diff --git a/mbv/prog.py b/mbv/prog.py
index c8508f0..693a5ba 100644
--- a/mbv/prog.py
+++ b/mbv/prog.py
@@ -6,33 +6,33 @@ import threading
 import time
 
 offset = 0x80000000
-tty = '/dev/ttyUSB1'
+tty = "/dev/ttyUSB1"
 baud = 115200
 chunksize = 1024
 
 
 def write(s, offset, dat):
     for i in range(0, len(dat), chunksize):
-        chunk = dat[i: i + chunksize]
-        cmd = struct.pack('<cII', b'c', offset + i, len(chunk))
+        chunk = dat[i : i + chunksize]
+        cmd = struct.pack("<cII", b"c", offset + i, len(chunk))
 
-        print(f'Sending {len(chunk)} bytes @0x{offset + i:04x}')
+        print(f"Sending {len(chunk)} bytes @0x{offset + i:04x}")
 
         s.write(cmd)
         s.write(chunk)
 
         ack = s.read(2)
         if len(ack) < 2:
-            raise RuntimeError(f'timeout waiting for full ack. got {ack}')
-        if ack[0] != b'a'[0]:
-            raise RuntimeError(f'expected ack, got this instead: {ack}')
-        print(f'Ack! len={ack[1]}')
+            raise RuntimeError(f"timeout waiting for full ack. got {ack}")
+        if ack[0] != b"a"[0]:
+            raise RuntimeError(f"expected ack, got this instead: {ack}")
+        print(f"Ack! len={ack[1]}")
 
 
 def jump(s, offset):
-        cmd = struct.pack('<cI', b'j', offset)
-        print(f'Jumping to 0x{offset:04x}')
-        s.write(cmd)
+    cmd = struct.pack("<cI", b"j", offset)
+    print(f"Jumping to 0x{offset:04x}")
+    s.write(cmd)
 
 
 def stream_logs(s):
@@ -40,21 +40,25 @@ def stream_logs(s):
         dat = s.read()
         if not dat:
             continue
-        sys.stdout.buffer.write(dat.replace(b'\r', b''))
+        sys.stdout.buffer.write(dat.replace(b"\r", b""))
         sys.stdout.buffer.flush()
 
 
 def parse_args():
     parser = argparse.ArgumentParser()
     parser.add_argument("binary")
-    parser.add_argument("--monitor", action="store_true",
-                        help="wait for and display program serial output")
+    parser.add_argument(
+        "--monitor",
+        action="store_true",
+        help="wait for and display program serial output",
+    )
     return parser.parse_args()
 
+
 def main():
     args = parse_args()
 
-    with open(args.binary, 'rb') as f:
+    with open(args.binary, "rb") as f:
         dat = f.read()
 
     s = serial.Serial(tty, baud, timeout=1)
@@ -67,7 +71,7 @@ def main():
 
         try:
             while True:
-                dat = input("") + '\r'
+                dat = input("") + "\r"
                 s.write(dat.encode())
         except KeyboardInterrupt:
             print("Bye.")