Fan control

Control external fan by switching GPIO 15 (defined as POWER_PIN in source code). Fan with nominal voltage 12V is powered by step-up converter.

Compilation

g++ -o fancontrol fancontrol.cpp

Temperature

CPU temperature is read from '/sys/class/thermal/thermal_zone0/temp' file

Rock Pi 4 connector

ROCK Pi 4 has a 40-pin expansion header.

GPIO number	Function2	Function1	GPIO	Pin#		Pin#	GPIO	Function1	Function2	GPIO number
		+3.3V		1		2		+5.0V
71		I2C7_SDA	GPIO2_A7	3		4		+5.0V
72		I2C7_SCL	GPIO2_B0	5		6		GND
75		SPI2_CLK	GPIO2_B3	7		8	GPIO4_C4	UART2_TXD		148
		GND		9		10	GPIO4_C3	UART2_RXD		147
146		PWM0	GPIO4_C2	11		12	GPIO4_A3	I2S1_SCLK		131
150		PWM1	GPIO4_C6	13		14		GND
149		SPDIF_TX	GPIO4_C5	15		16	GPIO4_D2			154
		+3.3V		17		18	GPIO4_D4			156
40	UART4_TXD	SPI1_TXD	GPIO1_B0	19		20		GND
39	UART4_RXD	SPI1_RXD	GPIO1_A7	21		22	GPIO4_D5			157
41		SPI1_CLK	GPIO1_B1	23		24	GPIO1_B2	SPI1_CSn		42
		GND		25		26		ADC_IN0
64		I2C2_SDA	GPIO2_A0	27		28	GPIO2_A1	I2C2_CLK		65
74	I2C6_SCL	SPI2_TXD	GPIO2_B2	29		30		GND
73	I2C6_SDA	SPI2_RXD	GPIO2_B1	31		32	GPIO3_C0	SPDIF_TX	UART3_CTSn	112
76		SPI2_CSn	GPIO2_B4	33		34		GND
133		I2S1_LRCK_TX	GPIO4_A5	35		36	GPIO4_A4	I2S1_LRCK_RX		132
158			GPIO4_D6	37		38	GPIO4_A6	I2S1_SDI		134
		GND		39		40	GPIO4_A7	I2S1_SDO		135