorting out the power regulators and bricking your board.
Using the Built-in Battery Charger¶Maples Rev 3 and Rev 5 also have 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.
GPIO Information¶The Maple 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 Maple’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.
Note that this table is not exhaustive; on some pins, more peripherals are available than are listed here.
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.
Timer Ch. 1 Ch. 2 Ch. 3 Ch. 4 1 D6 D7 D8The following table shows which pins connect to which EXTI lines on the Maple.
EXTI Line Pins EXTI0 D2, D15, D27 EXTI1 D3, D16, D28 EXTI2 D1, D17, D25 EXTI3 D0, D18, D42 EXTI4 D10, D19 EXTI5 D4, D13, D20 EXTI6 D5, D12, D35 EXTI7 D9, D11, D36 EXTI8 D6, D14, D37 EXTI9 D7, D24, D38 EXTI10 D8, D26, D29 EXTI11 D30 EXTI12 D31 EXTI13 D21, D32, D39 EXTI14 D22, D33, D40 EXTI15 D23, D34, D41 USART Pin Map¶The Maple has three serial ports (also known as USARTs): Serial1, Serial2, and Serial3. They communicate using the pins given in the following table.
Serial Port TX RX CK CTS RTS Serial1 D7 D8 D6 Serial2 D1 D0 D10 D2 D3 Serial3 D29 D30 D31 D32 D33 Low-Noise ADC Pins¶The six pins at the bottom right of the board (D15âD20) generally offer lower-noise ADC performance than other pins on the board. If youâre concerned about getting good ADC readings, we recommend using one of these pins to take your measurements.
Maple has an electrically isolated analog power plane with its own regulator, and a geometrically isolated ground plane. Pins D15âD20 are laid out to correspond with these analog planes, and our measurements indicate that they generally have the lowest noise of all the analog lines. However, analog performance may vary depending upon the activity of the other GPIOs. Consult the Maple hardware design files for more details.
Board-Specific Values¶This section lists the Maple’s board-specific values.
The hardware schematics and board layout files are available in the Maple GitHub repository. The design files for Rev 1, Rev 3, and Rev 5 are respectively in the maple-r1, maple-r3, and maple-r5 subdirectories. 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.gitFailure Modes¶
The following are known failure modes. The failure modes aren’t design errors, but are easy ways to break or damage your board permanently.
This section documents design flaws and other errors.
General¶The following subsections lists known issues and warnings for each revision of the Maple board.
Rev 5¶Bad/Sticky Buttons: a number of Rev 3 boards sold in May-June 2010 have questionable RESET and BUT buttons.
What seems to have happened is that the flux remover we used to clean the boards before shipping eroded the plastic internals, which resulted in intermittent functionality. All buttons on all shipped boards did function in testing, but some may have been unreliable in regular use.
If you have this problem, we will be happy to ship you new buttons if you think you can re-solder them yourself, or you can ship us your board and we will swap out that part.
For reference, the button part number is KMR211GLFS and the flux remover we used is “Precision Electronics Cleaner” from RadioShack, which is “Safe on most plastics” and contains: dipropylene glycol monomethyl ether, hydrotreated heavy naphtha, dipropylene glycol methyl ether acetate (say that three times fast!), and carbon dioxide.
Resistors on pins 0 and 1: these header pins, which are RX/TX on USART2 (Serial2), have resistors in-line between the STM32 and the headers. These resistors increase the impedance of the lines for ADC reads and affect the open drain GPIO functionality of the pins.
These resistors were accidentally copied over from older Arduino USB designs, where they appear to protect the USB-Serial converter from TTL voltage on the headers.
Silkscreen Errors: the silkscreen on the bottom indicated PWM functionality on pin 25 and listen the external header GND pin as number 38 (actually 38 is connected to the BUT button). We manually sharpied over both of these mistakes.
ADC noise: generally very high, in particular when the USB port is being used for communications (including keep-alive pings when connected to a computer).
This issue was resolved in Rev 3 with a 4-layer design and a geometrically isolated ADC Vref plane.
Resistors on pins 0 and 1: these header pins, which are RX/TX on USART2 (Serial2), have resistors in-line between the STM32 and the headers. These resistors increase the impedance of the lines for ADC reads and affect the open drain GPIO functionality of the pins.
These resistors were accidentally copied over from older Arduino USB designs, where they appear to protect the USB-Serial converter from TTL voltage on the headers.
Silkscreen Differences: the pin numbering scheme on Rev 1 is different from Rev 3, and thus Rev 3 software is difficult to use with Rev 1 boards. Notably, the analog input bank is labeled A0-A4 on Rev 1 but 15-20 on Rev 3, and the extra header bank does not have a pinout table on the bottom.
No BUT Button: the BUT button, useful for serial bootloading, was only added in Rev 3. As a workaround, you can directly short the appropriate MCU pin to Vcc; see this forum posting.
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