Matrix Orbital PK202-24-USB - Manual (Page 27)

Table 12: 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.
5.2.5 Remember GPO / PWM State (254 195 [fan #] [PWM value])
This command will set the startup state for all the GPOs. When the device is powered up the next time,
the GPOs will be set to the values from this command. For GPOs 1 to 3 it behaves exactly as the PWM Value
command. For GPOs 4 to 6, a non-zero value for the PWM value make the GPO on for future startups. A
PWM value of 0 will result in the GPO being off.
This command does not affect the current state of the GPOs or fans, just power up.
5.2.6 Set PWM Base Frequency (254 196 [index])
NOTE This command was added in Firmware Version 2.1. It is not present in previous
versions.
This command sets the base frequency for the PWM modulation. The index selects a present frequency as
shown in the following Table.
Matrix Orbital PK202-24-USB 23