https://github.com/leaflabs/maple/blob/master/maple‑r5/maple‑r5‑schematic.pdf 

Contents: [Dobrica Pavlinušić's random unstructured stuff]
• Dobrica Pavlinušić's random unstructured stuff (specification) 
• Dobrica Pavlinušić's random unstructured stuff (serial flash) 
• Dobrica Pavlinušić's random unstructured stuff (maple boot loader) 
• Dobrica Pavlinušić's random unstructured stuff (STM32 Arduino upgrade) 
• Dobrica Pavlinušić's random unstructured stuff (bootloader) 
• Dobrica Pavlinušić's random unstructured stuff (build) 

specification
STM32 F103RB: a 32‑bit ARM Cortex M3 microprocessor
 Clock Speed: 72 MHz
 Operating Voltage: 3.3V
 Input Voltage (recommended): 3.0V‑12V
 39 Digital I/O Pins (GPIO)
 16 Analog Input Pins
 12‑bit ADC resolution (ADC)
 15 PWM pins at 16‑bit resolution (PWM)
 Dedicated USB port for programming and communications (USB)
 External JTAG interface (USB)
 128 Flash and 20KB SRAM
 64 Channel nested vector interrupt handler (including external interrupt on GPIO’s)
 Integrated SPI (SPI)
 Integrated I2C (I2C)
 7 Channels of Direct Memory Access (DMA)
 3 USART devices
 Four 4‑channel Timers (Timers)
 Supplies up to 500mA @ 3.3v
 Support for low power and sleep modes (<500uA)
serial flash
Press boot 0, press reset, release reset, release boot 0
dpavlin@nuc:/nuc/stm32$ git clone https://github.com/jsnyder/stm32loader

dpavlin@nuc:/nuc/stm32/stm32loader$ ./stm32loader.py -p /dev/ttyUSB0 
Bootloader version 22
Chip id: 0x410 (STM32 Medium-density)

dpavlin@nuc:/nuc/stm32/stm32loader$ ./stm32loader.py -p /dev/ttyUSB0 -e -w -v maple_rev5_boot20.bin
Bootloader version 22
Chip id: 0x410 (STM32 Medium-density)
Write 256 bytes at 0x8000000
Write 256 bytes at 0x8000100
...

maple boot loader
dpavlin@nuc:/nuc/stm32/stm32loader$ wget http://docs.leaflabs.com/static.leaflabs.com/pub/leaflabs/maple-bootloader/maple_boot.bin

dpavlin@nuc:/nuc/stm32/stm32loader$ ./stm32loader.py -p /dev/ttyUSB0 -e -w -v maple_boot.bin

STM32 Arduino upgrade
bootloader
• https://github.com/rogerclarkmelbourne/STM32duino‑bootloader 

dpavlin@nuc:/nuc/stm32/stm32loader$ wget https://github.com/rogerclarkmelbourne/STM32duino-bootloader/raw/master/STM32F1/binaries/maple_rev5_boot20.bin

maple r5 is not reported with dfu‑util
https://github.com/rogerclarkmelbourne/STM32duino‑bootloader/pull/20 
build
dpavlin@nuc:/nuc/stm32/STM32duino-bootloader$ make maple-rev5

...

Copying to binaries folder

cp build/maple_boot.bin bootloader_only_binaries/maple_rev5_boot20.bin