通信接口

Firmat详细解析

字号+ 作者:duino123.com 来源:未知 2016-12-16 16:13 我要评论( )

一、简介 Firmata是一个PC与MCU通讯的一个常用协议。其遵旨是能与任何主机PC软件包兼容。到目前为止,已经得到不少语言的支持,这样可方便地将对协议的支持加入软件系统中。Firmata起初是针对于PC与Arduino通讯的固件(Firmware),其目标是让开发者可以通过PC

一、简介

Firmata是一个PC与MCU通讯的一个常用协议。其遵旨是能与任何主机PC软件包兼容。到目前为止,已经得到不少语言的支持,这样可方便地将对协议的支持加入软件系统中。Firmata起初是针对于PC与Arduino通讯的固件(Firmware),其目标是让开发者可以通过PC软件完全地控件Arduino。

image

 

二、Firmata协议详解

 

I/O支持

  • 超过16路模拟通道
  • 超过128(16 * 8-bit ports)路数字通道

 

消息类型

/* This protocol uses the MIDI message format, but does not use the whole
 * protocol.  Most of the command mappings here will not be directly usable in
 * terms of MIDI controllers and synths.  It should co-exist with MIDI without
 * trouble and can be parsed by standard MIDI interpreters.  Just some of the
 * message data is used differently.
 *
 * MIDI format: http://www.harmony-central.com/MIDI/Doc/table1.html
 * 
 *                              MIDI       
 * type                command  channel    first byte            second byte 
 *----------------------------------------------------------------------------
 * analog I/O message    0xE0   pin #      LSB(bits 0-6)         MSB(bits 7-13)
 * digital I/O message   0x90   port       LSB(bits 0-6)         MSB(bits 7-13)
 * report analog pin     0xC0   pin #      disable/enable(0/1)   - n/a -
 * report digital port   0xD0   port       disable/enable(0/1)   - n/a -
 *
 * sysex start           0xF0   
 * set pin mode(I/O)     0xF4              pin # (0-127)         pin state(0=in)
 * sysex end             0xF7   
 * protocol version      0xF9              major version         minor version
 * system reset          0xFF
 *
 */
/* SysEx-based commands (0x00-0x7F) are used for an extended command set.
 *
 * type                command  first byte       second byte      ...
 *-----------------------------------------------------------------------------
 * string                0x71   char *string ...
 * firmware name/version 0x79   major version   minor version     char *name...
 */ 

该协议使用了MIDI消息格式,但并非MIDI消息格式的完整实现,Firmata中大多数命令不能直接按MIDI规定的的术语来使用。
但可与MIDI兼容并可被任何标准MIDI解释器兼容。仅有部分消息数据的使用是不同的。

MIDI消息格式

类型

命令

MIDI通道

第一字节

第二字节

模拟IO消息 0xE0 引脚# 低字节(0-6) 高字节(7-13)
数字IO消息 0x90 端口 低字节(0-6) 高字节(7-13)
报告模拟引脚 0xC0 引脚# 禁止/使能(0/1)  
报告数字端口 0xD0 端口 禁止/使能(0/1)  
         
sysex命令起始 0xF0      
引脚模式设置 0xF4   引脚# 引脚状态(0=输入)
sysex命令停止 0xF7      
协议版本 0xF9   主版本 次版本
系统重启 0xFF      
         
基于sysex的命令        
字符串 0x71 char *string ...    
固件版本 0x79 主版本 次版本 char *name...

 

数据消息详解

/* two byte digital data format    两字节数字数据格式
 * 0  digital data, 0x90-0x9F, (MIDI NoteOn, but different data format)    数字数据,0x90-0x9F
 * 1  digital pins 0-6 bitmask    数字引脚0-6位标志掩码
 * 2  digital pins 7-13 bitmask    数字引脚7-13位标志掩码 
 */
/* analog 14-bit data format    14位模拟数据格式
 * 0  analog pin, 0xE0-0xEF, (MIDI Pitch Wheel)    模拟引脚,0xE0-0xEF
 * 1  analog least significant 7 bits    模拟最低有效位7位
 * 2  analog most significant 7 bits     模拟最高有效位7位
 */
/* version report format
 * -------------------------------------------------
 * 0  version report header (0xF9) (MIDI Undefined)
 * 1  major version (0-127)
 * 2  minor version (0-127)
 */

 

 

控制消息详解

/* set pin mode设置引脚模式
 * 1  set digital pin mode (0xF4) (MIDI Undefined)
 * 2  pin number (0-127)
 * 3  state (INPUT/OUTPUT/ANALOG/PWM/SERVO, 0/1/2/3/4)
 */
/* toggle analogIn reporting by pin
 * 0  toggle digitalIn reporting (0xC0-0xCF) (MIDI Program Change)
 * 1  disable(0)/enable(non-zero) 
 */
/* toggle digital port reporting by port
 * 0  toggle digital port reporting (0xD0-0xDF) (MIDI Aftertouch)
 * 1  disable(0)/enable(non-zero) 
 */
/* request version report
 * 0  request version report (0xF9) (MIDI Undefined)
 */

 

 

Sysex消息格式

The idea for SysEx is to have a second command space using the first byte after the SysEx Start byte. The key difference is that the data can be of any size, rather than just one or two bytes for standard MIDI messages.

SysEX的思想是在继SysEx起始字节之后,具备包含第二消息的能力。与非SysEX的命令相比,其最大的优点在于数据的大小可以任意定义,而不是像标准MIDI格式那样的仅仅一个或二个字节

/* Generic Sysex Message
 * 0     START_SYSEX (0xF0)
 * 1     sysex command (0x00-0x7F)
 * x     between 0 and MAX_DATA_BYTES 7-bit bytes of arbitrary data
 * last  END_SYSEX (0xF7)
 */

 

Query Firmware Name and Version

The firmware name to be reported should be exactly the same as the name of the Arduino file, minus the .pde. So for Standard_Firmata.pde, the firmware name is: Standard_Firmata.

/* Query Firmware Name and Version
 * 0  START_SYSEX (0xF0)
 * 1  queryFirmware (0x79)
 * 2  END_SYSEX (0xF7)
 */
/* Receive Firmware Name and Version (after query)
 * 0  START_SYSEX (0xF0)
 * 1  queryFirmware (0x79)
 * 2  major version (0-127)
 * 3  minor version (0-127)
 * 4  first 7-bits of firmware name
 * 5  second 7-bits of firmware name
 * x  ...for as many bytes as it needs)
 * 6  END_SYSEX (0xF7)
 */

 

I2C
/* I2C read/write request
 * -------------------------------
 * 0  START_SYSEX (0xF0) (MIDI System Exclusive)
 * 1  I2C_REQUEST (0x76)
 * 2  slave address (LSB)
 * 3  slave address (MSB) + read/write and address mode bits
      {7: always 0} + {6: reserved} + {5: address mode, 1 means 10-bit mode} +
      {4-3: read/write, 00 => write, 01 => read once, 10 => read continuously, 11 => stop reading} +
      {2-0: slave address MSB in 10-bit mode, not used in 7-bit mode}
 * 4  data 0 (LSB)
 * 5  data 0 (MSB)
 * 6  data 1 (LSB)
 * 7  data 1 (MSB)
 * ...
 * n  END_SYSEX (0xF7)
 */
/* I2C reply
 * -------------------------------
 * 0  START_SYSEX (0xF0) (MIDI System Exclusive)
 * 1  I2C_REPLY (0x77)
 * 2  slave address (LSB)
 * 3  slave address (MSB)
 * 4  register (LSB)
 * 5  register (MSB)
 * 6  data 0 LSB
 * 7  data 0 MSB
 * ...
 * n  END_SYSEX (0xF7)
 */
/* I2C config
 * -------------------------------
 * 0  START_SYSEX (0xF0) (MIDI System Exclusive)
 * 1  I2C_CONFIG (0x78)
 * 2  Power pin settings (0:off or 1:on)
 * 3  Delay in microseconds (LSB)
 * 4  Delay in microseconds (MSB)
 * ... user defined for special cases, etc
 * n  END_SYSEX (0xF7)
 */

 

Sampling Interval
/* Set sampling interval
 * -------------------------------
 * 0  START_SYSEX (0xF0) (MIDI System Exclusive)
 * 1  SAMPLING_INTERVAL (0x7A)
 * 2  sampling interval on the millisecond time scale (LSB)
 * 3  sampling interval on the millisecond time scale (MSB)
 * 4  END_SYSEX (0xF7)
 */

 

Servos

This is the current proposal for adding Servo support based on feedback from Bjoern Hartmann, Shigeru Kobayashi, and Erik Sjodin. The core idea is to just add a "config" message, then use the SET_PIN_MODE message to attach/detach Servo support to a pin. This is how hardware PWM is currently handled. This would save space in the protocol by reusing the SET_PIN_MODE message, but the host software implementation could have a different interface, e.g. Arduino's attach() anddetach().

minPulse, maxPulse, and angle are all 14-bit unsigned integers. Angle is in degrees. The SERVO_CONFIG can be sent at any time to change the settings.

/* servo config
 * --------------------
 * 0  START_SYSEX (0xF0)
 * 1  SERVO_CONFIG (0x70)
 * 2  pin number (0-127)
 * 3  minPulse LSB (0-6)
 * 4  minPulse MSB (7-13)
 * 5  maxPulse LSB (0-6)
 * 6  maxPulse MSB (7-13)
 * 7  angle LSB (0-6)
 * 8  angle MSB (7-13)
 * 9  END_SYSEX (0xF7)
 */

This is just the standard SET_PIN_MODE message:

/* set digital pin mode
 * --------------------
 * 1  set digital pin mode (0xF4) (MIDI Undefined)
 * 2  pin number (0-127)
 * 3  state (INPUT/OUTPUT/ANALOG/PWM/SERVO, 0/1/2/3/4)
 */

Then the normal ANALOG_MESSAGE data format is used to send data.

/* write to servo, servo write is performed if the pins mode is SERVO
 * ------------------------------
 * 0  ANALOG_MESSAGE (0xE0-0xEF)
 * 1  value lsb
 * 2  value msb
 */

3、Arduino <> Firmata <> Visual Basic .NET

FirmataVB是一个基于.NET的用户自定义类库,使用Firmata 2.0协议发送消息、接收数据。

在使用Firmata之前,我曾经用Processing来控制Arduino,找到了其中的Arduino.java文件,并改版,写成了Arduino.cs,不过,当时没有想的像FirmataVB的作者这么周全,做成控件,方便使用者调用,也没有完善的文档,仅是在实验室里流传使用。Arduino.cs的源码,见GasSensorArray_Ver0.8,这个工程包含了Arduino.cs


	Arduino.cs

FirmataVB控件的用法与其他控件一样,都有两种用法:

一、加入ToolBox,拖入界面设计中

二、在代码中,手动加入引用,并在工程的Reference中,加入FirmataVB.dll


using Firmata.FirmataVB

另外,在FirmataVB中,还加入了对数字引脚控制,模拟引脚控制的UI控件,如下图所示:

image image

 

 image image

在使用这两个UI控件时,当然只能使用前述的第一种方式,也就是引入ToolBox后,将其拖入界面设计表单中。这两个控件并不向Arduino发送任何命令,只是一些参数的设置,如端口号等!

4. FirmataVB的用法

FirmataVB的用法很简单,先看一下FirmataVB的库结构:

image

下图为FirmataVB中的方法,每个方法的名称已经可以大致说明该方法的功能,在此只举常用的几个进行说明。

  1. 1.
     public void AnalogPinReport(int pin, int mode)
    该方法设置某模拟通道开启或开闭。如:
    private void analogx_AnalogOnOff_Changed(int PinNumber, int OnOff)
    {
        arduino.AnalogPinReport(PinNumber, OnOff);//analogx是一个AnalogControl控件对象,arduino 是一个Firmata对象
    }

image

下图是FirmataVB所支持的Arduino板子的类型

image

5、参考

1. Firmata官方网站

2.FirmataVB

 

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