# FSIO 

The content below is from 2018 and is in the process of being updated. 

Flexible Logic is the fanciest-schmanciest feature of rusEfi.

For FSIO, rusEfi console provides a better user experience due to automated human to RPN conversion.

Flexible Logic allows advanced users to get unprecedented level of configurability for custom outputs and engine control. rusEfi supports up to 16 flexible outputs, each of these could be either an on/off or PWM signal. In case of a PWM signal the frequency is defined in the configuration and the duty cycle is dynamically controlled by the evaluated expression.

---

# RPN notation 

At the moment FSIO uses Reverse Polish Notation for technical reasons, so you would need to convert human-readable popular Infix notation to RPN using relevant rusEfi console features.


![img](overview/FSIO/FSIO_for_idle_target.png)

rusEFI console now has build-in decoder of RPN form, for example:

```decode_rpn "0 fsio_analog_input 20 > 0 10 if"```

Would return "Human form is "if((fsio_analog_input(0) > 20), 0, 10)"
"

and

```decode_rpn "0 fsio_input 20 > 0 10 if"```

It would show a filing to parse message with a list of some known functions.

---

##  Rev limit logic 
 
![img](Images/RevFSIO.png)  

FSIO setting 6 has been configured for an adjustable RPM limiter, this can be configured as shown above, the first number (2000) is the limit that will be active when the signal is on, the second (7000) is the standard limiter when the switch is deactivated. 

---

# See [legacy wiki](https://rusefi.com/wiki/index.php?title=Manual:Flexible_Logic) content below.  

Fuel pump is already using this mechanism - see https://github.com/rusefi/rusefi/blob/master/firmware/controllers/system_fsio.txt

Here are some commands to try:

eval "2 + 3"

Prints the result of "2 + 3"


eval "max (rpm, 100)"

Prints the result of "max(100, rpm)"


eval "if(1, 200, 100)"

Prints the result of "if(1, 200, 100)"


set_fsio_expression 1 "rpm > fsio_setting(4)"

Turn output #1 hi if rpm is greater than fsio setting #4


set_fsio_output_pin 1 pd11

Tells output #1 to use pin PD11


See https://github.com/rusefi/rusefi/blob/master/firmware/controllers/core/fsio_impl.cpp for list of available methods

---


## Contents  
1	[More Examples](##More-Examples)  
2	[FSIO parameters](##FSIO-parameters)  
3	[FSIO digital inputs](##FSIO-digital-inputs)  
4	[FSIO analog inputs](##FSIO-analog-inputs)  
5	[Case study #1: shift light](##Case-study-#1:-shift-light)  
6	[Case study #2: A/C compressor control](##Case-study-#2:-A/C-compressor-control)  
7	[Case study #3: digital inputs for extra devices](##Case-study-#3:-digital-inputs-for-extra-devices)  
8	[Case study #4: boost controller](##Case-study-#4:-boost-controller)  
9	[Case study #5: solenoid exhaust cam actuator](##Case-study-#5:-solenoid-exhaust-cam-actuator)  
10	[See aslo](##See-aslo)  
11	[Pin naming usability issue](##Pin-naming-usability-issue)  

---

## More Examples
set_fsio_output_frequency 1 100

Tells FSIO channel #1 to output 100Hz PWM


set_fsio_output_frequency 1 0


Now, let's assume we want duty cycle to be 10% if rpm is below 1000, 90% if rpm is above 5000, and have it grow linearly from 10% to 90% between 1000 rpm and 5000 rpm. The human-readable expression for that would be

min(0.9, max(0.1, (rpm - 1000) / 4000 * 0.8))


We can use

eval "min(0.9, max(0.1, (rpm - 1000) / 4000 * 0.8))"

to validate and then

set_fsio_expression 1 "min(0.9, max(0.1, (rpm - 1000) / 4000 * 0.8))"


Another version of the same logic would be


if (rpm < 1000, 0.1, if (rpm > 5000, 0.9, 0.1 + (rpm - 1000) / 4000 * 0.8))

TODO

---

## FSIO parameters
FSIO expressions could be customized using 16 user-defined 'settings' which are stored within the configuration. To change a setting from dev console your command is set_fsio_setting INDEX VAlUE

To access for example setting #3 your FSIO expression is

fsio_setting(3)

---

## FSIO digital inputs
These feature allows you to pull toggle switches state from your fsio expressions.

work in progress

---

## FSIO analog inputs
As of Aug 1, 2018 only one analog input is implemented:

rpn_eval "fsio_analog_input 0" or set_fsio_expression 0 "((rpm > fsio_setting(4) & (fsio_analog_input 0 < fsio_setting(5)) | rpm > fsio_setting(1) | (coolant > fsio_setting(2) > | (vbatt < fsio_setting(3)"

where input would be assigned via FSIO analog input #1

---

## Case study #1: shift light
We want to turn on a warning light if RPM is above 4500

In order to set an output, three commands have to be invoked, also user has to decide which FSIO unit between 1 and 16 to use. Separate commands are used to set duty cycle, output pin, and condition. All three commands referencing the same FSIO index. This is poor usability and one day someone would improve this somehow.

First we need to configure user output, let's use pin PE5 and index #3 for this example:

set_fsio_output_frequency 3 0

this would disable PWM on channel #3 and set this port to simple digital output mode

set_fsio_output_pin 3 PE5

Now we will set FSIO expression to control this output pin:

set_fsio_expression 3 "rpm > 4500"

here 3 is the index of the output pin

A configurable version of same would be

set_fsio_expression 3 "rpm > fsio_setting(3)"

set_fsio_setting 3 4500

---

## Case study #2: A/C compressor control
Say we want to use PE0 as A/C toggle button, and we want A/C compressor logic to be 'if (rpm > 1200 AND A/C button is depressed) then output 200Hz @ 80% duty cycle on PB1 else output nothing on PB1'.

First we need to configure A/C button input pin which is currently implemented as analog input (that's a temporary hack) - see engineConfiguration->acSwitchAdc

set_fsio_output_pin 3 PB1

Configure output #3 to use pin PB1

set_fsio_output_frequency 3 200

Configure output #3 to use 200Hz PWM

And finally set the expression:

'set_fsio_expression 3 "0 80 rpm 1200 > ac_on_switch AND IF"'

Which is RPN for if(rpm > 1200 AND ac_on_switch, 80, 0)

---

## Case study #3: digital inputs for extra devices
TODO


First we need to configure A/C digital input pin, we will use index 0:

set_fsio_input_pin 0 PE0

---

## Case study #4: boost controller
Solenoid-controlled boost controller would need variable duty cycle.

For example, let's use fsio table #3 to define the desired duty cycle:

![](Images/Fsio_table3.png)


Let's set PE11@300Hz as FSIO output #4

![](Images/Fsio_outputs.png)

And now the tricky part, let's set FSIO expression on that output using the following command

set_fsio_expression 4 "rpm map 3 fsio_table 100 /"

Do not forget writeconfig


fsioinfo could be used to monitor output value

![](Images/Fsioinfo.png) 


As for the magic expression, that's RPN for "fsio_table (3, rpm, map) / 100".

---

## Case study #5: solenoid exhaust cam actuator
Let's assume we want to turn on 200Hz solenoid at 80% duty cycle if RPM is above 6000.

Here is how this would look in Tuner Studio:

That's RPN notation for "(rpm > 6000) * 0.8"

See https://github.com/rusefi/rusefi/blob/master/firmware/controllers/system_fsio.txt see https://github.com/rusefi/rusefi/blob/master/firmware/controllers/system_fsio.h


![](Images/Fsio_TS.png)

---

## See aslo
set debug_mode 23 https://rusefi.com//wiki/index.php?title=Manual:Debug_fields

https://www.youtube.com/watch?v=nrIrtdn-Nc0

https://www.youtube.com/watch?v=eA4clVtklZ8

---

## Pin naming usability issue
We have a usability feature with microRusEfi where stm32 pin names are hidden from users. Unfortunately for FSIO these smt32 pin names are needed. Those are visible in https://github.com/rusefi/rusefi/blob/master/firmware/config/boards/microrusefi/mapping.yaml