5.2 Fan and GPO Commands
5.2.1 General Purpose Output Off (254 86 [gpo #])
This command turns OFF any of the general purpose outputs. [gpo #] is 1 to 6.
5.2.2 General Purpose Output On (254 87 [gpo #])
This command turns ON any of the general purpose outputs. [gpo #] is 1 to 6.
5.2.3 PWM Value (254 192 [fan #] [PWM value])
This command sets one of the high power GPOs (GPOs 1-4) into PWM mode. This permits speed
control of a fan. A PWM value of 0 is off, 128 is 50% power, and 255 is full power. The fan# can be 1 to 3.
5.2.4 Return Fan RPM (254 193 [fan #])
This command will return a packet to the host with the fan RPM contained in it. The structure of the fan
is described in the Table below.
Table 13: Return RPM Structure
Offset Size
Description
0
2
0x232A
2
1
0x03
3
1
0x52
4
1
Fan #
5
2
Fan Period (MSB first)
To convert the fan period into an RPM value, follow the following formula;
RPM
=
18750000
X
∗
n
Where
X
is the fan period, and
n
is the number of ticks that the fan produces per period. The number of
ticks is usually 1, 2 or 4. For unknown fans some experimentation is required.
NOTE
It is not recommended that the RPM is checked more than once every two seconds.
If the RPM is checked more frequently, the actual RPM readings can become very erratic.
Matrix Orbital
LK204-24-USB
23
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