canbus: Rework CAN command protocol

Rework the micro-controller command protocol so that it supports
direct communication with the serialqueue.c code.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

docs/CANBUS_protocol.md

@@ -0,0 +1,65 @@
+This document describes the protocol Klipper uses to communicate over
+[CAN bus](https://en.wikipedia.org/wiki/CAN_bus).
+
+# Micro-controller id assignment
+
+Klipper uses only CAN 2.0A standard size CAN bus packets, which are
+limited to 8 data bytes and an 11-bit CAN bus identifier. In order to
+support efficient communication, each micro-controller is assigned at
+run-time a unique 1-byte CAN bus nodeid (`canbus_nodeid`) for general
+Klipper command and response traffic. Klipper command messages going
+from host to micro-controller use the CAN bus id of `canbus_nodeid *
+2 + 256`, while Klipper response messages from micro-controller to
+host use `canbus_nodeid * 2 + 256 + 1`.
+
+Each micro-controller has a factory assigned unique chip identifier
+that is used during id assignment. This identifier can exceed the
+length of one CAN packet, so a hash function is used to generate a
+unique 6-byte id (`canbus_uuid`) from the factory id.
+
+# Admin messages
+
+Admin messages are used for id assignment. Admin messages sent from
+host to micro-controller use the CAN bus id `0x3f0` and messages sent
+from micro-controller to host use the CAN bus id `0x3f1`. All
+micro-controllers listen to messages on id `0x3f0`; that id can be
+thought of as a "broadcast address".
+
+## CMD_QUERY_UNASSIGNED message
+
+This command queries all micro-controllers that have not yet been
+assigned a `canbus_nodeid`. Unassigned micro-controllers will respond
+with a RESP_NEED_NODEID response message.
+
+The CMD_QUERY_UNASSIGNED message format is:
+`<1-byte message_id = 0x00>`
+
+## CMD_SET_NODEID message
+
+This command assigns a `canbus_nodeid` to the micro-controller with a
+given `canbus_uuid`.
+
+The CMD_SET_NODEID message format is:
+`<1-byte message_id = 0x01><6-byte canbus_uuid><1-byte canbus_nodeid>`
+
+## RESP_NEED_NODEID message
+
+The RESP_NEED_NODEID message format is:
+`<1-byte message_id = 0x20><6-byte canbus_uuid>`
+
+# Data Packets
+
+A micro-controller that has been assigned a nodeid via the
+CMD_SET_NODEID command can send and receive data packets.
+
+The packet data in messages using the node's receive CAN bus id
+(`canbus_nodeid * 2 + 256`) are simply appended to a buffer, and when
+a complete [mcu protocol message](Protocol.md) is found its contents
+are parsed and processed. The data is treated as a byte stream - there
+is no requirement for the start of a Klipper message block to align
+with the start of a CAN bus packet.
+
+Similarly, mcu protocol message responses are sent from
+micro-controller to host by copying the message data into one or more
+packets with the node's transmit CAN bus id (`canbus_nodeid * 2 +
+256 + 1`).

docs/Overview.md

@@ -60,6 +60,8 @@ communication with the Klipper developers.
   control API.
 - [MCU commands](MCU_Commands.md): A description of low-level commands
   implemented in the micro-controller software.
+- [CAN bus protocol](CANBUS_protocol.md): Klipper CAN bus message
+  format.
 - [Debugging](Debugging.md): Information on how to test and debug
   Klipper.
 - [Benchmarks](Benchmarks.md): Information on the Klipper benchmark

src/generic/canbus.c

@@ -82,80 +82,88 @@ console_sendf(const struct command_encoder *ce, va_list args)
 
 
 /****************************************************************
- * CAN command handling
+ * CAN "admin" command handling
  ****************************************************************/
 
-static uint8_t receive_buf[192], receive_pos;
+// Available commands and responses
-DECL_CONSTANT("RECEIVE_WINDOW", ARRAY_SIZE(receive_buf));
+#define CANBUS_CMD_QUERY_UNASSIGNED 0x00
+#define CANBUS_CMD_SET_NODEID 0x01
+#define CANBUS_RESP_NEED_NODEID 0x20
 
-static void
+// Helper to verify a UUID in a command matches this chip's UUID
-can_process_data(uint32_t id, uint32_t len, uint8_t *data)
+static int
+can_check_uuid(uint32_t id, uint32_t len, uint8_t *data)
 {
-    int rpos = receive_pos;
+    return len >= 7 && memcmp(&data[1], canbus_uuid, sizeof(canbus_uuid)) == 0;
-    if (len > sizeof(receive_buf) - rpos)
-        len = sizeof(receive_buf) - rpos;
-    memcpy(&receive_buf[rpos], data, len);
-    receive_pos = rpos + len;
 }
 
-// Helper to retry sending until successful
+// Helpers to encode/decode a CAN identifier to a 1-byte "nodeid"
-static void
+static int
-canbus_send_blocking(uint32_t id, uint32_t len, uint8_t *data)
+can_get_nodeid(void)
 {
+    if (!canbus_assigned_id)
+        return 0;
+    return (canbus_assigned_id - 0x100) >> 1;
+}
+static uint32_t
+can_decode_nodeid(int nodeid)
+{
+    return (nodeid << 1) + 0x100;
+}
+
+static void
+can_process_query_unassigned(uint32_t id, uint32_t len, uint8_t *data)
+{
+    if (canbus_assigned_id)
+        return;
+    uint8_t send[8];
+    send[0] = CANBUS_RESP_NEED_NODEID;
+    memcpy(&send[1], canbus_uuid, sizeof(canbus_uuid));
+    // Send with retry
     for (;;) {
-        int ret = canbus_send(id, len, data);
+        int ret = canbus_send(CANBUS_ID_ADMIN_RESP, 7, send);
         if (ret >= 0)
             return;
     }
 }
 
 static void
-can_process_ping(uint32_t id, uint32_t len, uint8_t *data)
+can_id_conflict(void)
 {
-    canbus_send_blocking(canbus_assigned_id + 1, 0, NULL);
+    canbus_assigned_id = 0;
+    canbus_set_filter(canbus_assigned_id);
+    shutdown("Another CAN node assigned this ID");
 }
 
 static void
-can_process_reset(uint32_t id, uint32_t len, uint8_t *data)
+can_process_set_nodeid(uint32_t id, uint32_t len, uint8_t *data)
 {
-    uint32_t reset_id = data[0] | (data[1] << 8);
+    if (len < 8)
-    if (reset_id == canbus_assigned_id)
-        canbus_reboot();
-}
-
-static void
-can_process_uuid(uint32_t id, uint32_t len, uint8_t *data)
-{
-    if (canbus_assigned_id)
         return;
-    canbus_send_blocking(CANBUS_ID_UUID_RESP, sizeof(canbus_uuid), canbus_uuid);
+    uint32_t newid = can_decode_nodeid(data[7]);
-}
+    if (can_check_uuid(id, len, data)) {
-
+        if (newid != canbus_assigned_id) {
-static void
+            canbus_assigned_id = newid;
-can_process_set_id(uint32_t id, uint32_t len, uint8_t *data)
-{
-    // compare my UUID with packet to check if this packet mine
-    if (memcmp(&data[2], canbus_uuid, sizeof(canbus_uuid)) == 0) {
-        canbus_assigned_id = data[0] | (data[1] << 8);
             canbus_set_filter(canbus_assigned_id);
         }
+    } else if (newid == canbus_assigned_id) {
+        can_id_conflict();
+    }
 }
 
+// Handle an "admin" command
 static void
 can_process(uint32_t id, uint32_t len, uint8_t *data)
 {
-    if (id == canbus_assigned_id) {
+    if (!len)
-        if (len)
+        return;
-            can_process_data(id, len, data);
+    switch (data[0]) {
-        else
+    case CANBUS_CMD_QUERY_UNASSIGNED:
-            can_process_ping(id, len, data);
+        can_process_query_unassigned(id, len, data);
-    } else if (id == CANBUS_ID_UUID) {
+        break;
-        if (len)
+    case CANBUS_CMD_SET_NODEID:
-            can_process_reset(id, len, data);
+        can_process_set_nodeid(id, len, data);
-        else
+        break;
-            can_process_uuid(id, len, data);
-    } else if (id==CANBUS_ID_SET) {
-        can_process_set_id(id, len, data);
     }
 }
 
@@ -172,6 +180,19 @@ canbus_notify_rx(void)
     sched_wake_task(&canbus_rx_wake);
 }
 
+static uint8_t receive_buf[192], receive_pos;
+DECL_CONSTANT("RECEIVE_WINDOW", ARRAY_SIZE(receive_buf));
+
+static void
+can_process_data(uint32_t id, uint32_t len, uint8_t *data)
+{
+    int rpos = receive_pos;
+    if (len > sizeof(receive_buf) - rpos)
+        len = sizeof(receive_buf) - rpos;
+    memcpy(&receive_buf[rpos], data, len);
+    receive_pos = rpos + len;
+}
+
 void
 canbus_rx_task(void)
 {
@@ -185,6 +206,11 @@ canbus_rx_task(void)
         int ret = canbus_read(&id, data);
         if (ret < 0)
             break;
+        if (id && id == canbus_assigned_id)
+            can_process_data(id, ret, data);
+        if (id && id == canbus_assigned_id + 1)
+            can_id_conflict();
+        else if (id == CANBUS_ID_ADMIN)
             can_process(id, ret, data);
     }
 
@@ -209,14 +235,19 @@ DECL_TASK(canbus_rx_task);
  * Setup and shutdown
  ****************************************************************/
 
+void
+command_get_canbus_id(uint32_t *args)
+{
+    sendf("canbus_id canbus_uuid=%.*s canbus_nodeid=%u"
+          , sizeof(canbus_uuid), canbus_uuid, can_get_nodeid());
+}
+DECL_COMMAND_FLAGS(command_get_canbus_id, HF_IN_SHUTDOWN, "get_canbus_id");
+
 void
 canbus_set_uuid(void *uuid)
 {
     memcpy(canbus_uuid, uuid, sizeof(canbus_uuid));
     canbus_notify_rx();
-
-    // Send initial message
-    can_process_uuid(0, 0, NULL);
 }
 
 void

src/generic/canbus.h

@@ -3,16 +3,14 @@
 
 #include <stdint.h> // uint32_t
 
-#define CANBUS_ID_UUID 0x321
+#define CANBUS_ID_ADMIN 0x3f0
-#define CANBUS_ID_SET 0x322
+#define CANBUS_ID_ADMIN_RESP 0x3f1
-#define CANBUS_ID_UUID_RESP 0x323
 #define CANBUS_UUID_LEN 6
 
 // callbacks provided by board specific code
 int canbus_read(uint32_t *id, uint8_t *data);
 int canbus_send(uint32_t id, uint32_t len, uint8_t *data);
 void canbus_set_filter(uint32_t id);
-void canbus_reboot(void);
 
 // canbus.c
 void canbus_notify_tx(void);

src/stm32/can.c

@@ -159,43 +159,35 @@ canbus_send(uint32_t id, uint32_t len, uint8_t *data)
     return len;
 }
 
-#define CAN_FILTER_NUMBER 0
-
 // Setup the receive packet filter
 void
 canbus_set_filter(uint32_t id)
 {
-    uint32_t filternbrbitpos = 1 << CAN_FILTER_NUMBER;
-
     /* Select the start slave bank */
     SOC_CAN->FMR |= CAN_FMR_FINIT;
     /* Initialisation mode for the filter */
     SOC_CAN->FA1R = 0;
 
-    uint32_t idadmin = CANBUS_ID_UUID;
+    uint32_t mask = CAN_RI0R_STID | CAN_TI0R_IDE | CAN_TI0R_RTR;
-    SOC_CAN->sFilterRegister[CAN_FILTER_NUMBER].FR1 = idadmin << (5 + 16);
+    SOC_CAN->sFilterRegister[0].FR1 = CANBUS_ID_ADMIN << CAN_RI0R_STID_Pos;
-    SOC_CAN->sFilterRegister[CAN_FILTER_NUMBER].FR2 = id << (5 + 16);
+    SOC_CAN->sFilterRegister[0].FR2 = mask;
+    SOC_CAN->sFilterRegister[1].FR1 = (id + 1) << CAN_RI0R_STID_Pos;
+    SOC_CAN->sFilterRegister[1].FR2 = mask;
+    SOC_CAN->sFilterRegister[2].FR1 = id << CAN_RI0R_STID_Pos;
+    SOC_CAN->sFilterRegister[2].FR2 = mask;
 
-    /* Identifier list mode for the filter */
-    SOC_CAN->FM1R = filternbrbitpos;
     /* 32-bit scale for the filter */
-    SOC_CAN->FS1R = filternbrbitpos;
+    SOC_CAN->FS1R = (1<<0) | (1<<1) | (1<<2);
 
     /* FIFO 0 assigned for the filter */
     SOC_CAN->FFA1R = 0;
 
     /* Filter activation */
-    SOC_CAN->FA1R = filternbrbitpos;
+    SOC_CAN->FA1R = (1<<0) | (id ? (1<<1) | (1<<2) : 0);
     /* Leave the initialisation mode for the filter */
     SOC_CAN->FMR &= ~CAN_FMR_FINIT;
 }
 
-void
-canbus_reboot(void)
-{
-    NVIC_SystemReset();
-}
-
 // This function handles CAN global interrupts
 void
 CAN_IRQHandler(void)
@@ -292,7 +284,7 @@ can_init(void)
         ;
 
     /*##-2- Configure the CAN Filter #######################################*/
-    canbus_set_filter(CANBUS_ID_SET);
+    canbus_set_filter(0);
 
     /*##-3- Configure Interrupts #################################*/
     armcm_enable_irq(CAN_IRQHandler, CAN_RX0_IRQn, 0);