5 KL27Z is configured to use internal 48MHz RC oscillator.
7 The board has push button on PTA4 and LED on PTD7. The button works as 'a' key and the LED as an indicator for capslock.
12 This board acommodates 48QFN chip.
15 - pcb layout https://deskthority.net/resources/image/33293
16 - schematic https://deskthority.net/resources/image/33252
19 39 ..... 44 \ conn / 1 ..... 6
24 31 .........24 23............ 14
26 1 PTD6 12 PTC3 23 GND 34 PTE20*
27 2 PTD5 13 PTC2 24 PTA18 35 PTA20 Reset
28 3 PTD4 14 PTC1 25 3.3V 36 PTA3 SWD_DIO
29 4 PTD3* 15 PTC0* 26 PTA4 NMI 37 PTA0 SWD_CLK
30 5 PTD2* 16 PTB17* 27 PTA2 38 3.3V
31 6 PTD1* 17 PTB16* 28 PTA1 39 GND
32 7 PTD0* 18 PTB3* 29 PTE25* 40 VBUS VREGIN
33 8 PTC7 19 PTB2* 30 PTE24* 41 USB D-
34 9 PTC6 20 PTB1 31 PTE30 42 USB D+
35 10 PTC5 21 PTB0 32 PTE29* 43 GND
36 11 PTC4 22 PTA19 33 PTE21* 44 USB Shield
41 This board acommodates 48QFN chip.
62 9 PTA0 SWD_CLK 20 PTC2
65 12 PTA3 SWD_DIO 17 PTB0
66 13 PTA4 NMI 16 PTA20 Reset
70 #### Pinouts difference between 32QFN and 48QFN
71 48QFN doesn't have PTE0
72 32QFN doesn't have PTD0-3, PTC0, PTE20-21,24,25,29, PTB2-3,16,17
74 ### ROM bootloader pins
75 See Reference Manual Chapter 13.
86 Due to errata e9457, need to pull-up `SPI0_SS_b`(or `SPI0_SCK`) to prevent false detection of SPI.
87 The errata doesn't refer UART though, `LPUART0_RX` also requires pull-up or down resisitor from experience.
88 Without resistor it easily false-detects activity on UART interface with finger touch on the pin.
95 ### Deskthority thread
96 https://deskthority.net/workshop-f7/can-we-design-the-teensy-alternative-for-keyboards-t13662-510.html
99 http://www.nxp.com/products/microcontrollers-and-processors/arm-processors/kinetis-cortex-m-mcus/l-series-ultra-low-power-m0-plus/kinetis-kl2x-48-mhz-usb-ultra-low-power-microcontrollers-based-on-arm-cortex-m0-plus:KL2x
101 ### KL27Z128/256 Data Sheet
102 http://www.nxp.com/assets/documents/data/en/data-sheets/KL27P64M48SF6.pdf
104 ### KL27Z128/256 Reference Manual
105 http://www.nxp.com/assets/documents/data/en/reference-manuals/KL27P64M48SF6RM.pdf
108 http://www.nxp.com/assets/documents/data/en/errata/KINETIS_L_1N71K.pdf
111 e9457: Kinetis Flashloader/ ROM Bootloader: The peripheral auto-detect code in
112 bootloader can falsely detect presence of SPI host causing non-responsive
114 Description: During the active peripheral detection process, the bootloader can interpret spurious data on
115 the SPI peripheral as valid data. The spurious data causes the bootloader to shutdown all
116 peripherals except the “falsely detected" SPI and enter the command phase loop using the
117 SPI. After the bootloader enters the command phase loop using the SPI, the other peripherals
118 are ignored, so the desired peripheral is no longer active.
119 The bootloader will not falsely detect activity on the I2C, UART, or USB interfaces, so only the
120 SPI interface is affected.
121 Workaround: Ensure that there is an external pull-up on the SPI chip-select pin or that the pin is driven high.
122 This will prevent the bootloader from seeing spurious data due to activity on the SPI clock pin.
124 ### Kinetis Bootloader and blhost
125 http://www.nxp.com/products/microcontrollers-and-processors/arm-processors/kinetis-cortex-m-mcus/kinetis-symbols-footprints-and-models/kinetis-bootloader:KBOOT
136 Flash firmware with ROM bootloader.
138 blhost -u -- flash-image build/kl27z.hex erase
143 - Fix boards/ELF files
144 - add macro `USBx_CTL_RESUME` to ChibiOS-Contrib/os/common/ext/CMSIS/KINETIS/kl27zxxx.h