+    hal_float_t *commandvds;   /* pin: commanded derivative dummysig */
+    hal_float_t *commandv;     /* pin: commanded derivative value */
+    hal_float_t *feedbackvds;  /* pin: feedback derivative dummysig */
+    hal_float_t *feedbackv;    /* pin: feedback derivative value */

+    /* compute command and feedback derivatives to dummysigs */
+    *(pid->commandvds) = (command - pid->prev_cmd) * periodrecip;
+    *(pid->feedbackvds) = (feedback - pid->prev_fb) * periodrecip;
+    /* and calculate derivative term as difference of derivatives */
+    *(pid->error_d) = *(pid->commandv) - *(pid->feedbackv);

+    retval = hal_pin_float_newf(HAL_IN, &(addr->feedbackv), comp_id,
+                               "pid.%d.feedback-deriv", num);
+    if (retval != 0) {
+       return retval;
+    }
+    addr->feedbackvds = addr->feedbackv;