Alpha Omega Instruments 800 Series - Troubleshooting; Common Issues and Solutions; Points of Clarification

Loop Back Command (0x08)
This command simply echoes the message. This serves as a quick way to check
your wiring.
Packet sent to controller:
nn nnnn nn08nn
controller address (one byte)
loop back command (0x08)
data high byte
data low byte
CRC low byte
CRC high byte
Example: Run loop back test on controller at address 40 (0x28).
Sent: 28 08 55 66 77 88 31 B7
Received: 28 08 55 66 77 88 31 B7
ALPHA OMEGA INSTRUMENTS CORP. Instruction Manual
Series 800/850 Thermoelectric Cooler Controller Page 107