Mitosis 是一款使用 QMK 作爲韌體所開發的無線分離式鍵盤,它不僅僅是與電腦之間無線,它的左右兩部分之間也沒有實體連線,可謂是「真 • 無線」。就我所知,有許多基於 QMK 的無線分離式鍵盤都是受到 Mitosis 的啓發。
本文將會概略性地介紹 Mitosis 是如何做到無線的。
硬體與基本架構
首先,Mitosis 是擁有並需要自製的專用接收器,而 QMK 實際上只在此接收器上運作。
Mitosis 的架構中,主要擁有這些硬體:
- 1 個 Pro Micro(ATmega32U4)。接收器的一部分,QMK 實際上只在 Pro Micro 上運作,以 USB 線連接電腦。
- 3 個 nRF51822。這是一個整合了 BLE(Bluetooth Low Energy,藍牙低功耗)等無線功能的 SoC(System On Chip)。
- 第 1 個 nRF51822 作爲接收器的一部分,負責接收來自左右兩部分鍵盤的訊號,並將其透過 UART 傳給 Pro Micro。
- 第 2、3 個 nRF51822 分別在左右兩鍵盤上,負責讀取鍵盤上的按鍵狀態,並將其透過 Gazell 傳給接收器的 nRF51822。
1 PC
2 |
3 <USB>
4 |
5 Pro Micro(QMK)
6 |
7 <UART>
8 |
9 nRF51822(#1)
10 / \
11 <Gazell> <Gazell>
12 / \
13 nRF51822(#2) nRF51822(#3)
14 | |
15 Left Keyboard Right Keyboard
可以看出,Mitosis 的架構其實很簡單。雖然這樣的架構要用上更多的 IC,以導致它感覺起來不夠精簡,但這也其容易達成、理解或修改。
總的來說,左右鍵盤上的 nRF51822 會處理各自的按鍵狀態,並各自將其透過 Gazell 傳輸給接收器上的 nRF51822,接收器受到新的按鍵狀態後,會將左右部分的按鍵狀態組合在一起,並透過 UART 傳給 Pro Micro,Pro Micro 收到來自 UART 的封包後就解析按鍵狀態,並交由 QMK 處理。
程式
從基本架構可以得知,Mitosis 總共有 4 個 MCU(1 個 Pro Micro 的 ATmega32U4,3 個 nRF51822),而它們執行的程式當然也不一樣,以下就一一介紹不同部分的程式。
左右手鍵盤(nRF51822)
首先,這部分的程式在:reversebias/mitosis/mitosis-keyboard-basic/。主要有:
main.c
是主程式。config/mitosis.h
是包含了腳位設定的標頭檔。
左右手鍵盤上 nRF51822 的程式是同一個,僅透過 #define COMPILE_RIGHT
或 #define COMPILE_LEFT
來切換不同的腳位設定和通道編號(Pipe number)而已。
在這裡有幾個重要的函數(僅列出函數名稱):
read_keys()
send_data()
handler_maintenance()
handler_debounce()
handler_debounce()
先看到 handler_debounce()
這個函數,它負責處理按鍵防彈跳(Debounce)。內容如下:
1// 1000Hz debounce sampling
2static void handler_debounce(nrf_drv_rtc_int_type_t int_type)
3{
4 // debouncing, waits until there have been no transitions in 5ms (assuming five 1ms ticks)
5 if (debouncing)
6 {
7 // if debouncing, check if current keystates equal to the snapshot
8 if (keys_snapshot == read_keys())
9 {
10 // DEBOUNCE ticks of stable sampling needed before sending data
11 debounce_ticks++;
12 if (debounce_ticks == DEBOUNCE)
13 {
14 keys = keys_snapshot;
15 send_data();
16 }
17 }
18 else
19 {
20 // if keys change, start period again
21 debouncing = false;
22 }
23 }
24 else
25 {
26 // if the keystate is different from the last data
27 // sent to the receiver, start debouncing
28 if (keys != read_keys())
29 {
30 keys_snapshot = read_keys();
31 debouncing = true;
32 debounce_ticks = 0;
33 }
34 }
35
36 // looking for 500 ticks of no keys pressed, to go back to deep sleep
37 if (read_keys() == 0)
38 {
39 activity_ticks++;
40 if (activity_ticks > ACTIVITY)
41 {
42 nrf_drv_rtc_disable(&rtc_maint);
43 nrf_drv_rtc_disable(&rtc_deb);
44 }
45 }
46 else
47 {
48 activity_ticks = 0;
49 }
50}
handler_debounce()
每秒會觸發 1000 次(也就是以 1000 Hz運作,由 RTC1
處理)。
它會先判斷目前是否在防彈跳中(if (debouncing)
),如果沒有的話會去判斷目前的按鍵狀態是否和最後一次一樣,如果不一樣代表有按鍵按下或放開了,透過 read_keys()
讀取目前的按鍵狀態,並儲存爲快照 keys_snapshot
,同時開始防彈跳(將 deboducing
設爲 true
)。
一旦開始防彈跳,它就會一直確認快照與目前的按鍵狀態是否一樣,一旦不一樣就停止防彈跳,若累計達到設定的防彈跳次數就會承認快照的按鍵狀態,並將快照的值給目前的鍵值 keys
,並呼叫 send_data()
開始傳送。
handler_maintenance()
1// 8Hz held key maintenance, keeping the reciever keystates valid
2static void handler_maintenance(nrf_drv_rtc_int_type_t int_type)
3{
4 send_data();
5}
此函數的功能顯而易見,就是以 8 Hz 的頻率次數呼叫 send_data()
傳送資料。此函數由 RTC0 處理。
send_data()
1// Assemble packet and send to receiver
2static void send_data(void)
3{
4 data_payload[0] = ((keys & 1<<S01) ? 1:0) << 7 | \
5 ((keys & 1<<S02) ? 1:0) << 6 | \
6 ((keys & 1<<S03) ? 1:0) << 5 | \
7 ((keys & 1<<S04) ? 1:0) << 4 | \
8 ((keys & 1<<S05) ? 1:0) << 3 | \
9 ((keys & 1<<S06) ? 1:0) << 2 | \
10 ((keys & 1<<S07) ? 1:0) << 1 | \
11 ((keys & 1<<S08) ? 1:0) << 0;
12
13 data_payload[1] = ((keys & 1<<S09) ? 1:0) << 7 | \
14 ((keys & 1<<S10) ? 1:0) << 6 | \
15 ((keys & 1<<S11) ? 1:0) << 5 | \
16 ((keys & 1<<S12) ? 1:0) << 4 | \
17 ((keys & 1<<S13) ? 1:0) << 3 | \
18 ((keys & 1<<S14) ? 1:0) << 2 | \
19 ((keys & 1<<S15) ? 1:0) << 1 | \
20 ((keys & 1<<S16) ? 1:0) << 0;
21
22 data_payload[2] = ((keys & 1<<S17) ? 1:0) << 7 | \
23 ((keys & 1<<S18) ? 1:0) << 6 | \
24 ((keys & 1<<S19) ? 1:0) << 5 | \
25 ((keys & 1<<S20) ? 1:0) << 4 | \
26 ((keys & 1<<S21) ? 1:0) << 3 | \
27 ((keys & 1<<S22) ? 1:0) << 2 | \
28 ((keys & 1<<S23) ? 1:0) << 1 | \
29 0 << 0;
30
31 nrf_gzll_add_packet_to_tx_fifo(PIPE_NUMBER, data_payload, TX_PAYLOAD_LENGTH);
32}
此函數就是將目前的鍵值 keys
打包成資料封包並傳輸出去。keys
的值會在 handler_debounce()
中更新。
PIPE_NUMBER
的值左右鍵盤不同(在 mitosis.h
中定義),接收器藉此判斷收到的資料是來自左還是右鍵盤。
read_keys()
1// Return the key states, masked with valid key pins
2static uint32_t read_keys(void)
3{
4 return ~NRF_GPIO->IN & INPUT_MASK;
5}
此函數的功能也是很直觀,就是讀取並回傳所有的按鍵狀態。
從這裡也可以得知,Mitosis 是不用矩陣掃描(Matrix scan)的,畢竟它的按鍵數本來就比較少(左右各 23 鍵),又是分離式的鍵盤,一個 nRF51822 的 GPIO 足以分配到每個按鍵上,自然不用掃描,直接讀值就好。
接收器(nRF51822)
這部分的程式在:reversebias/mitosis/mitosis-receiver-basic/。主要有:
main.c
是主程式。
其中有幾個重要的函數(僅列出函數名稱):
nrf_gzll_host_rx_data_ready()
main()
nrf_gzll_host_rx_data_ready()
1// If a data packet was received, identify half, and throw flag
2void nrf_gzll_host_rx_data_ready(uint32_t pipe, nrf_gzll_host_rx_info_t rx_info)
3{
4 uint32_t data_payload_length = NRF_GZLL_CONST_MAX_PAYLOAD_LENGTH;
5
6 if (pipe == 0)
7 {
8 packet_received_left = true;
9 left_active = 0;
10 // Pop packet and write first byte of the payload to the GPIO port.
11 nrf_gzll_fetch_packet_from_rx_fifo(pipe, data_payload_left, &data_payload_length);
12 }
13 else if (pipe == 1)
14 {
15 packet_received_right = true;
16 right_active = 0;
17 // Pop packet and write first byte of the payload to the GPIO port.
18 nrf_gzll_fetch_packet_from_rx_fifo(pipe, data_payload_right, &data_payload_length);
19 }
20
21 // not sure if required, I guess if enough packets are missed during blocking uart
22 nrf_gzll_flush_rx_fifo(pipe);
23
24 //load ACK payload into TX queue
25 ack_payload[0] = 0x55;
26 nrf_gzll_add_packet_to_tx_fifo(pipe, ack_payload, TX_PAYLOAD_LENGTH);
27}
這是接收處理函數。當接收到資料時,以 pipe
判斷這是來自左還是右鍵盤,並設定好資料。
main()
以下省略一些不重要的程式:
1int main(void)
2{
3 /* 省略部分程式 */
4
5 // main loop
6 while (true)
7 {
8 // detecting received packet from interupt, and unpacking
9 if (packet_received_left)
10 {
11 packet_received_left = false;
12
13 data_buffer[0] = ((data_payload_left[0] & 1<<3) ? 1:0) << 0 |
14 ((data_payload_left[0] & 1<<4) ? 1:0) << 1 |
15 ((data_payload_left[0] & 1<<5) ? 1:0) << 2 |
16 ((data_payload_left[0] & 1<<6) ? 1:0) << 3 |
17 ((data_payload_left[0] & 1<<7) ? 1:0) << 4;
18
19 data_buffer[2] = ((data_payload_left[1] & 1<<6) ? 1:0) << 0 |
20 ((data_payload_left[1] & 1<<7) ? 1:0) << 1 |
21 ((data_payload_left[0] & 1<<0) ? 1:0) << 2 |
22 ((data_payload_left[0] & 1<<1) ? 1:0) << 3 |
23 ((data_payload_left[0] & 1<<2) ? 1:0) << 4;
24
25 data_buffer[4] = ((data_payload_left[1] & 1<<1) ? 1:0) << 0 |
26 ((data_payload_left[1] & 1<<2) ? 1:0) << 1 |
27 ((data_payload_left[1] & 1<<3) ? 1:0) << 2 |
28 ((data_payload_left[1] & 1<<4) ? 1:0) << 3 |
29 ((data_payload_left[1] & 1<<5) ? 1:0) << 4;
30
31 data_buffer[6] = ((data_payload_left[2] & 1<<5) ? 1:0) << 1 |
32 ((data_payload_left[2] & 1<<6) ? 1:0) << 2 |
33 ((data_payload_left[2] & 1<<7) ? 1:0) << 3 |
34 ((data_payload_left[1] & 1<<0) ? 1:0) << 4;
35
36 data_buffer[8] = ((data_payload_left[2] & 1<<1) ? 1:0) << 1 |
37 ((data_payload_left[2] & 1<<2) ? 1:0) << 2 |
38 ((data_payload_left[2] & 1<<3) ? 1:0) << 3 |
39 ((data_payload_left[2] & 1<<4) ? 1:0) << 4;
40 }
41
42 if (packet_received_right)
43 {
44 packet_received_right = false;
45
46 data_buffer[1] = ((data_payload_right[0] & 1<<7) ? 1:0) << 0 |
47 ((data_payload_right[0] & 1<<6) ? 1:0) << 1 |
48 ((data_payload_right[0] & 1<<5) ? 1:0) << 2 |
49 ((data_payload_right[0] & 1<<4) ? 1:0) << 3 |
50 ((data_payload_right[0] & 1<<3) ? 1:0) << 4;
51
52 data_buffer[3] = ((data_payload_right[0] & 1<<2) ? 1:0) << 0 |
53 ((data_payload_right[0] & 1<<1) ? 1:0) << 1 |
54 ((data_payload_right[0] & 1<<0) ? 1:0) << 2 |
55 ((data_payload_right[1] & 1<<7) ? 1:0) << 3 |
56 ((data_payload_right[1] & 1<<6) ? 1:0) << 4;
57
58 data_buffer[5] = ((data_payload_right[1] & 1<<5) ? 1:0) << 0 |
59 ((data_payload_right[1] & 1<<4) ? 1:0) << 1 |
60 ((data_payload_right[1] & 1<<3) ? 1:0) << 2 |
61 ((data_payload_right[1] & 1<<2) ? 1:0) << 3 |
62 ((data_payload_right[1] & 1<<1) ? 1:0) << 4;
63
64 data_buffer[7] = ((data_payload_right[1] & 1<<0) ? 1:0) << 0 |
65 ((data_payload_right[2] & 1<<7) ? 1:0) << 1 |
66 ((data_payload_right[2] & 1<<6) ? 1:0) << 2 |
67 ((data_payload_right[2] & 1<<5) ? 1:0) << 3;
68
69 data_buffer[9] = ((data_payload_right[2] & 1<<4) ? 1:0) << 0 |
70 ((data_payload_right[2] & 1<<3) ? 1:0) << 1 |
71 ((data_payload_right[2] & 1<<2) ? 1:0) << 2 |
72 ((data_payload_right[2] & 1<<1) ? 1:0) << 3;
73 }
74
75 // checking for a poll request from QMK
76 if (app_uart_get(&c) == NRF_SUCCESS && c == 's')
77 {
78 // sending data to QMK, and an end byte
79 nrf_drv_uart_tx(data_buffer,10);
80 app_uart_put(0xE0);
81
82 /* 省略部分程式 */
83 }
84 // allowing UART buffers to clear
85 nrf_delay_us(10);
86
87 /* 省略部分程式 */
88 }
89}
這裡就是來負責將 Gazell 接收到的左右鍵盤按鍵狀態重新打包,只要確認了來自 QMK 的輪詢請求(s
),就透過 UART 傳送出去。
傳給 QMK 的封包除了按鍵狀態外,還有一個 0xE0
作爲結束封包。
QMK / 接收器(Pro Micro)
這部分的程式在:qmk/qmk_firmware/keyboards/mitosis。主要有:
rules.mk
config.h
matrix.c
rules.mk
1# MCU name
2MCU = atmega32u4
3
4# Bootloader selection
5BOOTLOADER = caterina
6
7# Build Options
8# change yes to no to disable
9#
10BOOTMAGIC_ENABLE = no # Enable Bootmagic Lite
11MOUSEKEY_ENABLE = yes # Mouse keys
12EXTRAKEY_ENABLE = yes # Audio control and System control
13CONSOLE_ENABLE = yes # Console for debug
14COMMAND_ENABLE = yes # Commands for debug and configuration
15CUSTOM_MATRIX = yes # Remote matrix from the wireless bridge
16NKRO_ENABLE = yes # Enable N-Key Rollover
17# BACKLIGHT_ENABLE = yes # Enable keyboard backlight functionality
18UNICODE_ENABLE = yes # Unicode
19
20# # project specific files
21SRC += matrix.c serial_uart.c
這裡可以注意到作者使用了 QMK 的「Custom Matrix」功能 (CUSTOM_MATRIX = yes
及 SRC += matrix.c
),因爲 Mitosis 不像一般的鍵盤透過矩陣掃描得知按鍵狀態,而是讀取來自 nRF51822 透過 UART 傳送的封包。
config.h
config.h
主要是設定 QMK 中的各種東西,稍微熟悉 QMK 的人都不陌生。這裡僅列出重要的地方,也就是 UART 的相關設定:
1//UART settings for communication with the RF microcontroller
2#define SERIAL_UART_BAUD 1000000
3#define SERIAL_UART_RXD_PRESENT (UCSR1A & _BV(RXC1))
4#define SERIAL_UART_INIT_CUSTOM \
5 /* enable TX and RX */ \
6 UCSR1B = _BV(TXEN1) | _BV(RXEN1); \
7 /* 8-bit data */ \
8 UCSR1C = _BV(UCSZ11) | _BV(UCSZ10);
matrix.c
matrix.c
是爲了使用 QMK 的「Custom Matrix」功能所必要的檔案。
重點在 matrix_scan()
:
1uint8_t matrix_scan(void)
2{
3 uint32_t timeout = 0;
4
5 //the s character requests the RF slave to send the matrix
6 SERIAL_UART_DATA = 's';
7
8 //trust the external keystates entirely, erase the last data
9 uint8_t uart_data[11] = {0};
10
11 //there are 10 bytes corresponding to 10 columns, and an end byte
12 for (uint8_t i = 0; i < 11; i++) {
13 //wait for the serial data, timeout if it's been too long
14 //this only happened in testing with a loose wire, but does no
15 //harm to leave it in here
16 while(!SERIAL_UART_RXD_PRESENT){
17 timeout++;
18 if (timeout > 10000){
19 break;
20 }
21 }
22 uart_data[i] = SERIAL_UART_DATA;
23 }
24
25 //check for the end packet, the key state bytes use the LSBs, so 0xE0
26 //will only show up here if the correct bytes were recieved
27 if (uart_data[10] == 0xE0)
28 {
29 //shifting and transferring the keystates to the QMK matrix variable
30 for (uint8_t i = 0; i < MATRIX_ROWS; i++) {
31 matrix[i] = (uint16_t) uart_data[i*2] | (uint16_t) uart_data[i*2+1] << 5;
32 }
33 }
34
35
36 matrix_scan_quantum();
37 return 1;
38}
首先此函數會傳送一個 s
以請求 nRF51822 開始傳送按鍵狀態封包。
接著,一個 for
迴圈會處理來自 UART 的按鍵狀態封包。當接收完成後,判斷結束封包是否正確(爲 0xE0
),如果沒問題的話就將按鍵狀態封包處理並賦值給 matrix[]
,接下來就是讓 QMK 去處理了。
結語
本次簡單地介紹 Mitosis 鍵盤是如和達成無線的,但我其實沒用過 nRF51822,對 QMK 的瞭解也還很粗淺,很多細節沒辦法講解,而如果上述內容有任何錯誤也請指正。
撰寫本文時的 Mitosis 相關 repo 資訊:
- reversebias/mitosis
- nRF51822 的程式
- commit:
f2bb956f8565762212d361a42f830390ef5c6845
- qmk/qmk_firmware
- QMK 程式
- commit:
f718a10889e6adf33f3fc2f41b61cad7fe9e0c2e
文章修改記錄 2022/02/23:原本寫的各個 nRF51822 之間的通訊方式是 BLE,但應該是 Gazell,故更新內容。
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