Using params within px4io mixer. Possible?

smgoza · June 26, 2017, 12:25pm

I would like to use parameters inside of the px4io mixer code in C++. I’ve read the docs showing param_get() and param_find(). My problem is that it cannot find those functions when I try to compile. I include the systemlib/param/param.h (done from memory so may not be correctly spelled). When I compile it complains it can’t find the reference to the function. Basically it can’t find the code. Is there a library I’m supposed to link to? Do I include the param.c into the CMake file? Or the more basic question… Am I allowed to use params in the mixer since it is in a different processor?

Any help would be appreciated!
Mike

maruseru · June 27, 2017, 1:10pm

I guess it would be pointless to include the parameter files because the px4io mixer.cpp is running on a different MCU so you couldn’t access these parameters.
You can have a look at the PX4IO (px4io.cpp) driver. I think you could send custom parameters via “io_reg_set()” to the second MCU.

For example:

github.com

PX4/Firmware/blob/master/src/drivers/px4io/px4io.cpp#L1117


					float pval;


					/* fetch the trim values from parameters */
					sprintf(pname, "PWM_MAIN_TRIM%u", i + 1);
					param_t param_h = param_find(pname);


					if (param_h != PARAM_INVALID) {


						param_get(param_h, &pval);
						pwm_values.values[i] = (int16_t)(10000 * pval);
					}
				}


				/* copy values to registers in IO */
				ret = io_reg_set(PX4IO_PAGE_CONTROL_TRIM_PWM, 0, pwm_values.values, _max_actuators);


				float param_val;
				param_t parm_handle;


				parm_handle = param_find("TRIM_ROLL");