Improve reboot and enter REPL reliability

circuitpython_kernel/board.py

@@ -1,19 +1,23 @@
 # -*- coding: utf-8 -*-
 """Serial Connection to a Board"""
 import logging
+import time
 from serial import Serial
 from serial.tools.list_ports import comports
 from serial.serialutil import SerialException
 
 # Create BOARD_LOGGER for debug messages.
 BOARD_LOGGER = logging.getLogger(__name__)
 
+# Timeouts
+ENTER_REPL_TIMEOUT = 5.0
+REBOOT_WAIT = 0.5
 
 # Vendor IDs
-ADAFRUIT_VID = 0x239A # SAMD
-ESP8266_VID = 0x10C4 # Huzzah ESP8266
-PICO_VID = 0x239A # PICO PI
-TEENSY_VID = 0x16C0 #PJRC Teensy 4.1
+ADAFRUIT_VID = 0x239A  # SAMD
+ESP8266_VID = 0x10C4  # Huzzah ESP8266
+PICO_VID = 0x239A  # PICO PI
+TEENSY_VID = 0x16C0  # PJRC Teensy 4.1
 
 # repl commands
 CHAR_CTRL_A = b'\x01'
@@ -24,9 +28,12 @@
 # repl messages
 MSG_NEWLINE = b"\r\n"
 MSG_RAWREPL = b"raw REPL; CTRL-B to exit"
-MSG_RAWREPL_PROMPT = b"\r\n>"
+MSG_RAWREPL_BARE_PROMPT = b">"
+MSG_RAWREPL_PROMPT = MSG_NEWLINE + MSG_RAWREPL_BARE_PROMPT
 MSG_SOFT_REBOOT = b'soft reboot\r\n'
 MSG_RELOAD = b'Use CTRL-D to reload.'
+MSG_AUTORELOAD = b'Auto-reload is on.'
+
 
 class BoardError(Exception):
     """Errors relating to board connections"""
@@ -51,7 +58,6 @@ def write(self, msg):
             self.connected = False
             raise BoardError(f"cannot write to board: {serial_error}")
 
-
     def read_until(self, msg):
         """Reads board until end of `msg`.
         """
@@ -61,6 +67,21 @@ def read_until(self, msg):
             self.connected = False
             raise BoardError(f"cannot read from board: {serial_error}")
 
+    def read_until_any(self, *msgs):
+        """Reads board until the tokens `msgs`.
+        """
+        content = bytearray()
+        while True:
+            try:
+                got = self.serial.read(1)
+            except SerialException as serial_error:
+                self.connected = False
+                raise BoardError(f"cannot read from board: {serial_error}")
+
+            content.extend(got)
+            for msg in msgs:
+                if content.endswith(msg):
+                    return content
 
     def read_all(self):
         """Attempts to read all incoming msgs from board.
@@ -85,29 +106,43 @@ def softreset(self):
         """Resets the circuitpython board (^D)
         from a jupyter cell.
         """
-        serial = self.serial
         # in case the VM is in a weird state ...
         self.enter_raw_repl()
         # now do the soft reset ...
         BOARD_LOGGER.debug("* ^D, soft reset")
-        serial.write(CHAR_CTRL_D)
-        serial.read_until(MSG_SOFT_REBOOT)
-        serial.read_until(MSG_RELOAD)
-        serial.write(b'\n')
-        serial.read_until(MSG_RAWREPL)
-        serial.read_until(MSG_RAWREPL_PROMPT)
+        self.write(CHAR_CTRL_D)
+        self.read_until(MSG_SOFT_REBOOT)
+        BOARD_LOGGER.debug("* waiting for fresh boot ...")
+        self.read_until_any(MSG_RELOAD, MSG_AUTORELOAD)
+        BOARD_LOGGER.debug("* saw boot message, sleeping before interrupt ...")
+        time.sleep(REBOOT_WAIT)
+        self.enter_raw_repl()
         BOARD_LOGGER.debug("* soft reset complete, in raw repl")
 
     def enter_raw_repl(self):
         """Enters the RAW circuitpython repl.
         """
         BOARD_LOGGER.debug('* enter raw repl ...')
-        serial = self.serial
-        serial.write(CHAR_CTRL_C)
-        serial.write(CHAR_CTRL_A)
-        # wait for prompt
-        serial.read_until(MSG_RAWREPL)
-        serial.read_until(MSG_RAWREPL_PROMPT)
+        self.write(CHAR_CTRL_C)
+        self.write(CHAR_CTRL_A)
+        BOARD_LOGGER.debug('* waiting for prompt ...')
+        # just waiting for the ">" prompt, but sometimes there may be other
+        # text before it, which includes a ">", so read_until isn't correct.
+        start = time.monotonic()
+        while True:
+            msg = self.read_all()
+
+            if not msg:
+                if time.monotonic() - start > ENTER_REPL_TIMEOUT:
+                    raise BoardError("no response from board")
+                time.sleep(0.01)
+                continue
+
+            BOARD_LOGGER.debug(f"got: {msg}")
+
+            if msg.endswith(MSG_RAWREPL_BARE_PROMPT):
+                break
+
         BOARD_LOGGER.debug('* entered raw repl, returning to kernel...')
 
     def connect(self):
@@ -120,8 +155,8 @@ def connect(self):
         try:
             BOARD_LOGGER.debug(f'connect: open {device}')
             self.serial = Serial(device, 115200, parity='N')
-        except:
-            raise BoardError(f"failed to access {device}")
+        except Exception as e:
+            raise BoardError(f"failed to access {device}: {e}")
         # open the port
         if not self.serial.is_open:
             try:
@@ -137,17 +172,18 @@ def connect(self):
         try:
             self.enter_raw_repl()
             self.connected = True
-        except:
-            raise BoardError(f"failed to enter raw repl with {device}")
-
+        except Exception as e:
+            raise BoardError(f"failed to enter raw repl with {device}: {e}")
 
     def _find_board(self):
         """Find serial port where an Adafruit board is connected"""
         for port in comports():
             # print out each device
             BOARD_LOGGER.debug(port.device)
-            if port.vid == ADAFRUIT_VID or port.vid == ESP8266_VID or port.vid == PICO_VID or port.vid == TEENSY_VID:
-                BOARD_LOGGER.debug(f"CircuitPython Board Found at: {port.device}")
+            if port.vid == ADAFRUIT_VID or port.vid == ESP8266_VID or \
+                    port.vid == PICO_VID or port.vid == TEENSY_VID:
+                BOARD_LOGGER.debug(
+                    f"CircuitPython Board Found at: {port.device}")
                 BOARD_LOGGER.debug(f"Connected? {self.connected}")
                 return port.device
         raise BoardError("found no board")