feat(split): wired split over serial support (WIP 2023-12-18)

app/src/split/CMakeLists.txt

@@ -3,4 +3,8 @@
 
 if (CONFIG_ZMK_SPLIT_BLE)
     add_subdirectory(bluetooth)
-endif()
+endif()
+
+if (CONFIG_ZMK_SPLIT_SERIAL)
+    add_subdirectory(serial)
+endif()

app/src/split/Kconfig

@@ -18,6 +18,10 @@ config ZMK_SPLIT_BLE
     select BT_USER_PHY_UPDATE
     select BT_AUTO_PHY_UPDATE
 
+config ZMK_SPLIT_SERIAL
+    bool "Serial"
+    select RING_BUFFER
+
 endchoice
 
 config ZMK_SPLIT_PERIPHERAL_HID_INDICATORS
@@ -30,3 +34,4 @@ config ZMK_SPLIT_PERIPHERAL_HID_INDICATORS
 endif
 
 rsource "bluetooth/Kconfig"
+rsource "serial/Kconfig"

app/src/split/serial/CMakeLists.txt

@@ -0,0 +1,6 @@
+# Copyright (c) 2023 The ZMK Contributors
+# SPDX-License-Identifier: MIT
+
+if (CONFIG_ZMK_SPLIT_ROLE_CENTRAL)
+  target_sources(app PRIVATE central.c)
+endif()

app/src/split/serial/Kconfig

@@ -0,0 +1,23 @@
+if ZMK_SPLIT && ZMK_SPLIT_SERIAL
+
+menu "Serial Transport"
+
+config ZMK_SPLIT_SERIAL_UART
+    bool "Serial over UART"
+    default ZMK_SPLIT_SERIAL
+
+config ZMK_SPLIT_SERIAL_CDC_ACM
+    bool "Serial over USB CDC ACM"
+    default n
+
+config ZMK_SPLIT_SERIAL_BITMAP
+    bool "Serial bitmap protocol"
+    default ZMK_SPLIT_SERIAL
+
+config ZMK_SPLIT_SERIAL_CONVERTER
+    bool "Serial bitmap protocol"
+    default n
+
+endmenu
+
+endif

app/src/split/serial/central.c

@@ -0,0 +1,210 @@
+#include <zephyr/device.h>
+#include <zephyr/drivers/uart.h>
+#include <zephyr/kernel.h>
+#include <zephyr/logging/log.h>
+#include <zephyr/sys/crc.h>
+#include <zephyr/sys/ring_buffer.h>
+
+#include <zephyr/sys/byteorder.h>
+#include <zephyr/bluetooth/bluetooth.h>
+
+#include <zmk/events/position_state_changed.h>
+
+// TODO TODO TODO
+LOG_MODULE_REGISTER(slicemk);
+
+// TODO TODO TODO kconfig? is there an existing one to use? allow different rx
+// and tx sizes?
+
+#define SERIAL_MSG_PREFIX "UarT"
+
+// The serial protocol is defined for payloads of up to 127 bytes. 256 should be
+// enough to ensure that bytes are not lost. TODO TODO TODO 254, make size 400
+#define SERIAL_BUF_SIZE 256
+
+struct serial_device {
+    const struct device *dev;
+    uint8_t rx_buf[SERIAL_BUF_SIZE], tx_buf[SERIAL_BUF_SIZE];
+    struct ring_buf rx_rb, tx_rb;
+};
+
+static struct serial_device serial_devs[] = {
+#ifdef CONFIG_ZMK_SPLIT_SERIAL_UART
+    {.dev = DEVICE_DT_GET(DT_CHOSEN(zmk_split_uart))},
+#endif
+#ifdef CONFIG_ZMK_SPLIT_SERIAL_CDC_ACM
+    {.dev = DEVICE_DT_GET(DT_CHOSEN(zmk_split_cdc_acm))},
+#endif
+};
+
+#define CONFIG_ZMK_SPLIT_SERIAL_COUNT ARRAY_SIZE(serial_devs)
+
+#define POSITION_STATE_DATA_LEN 16
+static uint8_t position_state[POSITION_STATE_DATA_LEN];
+static uint8_t changed_positions[POSITION_STATE_DATA_LEN];
+
+K_MSGQ_DEFINE(peripheral_event_msgq, sizeof(struct zmk_position_state_changed), 10, 4);
+
+void peripheral_event_work_callback(struct k_work *work) {
+    struct zmk_position_state_changed ev;
+    while (k_msgq_get(&peripheral_event_msgq, &ev, K_NO_WAIT) == 0) {
+        LOG_DBG("Trigger key position state change for %d", ev.position);
+        ZMK_EVENT_RAISE(new_zmk_position_state_changed(ev));
+    }
+}
+
+// TODO TODO TODO this was copied from split bt. can go into
+// app/src/split/split.c
+K_WORK_DEFINE(peripheral_event_work, peripheral_event_work_callback);
+
+static void serial_handle_bitmap(uint8_t *data, uint8_t len) {
+    for (int i = 0; i < POSITION_STATE_DATA_LEN; i++) {
+        changed_positions[i] = ((uint8_t *)data)[i] ^ position_state[i];
+        position_state[i] = ((uint8_t *)data)[i];
+        LOG_DBG("TODO TODO TODO data: %d", position_state[i]);
+    }
+
+    for (int i = 0; i < POSITION_STATE_DATA_LEN; i++) {
+        for (int j = 0; j < 8; j++) {
+            if (changed_positions[i] & BIT(j)) {
+                uint32_t position = (i * 8) + j;
+                bool pressed = position_state[i] & BIT(j);
+
+                // TODO TODO TODO does zero make sense? check ble central. what
+                // slot is central itself?
+                int slot = 0;
+
+                struct zmk_position_state_changed ev = {.source = slot,
+                                                        .position = position,
+                                                        .state = pressed,
+                                                        .timestamp = k_uptime_get()};
+
+                k_msgq_put(&peripheral_event_msgq, &ev, K_NO_WAIT);
+                k_work_submit(&peripheral_event_work);
+            }
+        }
+    }
+}
+
+static void serial_handle(uint32_t cmd, uint8_t *data, uint8_t len) {
+    switch (cmd) {
+    // Handle bitmap split transformed (bst) version 0.
+    case 0x62737400:
+        serial_handle_bitmap(data, len);
+        break;
+
+    default:
+        LOG_ERR("Received unexpected UART command 0x%08x", cmd);
+        break;
+    }
+}
+
+static void serial_callback_rx(const struct device *dev, struct serial_device *ud) {
+    uint8_t c;
+    while (uart_fifo_read(dev, &c, 1) == 1) {
+        ring_buf_put(&ud->rx_rb, &c, 1);
+    }
+
+    // Continue processing data as long as the buffer exceeds the header length
+    // (13 bytes).
+    uint8_t data[SERIAL_BUF_SIZE];
+    while (ring_buf_peek(&ud->rx_rb, data, 13) == 13) {
+        // Discard single byte if prefix does not match.
+        if (memcmp(data, SERIAL_MSG_PREFIX, strlen(SERIAL_MSG_PREFIX))) {
+            uint8_t discard;
+            ring_buf_get(&ud->rx_rb, &discard, 1);
+            continue;
+        }
+
+        // Stop processing if message body is not completely buffered.
+        int len = data[12];
+        int total = len + 13;
+        if (ring_buf_size_get(&ud->rx_rb) < total) {
+            return;
+        }
+
+        // Check message checksum and handle message.
+        uint32_t cmd, crc;
+        ring_buf_get(&ud->rx_rb, data, total);
+        memcpy(&cmd, &data[4], sizeof(cmd));
+        memcpy(&crc, &data[8], sizeof(crc));
+        if (crc == crc32_ieee(&data[13], len)) {
+            serial_handle(cmd, &data[13], len);
+        } else {
+            LOG_ERR("received UART message with invalid CRC32 checksum");
+        }
+    }
+}
+
+static bool serial_callback_tx(const struct device *dev, struct serial_device *ud) {
+    // Read data from buffer. Stop transmitting if buffer is empty.
+    uint8_t data[32];
+    int len = ring_buf_peek(&ud->tx_rb, data, sizeof(data));
+    if (len == 0) {
+        return true;
+    }
+
+    // Write data to UART and remove number of bytes written from buffer.
+    int ret = uart_fifo_fill(dev, data, len);
+    if (ret < 0) {
+        LOG_ERR("failed to fill UART FIFO (err %d)", ret);
+        return true;
+    }
+    ring_buf_get(&ud->tx_rb, data, ret);
+    return false;
+}
+
+static void serial_callback(const struct device *dev, void *data) {
+    struct serial_device *sd = data;
+
+    // TODO TODO TODO lookup index in serial_devs array for slot ID?
+    if (uart_irq_update(sd->dev)) {
+        if (uart_irq_rx_ready(sd->dev)) {
+            serial_callback_rx(dev, sd);
+        }
+
+        if (uart_irq_tx_ready(sd->dev)) {
+            // If transmission complete, disable IRQ until next transmission.
+            bool complete = serial_callback_tx(dev, sd);
+            if (complete) {
+                uart_irq_tx_disable(sd->dev);
+            }
+        }
+    }
+}
+
+void serial_write(struct serial_device *sb, uint32_t cmd, uint8_t *data, uint8_t len) {
+    // TODO TODO TODO use buf with size SERIAL_BUF_SIZE. do single
+    // ring_buf_put() to avoid potential race
+    uint8_t header[13] = SERIAL_MSG_PREFIX;
+    memcpy(&header[4], &cmd, sizeof(cmd));
+    uint32_t crc = crc32_ieee(data, len);
+    memcpy(&header[8], &crc, sizeof(crc));
+    header[12] = len;
+    ring_buf_put(&sb->tx_rb, header, sizeof(header));
+    ring_buf_put(&sb->tx_rb, data, len);
+    uart_irq_tx_enable(sb->dev);
+}
+
+static int serial_init() {
+    for (int i = 0; i < CONFIG_ZMK_SPLIT_SERIAL_COUNT; i++) {
+        struct serial_device *sd = &serial_devs[i];
+        if (!device_is_ready(sd->dev)) {
+            LOG_ERR("failed to get serial device %s", sd->dev->name);
+            return 1;
+        }
+
+        // Initialize ring buffer.
+        ring_buf_init(&sd->rx_rb, sizeof(sd->rx_buf), sd->rx_buf);
+        ring_buf_init(&sd->tx_rb, sizeof(sd->tx_buf), sd->tx_buf);
+
+        // Enable RX callback. TODO TODO TODO polling for pio. also will need
+        // tx. take code from pmk native_sim.
+        uart_irq_callback_user_data_set(sd->dev, serial_callback, sd);
+        uart_irq_rx_enable(sd->dev);
+    }
+
+    return 0;
+}
+
+SYS_INIT(serial_init, APPLICATION, 0);