root@h3ulcb:~# cansend sllin0 030#FFFFFFF0FF010000

root@h3ulcb:~# cansend sllin0 030#000000F000010000

root@h3ulcb:~# 



static int write_can(afb_api_t api)
{
    json_object *jresp = json_object_new_object();
    json_object *jobj = json_object_new_object();
    json_object *jarray = json_object_new_array();

    json_object_object_add(jresp, "bus_name", json_object_new_string("ls"));
    json_object_object_add(jresp, "frame", jobj);

    json_object_object_add(jobj, "can_id", json_object_new_int(0x30));
    json_object_object_add(jobj, "can_dlc", json_object_new_int(8));


    json_object_array_add(jarray,
        json_object_new_int(to_can_temp(read_temp_left_zone())));

    json_object_array_add(jarray,
        json_object_new_int(to_can_temp(read_temp_right_zone())));

    json_object_array_add(jarray,
        json_object_new_int(to_can_temp(read_temp())));

    json_object_array_add(jarray, json_object_new_int(0xf0));
    json_object_array_add(jarray, json_object_new_int(read_fanspeed()));
    json_object_array_add(jarray, json_object_new_int(1));
    json_object_array_add(jarray, json_object_new_int(0));
    json_object_array_add(jarray, json_object_new_int(0));

    json_object_object_add(jobj, "can_data", jarray);

    return afb_api_call_sync(api, "low-can", "write", jresp, NULL, NULL, NULL);
}



So .... 

030# aa bb cc dd ee ff gg hh

where "aa" == '20'   Temp left
where "bb" == '24'   temp right
where "cc" == '22'          # average of aa and bb   (uint8_t)(((int)read_temp_left_zone() + (int)read_temp_right_zone()) >> 1);
where "dd" == 'F0'
where "ee" == 'FF'          # full fan speed
where "ff" == '01'   1
where "gg" == '00'   0
where "gg" == '00'   0