## SITL in gazebo 8 with ArduCopterPlugin
SITL (software in the loop) simulator allows you to run betaflight/cleanflight without any hardware.
Currently only tested on Ubuntu 16.04, x86_64, gcc (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609.

### install gazebo 8
see here: [Installation](http://gazebosim.org/tutorials?cat=install)

### copy & modify world
for Ubunutu 16.04:
`cp /usr/share/gazebo-8/worlds/iris_arducopter_demo.world .`

change `real_time_update_rate` in `iris_arducopter_demo.world`:
`<real_time_update_rate>0</real_time_update_rate>`
to
`<real_time_update_rate>100</real_time_update_rate>`
***this suggest set to non-zero***

`100` mean what speed your computer should run in (Hz).
Faster computer can set to a higher rate.
see [here](http://gazebosim.org/tutorials?tut=modifying_world&cat=build_world#PhysicsProperties) for detail.
`max_step_size` should NOT higher than `0.0025` as I tested.
smaller mean more accurate, but need higher speed CPU to run as realtime.

### build betaflight
run `make TARGET=SITL`

### settings
to avoid simulation speed slow down, suggest to set some settings belows:

In `configuration` page:

1. `ESC/Motor`: `PWM`, disable `Motor PWM speed Sparted from PID speed`
2. `PID loop frequency` as high as it can.

### start and run
1. start betaflight: `./obj/main/betaflight_SITL.elf`
2. start gazebo: `gazebo --verbose ./iris_arducopter_demo.world`
4. connect your transmitter and fly/test, I used a app to send `MSP_SET_RAW_RC`, code available [here](https://github.com/cs8425/msp-controller).

### note
betaflight	->	gazebo	`udp://127.0.0.1:9002`
gazebo	->	betaflight	`udp://127.0.0.1:9003`

UARTx will bind on `tcp://127.0.0.1:576x` when port been open.

`eeprom.bin`, size 8192 Byte, is for config saving.
size can be changed in `src/main/target/SITL/parameter_group.ld` >> `__FLASH_CONFIG_Size`


