i have a promise sata four port controller. it has a four pin output for hard drive activity. from what i can tell two of the pins are 'idle' at about 3.3v and the other two at 2v, approx. i've figured out, using a multimeter, that when there's drive activity the two 2v pins drop to 0v, but that's about all i can tell. my sata drives are in a raid 5 config, which of course makes independently testing them somewhat difficult. anyway, i'm trying to figure out how to 'read' the led signals (ultimately so i can hook it up to four leds). any institutional knowledge on this, so i don't have to hook up four seperate drives and test each with every pin combination?
My guess is that there's only two drive activity LEDs. Anode goes to the leads that stay at 2v, cathode goes to the leads that change voltage. I know you were looking for 4 activity LEDs, but that'd require at the very least an extra pin (common anode + 1 cathode pin for each LED) and a small PCB to distribute the common power to the LEDs.
I've a suspicion the 2V you measured is the forward voltage of the LED, and it's possibly a current-limited 5V being switched. But I know SFA about SATA.
Is that a 2410SA? I know there's a jumper but I didn't realises it was meant to be activiity. Though it was for their own diagnostics.
i'm measuring voltage just between the pin and ground, i.e., with no led in the circuit. its the tx4, the manual indicates that those are for disk activity, but gives no other info. i think whypick1 may be right that there only two monitors which provide 1.3v (3.3 minus 2) at idle and the full 3.3 during activity. oh well . . .
The card is using a negative logic. The 3.3v is Vcc and the 2v pin is the control, which is left floating with an open... it may read anywhere from 1.5-2.8v. When a drive on the respective IDE channel is active, then the floating pin will have a ground (or more accurately a logic 0) applied and allow the LED to light. This means you have one LED per IDE channel (max two drives per channel). If you want to have an LED for each drive, you are going to have to do some modding and quite a bit of wiring-- IDE pin 39 is the Drive Activity pin... the drive applies a low to this pin when active. In order to get a drive activity light for each drive you need to wire an LED to pin 39 of each drive. Here is an example of one such mod.
controller and drives are sata . . . but, your general point that there are only two led circuits seems right, so there's no way i'm pulling four drives' led info from those four pins. oh well . . .
