ganglion: fix bug with bit shift in decompression

Author: jfrey-xx

open_bci_ganglion.py

@@ -458,8 +458,6 @@ def conv19bitToInt32 (threeByteBuffer):
 
   return (prefix << 19) | (threeByteBuffer[0] << 16) | (threeByteBuffer[1] << 8) | threeByteBuffer[2]
 
-
-
 def decompressDeltas19Bit(buffer):
   """
   Called to when a compressed packet is received.
@@ -468,63 +466,63 @@ def decompressDeltas19Bit(buffer):
   """ 
   if len(buffer) != 19:
     raise ValueError("Input should be 19 bytes long.")
-
+  
   receivedDeltas = [[0, 0, 0, 0],[0, 0, 0, 0]]
 
   # Sample 1 - Channel 1
   miniBuf = [
       (buffer[0] >> 5),
-      ((buffer[0] & 0x1F) << 3) | (buffer[1] >> 5),
-      ((buffer[1] & 0x1F) << 3) | (buffer[2] >> 5)
+      ((buffer[0] & 0x1F) << 3 & 0xFF) | (buffer[1] >> 5),
+      ((buffer[1] & 0x1F) << 3 & 0xFF) | (buffer[2] >> 5)
     ]
 
   receivedDeltas[0][0] = conv19bitToInt32(miniBuf)
 
   # Sample 1 - Channel 2
   miniBuf = [
       (buffer[2] & 0x1F) >> 2,
-      (buffer[2] << 6) | (buffer[3] >> 2),
-      (buffer[3] << 6) | (buffer[4] >> 2)
+      (buffer[2] << 6 & 0xFF) | (buffer[3] >> 2),
+      (buffer[3] << 6 & 0xFF) | (buffer[4] >> 2)
     ]
   receivedDeltas[0][1] = conv19bitToInt32(miniBuf)
 
   # Sample 1 - Channel 3
   miniBuf = [
-      ((buffer[4] & 0x03) << 1) | (buffer[5] >> 7),
-      ((buffer[5] & 0x7F) << 1) | (buffer[6] >> 7),
-      ((buffer[6] & 0x7F) << 1) | (buffer[7] >> 7)
+      ((buffer[4] & 0x03) << 1 & 0xFF) | (buffer[5] >> 7),
+      ((buffer[5] & 0x7F) << 1 & 0xFF) | (buffer[6] >> 7),
+      ((buffer[6] & 0x7F) << 1 & 0xFF) | (buffer[7] >> 7)
     ]
   receivedDeltas[0][2] = conv19bitToInt32(miniBuf)
 
   # Sample 1 - Channel 4
   miniBuf = [
       ((buffer[7] & 0x7F) >> 4),
-      ((buffer[7] & 0x0F) << 4) | (buffer[8] >> 4),
-      ((buffer[8] & 0x0F) << 4) | (buffer[9] >> 4)
+      ((buffer[7] & 0x0F) << 4 & 0xFF) | (buffer[8] >> 4),
+      ((buffer[8] & 0x0F) << 4 & 0xFF) | (buffer[9] >> 4)
     ]
   receivedDeltas[0][3] = conv19bitToInt32(miniBuf)
 
   # Sample 2 - Channel 1
   miniBuf = [
       ((buffer[9] & 0x0F) >> 1),
-      (buffer[9] << 7) | (buffer[10] >> 1),
-      (buffer[10] << 7) | (buffer[11] >> 1)
+      (buffer[9] << 7 & 0xFF) | (buffer[10] >> 1),
+      (buffer[10] << 7 & 0xFF) | (buffer[11] >> 1)
     ]
   receivedDeltas[1][0] = conv19bitToInt32(miniBuf)
 
   # Sample 2 - Channel 2
   miniBuf = [
-      ((buffer[11] & 0x01) << 2) | (buffer[12] >> 6),
-      (buffer[12] << 2) | (buffer[13] >> 6),
-      (buffer[13] << 2) | (buffer[14] >> 6)
+      ((buffer[11] & 0x01) << 2 & 0xFF) | (buffer[12] >> 6),
+      (buffer[12] << 2 & 0xFF) | (buffer[13] >> 6),
+      (buffer[13] << 2 & 0xFF) | (buffer[14] >> 6)
     ]
   receivedDeltas[1][1] = conv19bitToInt32(miniBuf)
 
   # Sample 2 - Channel 3
   miniBuf = [
       ((buffer[14] & 0x38) >> 3),
-      ((buffer[14] & 0x07) << 5) | ((buffer[15] & 0xF8) >> 3),
-      ((buffer[15] & 0x07) << 5) | ((buffer[16] & 0xF8) >> 3)
+      ((buffer[14] & 0x07) << 5 & 0xFF) | ((buffer[15] & 0xF8) >> 3),
+      ((buffer[15] & 0x07) << 5 & 0xFF) | ((buffer[16] & 0xF8) >> 3)
     ]
   receivedDeltas[1][2] = conv19bitToInt32(miniBuf)