136 lines
5.9 KiB
Markdown
136 lines
5.9 KiB
Markdown
## Hardware Information
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The YANG HHKB BLE controller design is similiar to hasu's
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controller. Most pins are compatiable.
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**MCU**: ATmega32U4
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**Bluetooth**: MDBT40 (nRF51822-based), with Adafruit Bluefruit LE UART Friend firmware.
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**Power**: 3.3V
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**CPU Frequency**: 8MHz
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**Bootloader**: Lufa MassStorage
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## Pin usage
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| Description | HASU pin usage | YANG mod changed |
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|:------------------------------------ | ---------------------- | -------------------------- |
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| ~KEY: Lo(0) when key is pressed | PD7 input(with pullup) | |
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| Hysteresis: Hi(1) if key was pressed | PB7 output | |
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| Row selector bit0 | PB0 output | |
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| Row selector bit1 | PB1 output | |
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| Row selector bit2 | PB2 output | |
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| Col selector bit0 | PB3 output | |
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| Col selector bit1 | PB4 output | |
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| Col selector bit2 | PB5 output | |
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| Key unable | PB6 output | |
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| Switch power | PD4 output | PD6 output (PMOS FET) |
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| Bluetooth UART Rx | PC4 input | PD2 |
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| Bluetooth UART Tx | PC5 output | PD3 |
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| Bluetooth power | | PD5 output (low: power on) |
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| LED 0 | | PF4 |
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| LED 2 | | PF1 |
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| LED 4 | | PF0 |
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| Unused for PRO2 | PC6 | |
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| Unused for PRO2 | PC7 | |
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| Inner USB power | | PF7 |
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## How to flash LUFA MassStorage bootloader on Linux
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The FAT filesystem on Linux very often cannot flush the write cache,
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leading to broken firmware in the flash.
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We can use `dd` to write to the virtual block storage directly to
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bypass the vfs layer.
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```
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dd if=FLASH.bin of=<path of virtual block device> seek=4
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```
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Skip 4 sectors because the default sector size of the virtual device
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and dd is 512 bytes and the emulated flash file starts at 5th sector.
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## How to find the path of the virtual block device
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After the keyboard boots into flash mode, on Linux system you should
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be able to find the block device in `dmesg` logs.
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For exmaple if you type
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```
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sudo dmesg
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```
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You should find something like
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```
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[357885.143593] usb 1-1.4: USB disconnect, device number 24
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[357885.627740] usb 1-1.4: new full-speed USB device number 25 using xhci_hcd
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[357885.729486] usb 1-1.4: New USB device found, idVendor=03eb, idProduct=1962, bcdDevice= 0.01
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[357885.729492] usb 1-1.4: New USB device strings: Mfr=0, Product=0, SerialNumber=0
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[357885.745620] SCSI subsystem initialized
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[357885.746712] usb-storage 1-1.4:1.0: USB Mass Storage device detected
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[357885.746818] scsi host0: usb-storage 1-1.4:1.0
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[357885.746919] usbcore: registered new interface driver usb-storage
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[357885.747689] usbcore: registered new interface driver uas
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[357886.766755] scsi 0:0:0:0: Direct-Access LUFA Bootloader 0.00 PQ: 0 ANSI: 0
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[357886.773216] scsi 0:0:0:0: Attached scsi generic sg0 type 0
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[357886.777474] sd 0:0:0:0: [sdx] 134 512-byte logical blocks: (68.6 kB/67.0 KiB)
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[357886.780300] sd 0:0:0:0: [sdx] Write Protect is off
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[357886.780302] sd 0:0:0:0: [sdx] Mode Sense: 00 00 00 00
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[357886.783113] sd 0:0:0:0: [sdx] Asking for cache data failed
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[357886.783114] sd 0:0:0:0: [sdx] Assuming drive cache: write through
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[357886.842676] sdx:
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[357886.859528] sd 0:0:0:0: [sdx] Attached SCSI removable disk
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```
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The `sdx` is the block device name and the full path is at `/dev/sdx`
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The above flash command will become
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```
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dd if=FLASH.bin of=/dev/sdx seek=4
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```
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## Adafruit Bluefruit LE UART configuraton
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The default baud rate used by the firmware is 76800 although adafruit
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do not recommend using higher baudrates than 9600 because the nRF51
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UART can drop characters.
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Double speed mode to get more accurate async reading because the F_CPU
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speed is 8MHz.
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## Power saving mode design
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Power saving is only enabled when USB is detached and using battery
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power. Here we define several levels of power saving mode, each saves
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more power but takes longer to resume operation.
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1. Level 1: idle mode is activated after a short configurable time
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(MATRIX_POWER_SAVE_TIMEOUT_MS) MCU is put into sleep mode and only
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scan the matrix per 15ms. PORTB pins are set to input with pull-up
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to save power. Sensing PCB is powered down between scans.
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2. Level 2: after idling for longer (MATRIX_POWER_SAVE_TIMEOUT_L2_MS)
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we entry this state. Matrix scan is skipped until the time lapses
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900ms.
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2. Level 3: sleep mode is activated after a longer timeout
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(MATRIX_POWER_SAVE_TIMEOUT_L3_MS) Bluetooth module is powered down.
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## Battery reading
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VBAT is connected to AIN6 pin on the MDBT40 module and the AREF pin is
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the reference voltage. Doing a ADC with AT+HWDAC=6 will return the
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difference between VBAT and VREF.
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It seems when fully charged the ADC read is 550. Likely VREF is 3311mV
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and the fully charged VBAT is thus 3861mV.
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Enable battery service with AT+BLEBATTEN=1 first then we can update the
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battery level by using AT+BLEBATTVAL=%d
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## References
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* https://github.com/joric/qmk/wiki/hhkb_ble
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* https://github.com/tomsmalley/custom-topre-guide
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* https://github.com/abcminiuser/lufa/blob/master/Bootloaders/MassStorage/Lib/VirtualFAT.h
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