How can I connect a drive activity LED to the SCSI bus?
If you want an LED to show when a drive is being accessed, you need to connect the LED to a pair of pins designated on the particular drive for that purpose. No one signal on the SCSI bus indicates drive activity. The bus goes through many phases in the process of accessing a device, and signals are re-used for multiple purposes. While you could design a logic circuit that decoded the SCSI signals and activated an LED at the right time, it is way too much work to do it that way.
