mruby-bin-mirb-hostbased

mruby-bin-mirb-hostbased is mrbgem which allows hostbased irb with mruby.

Compiled executable "mirb-hostbased" is simular to mirb, but mirb-hostbased works with target board via serial communication.

Demo

http://www.youtube.com/watch?v=e8gTTSdxlPU

http://www.youtube.com/watch?v=zNeGxjQD1Y0

How it works

As name "hostbased" implies, mirb-hostbased does not send user input directly to target board, rather, it compiles user input into bytecode on host machine, then send bytecode via serial.

Target boards should handle received bytecode, then send result back to host. Sample sketch for chipKIT Max32 (and maybe for Arduino Due) is in samples/target.

Build

Host side:

Add below line in host Build setting of build_config.rb in mruby's source tree.

conf.gem :github => 'kyab/mruby-bin-mirb-hostbased', :branch => 'master'

Target side:

If your board is Arduino compatible, compile and upload sample sketch file in samples/target by your IDE(Arduino IDE, MPIDE,etc). I also recommend you to use my mruby-arduino.

conf.gem :github => "kyab/mruby-arduino.git", :branch => "master"

Usage

mirb-hostbased -p <port>

<port> is serial(or USB Serial) port that target connected.

Example:

 mirb-hostbased -p /dev/cu.usbserial-A600CKP6

Once prompt ">" is displayed, your target is ready. Enter any ruby code like mirb.

mirb-hostbased -p /dev/cu.usbserial-A600CKP6 
mirb-hostbased - Hostbased Interactive mruby Shell
  waiting for target on /dev/cu.usbserial-A600CKP6...
(taget):TOTAL_ALLOCATED : 83297
target is ready.
> 1+1
 => 2
> "mruby".upcase.reverse
 => YBURM
> exit

Note: you should use /dev/cu.. /dev/tty. may not work.

Loading file

You can use #load(or #file) special command to read *.rb files.

test.rb

def square_add(a,b)
  a*a + b*b
end
puts "test.rb loaded into target"

mirb-hostbased:

> #load /path/to/test.rb
test.rb loaded into target
 => nil
> square_add(2,3)
 => 25

Reconnect (without reset)

You can reconnect to serial(usb-serial) if your device is self-powered. With #reconnect command or --noreset option, mirb-hostbased simply reopen serial port.

> n=100
 => 100 
> #reconnect
reconnecting to /dev/cu.usbserial-A600CKP6...
> n
 => 100

or

> $n=100
 => 100 
> exit
mirb-hostbased --noreset -p /dev/cu.usbserial-A600CKP6
> $n
 => 100

restriction: With --noreset option, you cannot reuse local variable in previous mirb-hostbased session. This is because mirb-hostbased can not restore previous context.

###For Arduino boards: Usually Arduino boards automatically reset when USB is (re)connected even self-powered from external power source. So to use #reconnect command or --noreset option, you have to disable auto-reset temporarily. I recommend to use capacitor hack introduced bellow. http://electronics.stackexchange.com/questions/24743/arduino-resetting-while-reconnecting-the-serial-terminal.

Your sessions would be like.

(Arduino is default and self-powered: auto-reset enabled.)
mirb-hostbased -p /dev/cu.usbserial-A600CKP6
> def foo
*   puts "foo"
* end
 => nil
> n = 99
 => 99
(Disconnect USB.)
(Have fun with target.)
(Connect capacitor between RESET and GND on board. auto-reset disabled.)
(Reconnect USB)
> #reconnect
> foo
foo
 => nil
> n
 => 99

#load/#file command and #reconnect option provide you rapid try-and-test cycle.

Related articles

##My blog post: Hostbased irb Chap.1(Japanese): http://d.hatena.ne.jp/kyab/20130621

Hostbased irb Chap.2(Japanese): http://d.hatena.ne.jp/kyab/20130625

How to compile mruby for chipKITMax32(Japanese): http://d.hatena.ne.jp/kyab/20130201

##Arduino Due mirb(full compiler on board) Interactive Arduino Shell - mruby.sh http://blog.mruby.sh/201305201003.html