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。
/* 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
/* 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) */
/* 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) */
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) */
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 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) */
/* 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) */
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() and detach().
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 */
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:
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！
FirmataVB的用法很简单，先看一下FirmataVB的库结构：
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。
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 }
下图是FirmataVB所支持的Arduino板子的类型
1. Firmata官方网站
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