   Serial.println("SecureSmallFrameEncoding");
   uint8_t buf[OTRadioLink::SecurableFrameHeader::maxSmallFrameSize];
   //Example 3: secure, no valve, representative minimum stats {"b":1}).
-  //In this case the frame sequence number is zero,
+  //Note that the sequence number must match the 4 lsbs of the message count, ie from iv[11].
   //and the ID is 0xaa 0xaa 0xaa 0xaa (transmitted) with the next ID bytes 0x55 0x55.
   //ResetCounter = 42
   //TxMsgCounter = 793
   //(Thus nonce/IV: aa aa aa aa 55 55 00 00 2a 00 03 19)
   //
-  //3e cf 04 aa aa aa aa 20 | b3 45 f9 29 69 57 0c b8 28 66 14 b4 f0 69 b0 08 71 da d8 fe 47 c1 c3 53 83 48 88 03 7d 58 75 75 | 00 00 2a 00 03 19 97 5b da df 92 08 42 b8 c1 3b dc 02 76 54 cb 8d 80 
-  //
+  //3e cf 94 aa aa aa aa 20 | b3 45 f9 29 69 57 0c b8 28 66 14 b4 f0 69 b0 08 71 da d8 fe 47 c1 c3 53 83 48 88 03 7d 58 75 75 | 00 00 2a 00 03 19 29 3b 31 52 c3 26 d2 6d d0 8d 70 1e 4b 68 0d cb 80
   //
   //3e  length of header (62) after length byte 5 + (encrypted) body 32 + trailer 32
   //cf  'O' secure OpenTRV basic frame

  //... b3 45 f9 29 69 57 0c b8 28 66 14 b4 f0 69 b0 08 71 da d8 fe 47 c1 c3 53 83 48 88 03 7d 58 75 75 | ...
  AssertIsEqual(0xb3, buf[8]); // 1st byte of encrypted body.
  AssertIsEqual(0x75, buf[39]); // 32nd/last byte of encrypted body.
  //... 00 00 2a 00 03 19 97 5b da df 92 08 42 b8 c1 3b dc 02 76 54 cb 8d 80
  AssertIsEqual(0x00, buf[40]); // 1st byte of counters.
  AssertIsEqual(0x00, buf[41]);
  AssertIsEqual(0x2a, buf[42]);
  AssertIsEqual(0x00, buf[43]); 
  AssertIsEqual(0x03, buf[44]);
  AssertIsEqual(0x19, buf[45]); // Last byte of counters.
  AssertIsEqual(0x97, buf[46]); // 1st byte of tag.
  AssertIsEqual(0x8d, buf[61]); // 16th/last byte of tag.
  AssertIsEqual(0x80, buf[62]); // enc format.
  // To decode, emulating RX, structurally validate unpack the header and extract the ID.
  OTRadioLink::SecurableFrameHeader sfhRX;

  //b3 45 f9 ... 58 75 75  32 bytes of encrypted body
  //00 00 2a  reset counter
  //00 03 19  message counter
  //29 3b 31 ... 68 0d cb  16 bytes of authentication tag
  //80  enc/auth type/format indicator.
  // Preshared ID prefix; only an initial part/prefix of this goes on the wire in the header.
  const uint8_t id[] = { 0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55 };
