snekde: Support 57600 and 115200 baud

8MHz atmega devices cannot use 115200 baud because the clock
resolution isn't fine enough to get a close match in bit rate. So,
those devices will run at 57600 baud instead. Support this by adding a
baud rate selection key (F8) which switches between 115200 and 57600
baud. Display this in the status bar along with the device name.

Signed-off-by: Keith Packard <keithp@keithp.com>

snekde/snekde.py

@@ -49,6 +49,10 @@
 
 snek_debug_file = False
 
+baud_rates = [57600, 115200]
+
+baud_selection = 1
+
 
 def snek_debug(message):
     global snek_debug_file
@@ -185,7 +189,7 @@ class SnekDevice:
     # that gets data that are read
     #
 
-    def __init__(self, port, interface):
+    def __init__(self, port, interface, rate=115200):
         self.interface = interface
         self.device = port.device
 
@@ -195,7 +199,6 @@ def __init__(self, port, interface):
         self.synchronous_put = True
         self.synchronous_limit = 16
 
-        rate = 115200
         for port_mod in port_mods:
             if port_mod in port.description or port_mod in port.hwid:
                 if "async" in port_mods[port_mod]:
@@ -345,6 +348,12 @@ def write(self, data):
     def command(self, data, intr="\x03"):
         self.write("\x0e" + intr + data)
 
+    def set_baud(self, baud):
+        self.serial.baudrate = baud
+        if self.serial.is_open:
+            self.serial.close()
+            self.serial.open()
+
 
 class EditWin:
     """Editable text object"""
@@ -1112,6 +1121,7 @@ def screen_get_sizes():
     ("F5", "Load"),
     ("F6", "Save"),
     ("F7", "Switch"),
+    ("F8", "Rate"),
 )
 
 # Paint the function key help text and the separator line
@@ -1128,6 +1138,7 @@ def screen_paint():
     device_name = "<no device>"
     if snek_device:
         device_name = snek_device.device
+    device_name = "%s %d" % (device_name, baud_rates[baud_selection])
     device_col = snek_cols - len(device_name)
     if device_col < 0:
         device_col = 0
@@ -1190,14 +1201,22 @@ def screen_fini():
     curses.endwin()
 
 
+def switch_baud():
+    global snek_device, baud_selection, baud_rates
+    baud_selection = (baud_selection + 1) % len(baud_rates)
+    if snek_device:
+        snek_device.set_baud(baud_rates[baud_selection])
+    screen_paint()
+
+
 def snekde_open_device():
     global snek_device, snek_monitor
     dialog = GetPortWin()
     port = dialog.run_dialog()
     if not port:
         return
     try:
-        device = SnekDevice(port, snek_monitor)
+        device = SnekDevice(port, snek_monitor, rate=baud_rates[baud_selection])
         device.start()
         if snek_device:
             snek_device.close()
@@ -1333,6 +1352,8 @@ def run():
                 snek_current_window = snek_repl_win
             else:
                 snek_current_window = snek_edit_win
+        elif ch == curses.KEY_F8 or ch == ord("8") | 0x80:
+            switch_baud()
         elif ch == ord("\n"):
             if snek_current_window is snek_edit_win:
                 snek_current_window.dispatch(ch)