rpi_touchscreen_i2c_write
rpi_touchscreen_i2c_write(ts, REG_PWM, 0);
rpi_touchscreen_i2c_write(ts, REG_POWERON, 0);
rpi_touchscreen_i2c_write(ts, REG_POWERON, 1);
rpi_touchscreen_i2c_write(ts, REG_PWM, 255);
rpi_touchscreen_i2c_write(ts, REG_PORTA, BIT(2));
rpi_touchscreen_i2c_write(ts, REG_POWERON, 0);