Sharp ASK Protocol Description

Infrared Characteristics

Transmission distance	less than 1 meter
Carrier	infrared 900 - 1050 nm peak
Subcarrier	500KHz (450 - 550KHz)
Modulation	ASK

Communications Specification

Baud Rate	9600 bps
Data Length	8 bits
Parity	Odd
Stop Bits	1

Protocol - Data Packets

Field	Value	Length	Comments
Sync Dummy	0x00	5	Receivers wait for 0x00 0x00 0x96
Start ID	0x96	1
ID Code 1	0x81 or 0x91	1	bits 7-4 are target equipment type, bits 3-0 are type of packet
Version Number	0x10	1	Only bits 7-4 should be checked by receiver
Block Number	0x0001 - 0xffff	2	Last block always 0xffff (low/high)
Control Code	0x01	1	Not checked by receiver
Device Code	0x40	1
ID Code 2	0xfe	1
Data Length	0x0000 - 0x0200	2	If data is exactly 512 bytes, two packets are required, with 0 bytes in second packet.
Data		0 - 512
Check Sum		2	Check sum of data part (low/high)

Protocol - Control Packets

Protocol

Annotations

1. Sending Side
   Send ENQ every 0.5 seconds waiting for SYN for normally 6 minutes (in case of a retry process, 10 seconds). If CAN is received or no answer is received, the sending side aborts data transmission. If any other data is received, the sending side moves to a retry process.

2. Receiving Side
   Wait for ENQ for normally 6 minutes (in case of a retry process, 10 seconds). If no ENQ is received, the receiving side aborts data transmission.

3. Receiuing Side
   SYN must be sent within 0.3 seconds after receiving ENQ. If the receiving side wants to abort data transmission, it should send CAn instead of SYN.

4. Receiving Side
   If no Data packet is received within 0.4 seconds after sending SYNs the receiving side moves to a retry process.

5. Sending Side
   Sending side must start sending Data packet within 0.2 seconds after receiving SYN.

6. Receiving Side
   ACK must be sent within 0.4 seconds after receiving the last byte of the Data packet.

7. Sending side
   If ACK is not received within 1 second or other data (including NACK) is received, the sending side moves to a retry process.

8. Sending side
   The sending side must finish sending one Data packet within 4 seconds.

   Receiving side
   If the last byte of the Data packet is not received within 5 seconds after receiving the first byte of the packet, the receiving side moves to a retry process. If a communication error is detected, the receiving side must skip all received data until:

   • no more data is received for 0.4 seconds or
   • 5 seconds pass after receiving the first byte of the packet, and then moves to a retry process.

   In case of a checksum error, send NACK within 0.4 seconds and move to a retry process ...

9. Sending and Receiving side
   If a communication error occurs, both sides try to transfer the same block again (retry process). The sending side backs to the stage of sending ENQ, the receiving side backs to the stage of receiving ENQ. In this case, the time-out (6 minutes) is reduced to 10 seconds. Retry process must be performed within 1 second after the communication error is confirmed. Retry process can be done up to 2 times (3 times in total).

Notes

1. Continuous two bytes in one packet must be sent within 0.2 seconds, If continuous two bytes are not received within 0.4 seconds the receive side should detect a communications error.

2. Switching from send mode to receive mode must be done within 2 milliseconds.. In other words, equipment must be ready for receiving data within 2 milliseconds after sending the last byte. No data must be sent within 3 milliseconds after receiving the last byte.

3. Each packet (both Data and Control) is considered to start when continuous 3 bytes (OOh, OOh, 96h) are detected. Other data are ignored before detecting these continuous 3 bytes.

4. If a non-sequential block number (i.e., a value other than the last block number received + 1 or OFFFFh) is received in the Block No. field, the receiving side should detect an error and start a retry process. It is also the sam case when the same Block No. as the previous one is received (this will happen if the sending side cannot receive ACK from the receiving side).