事實上 GrovePi 的『應用軟體界面』 API
GrovePi/Software/Python/grovepi.py
# 【所需程式庫】 44 import smbus 45 import time 46 import math 47 import RPi.GPIO as GPIO 48 import struct 49 import sys 50 # 【除錯模式】 51 debug =0 52 # 【派生版本】 53 if sys.version_info<(3,0): 54 p_version=2 55 else: 56 p_version=3 57 # 【 GPIO 版本/樹莓派版本】 58 rev = GPIO.RPI_REVISION 59 if rev == 2 or rev == 3: 60 bus = smbus.SMBus(1) 61 else: 62 bus = smbus.SMBus(0) 63 # 【 Arduino I2C 地址】 64 # I2C Address of Arduino 65 address = 0x04 # 【 Arduino 提供之命令】 67 # Command Format # 【 主從 I2C 通訊】 158 # Function declarations of the various functions used for encoding and sending 159 # data from RPi to Arduino # 【應用程式界面 API 】 190 # Arduino Digital Read 191 def digitalRead(pin): 192 write_i2c_block(address, dRead_cmd + [pin, unused, unused]) 193 time.sleep(.1) 194 n = read_i2c_byte(address) 195 return n 196 197 # Arduino Digital Write 198 def digitalWrite(pin, value): 199 write_i2c_block(address, dWrite_cmd + [pin, value, unused]) 200 return 1 201 202 203 # Setting Up Pin mode on Arduino 204 def pinMode(pin, mode): 205 if mode == "OUTPUT": 206 write_i2c_block(address, pMode_cmd + [pin, 1, unused]) 207 elif mode == "INPUT": 208 write_i2c_block(address, pMode_cmd + [pin, 0, unused]) 209 return 1 210 211 212 # Read analog value from Pin 213 def analogRead(pin): 214 bus.write_i2c_block_data(address, 1, aRead_cmd + [pin, unused, unused]) 215 time.sleep(.1) 216 bus.read_byte(address) 217 number = bus.read_i2c_block_data(address, 1) 218 time.sleep(.1) 219 return number[1] * 256 + number[2]
，與之『韌體』
GrovePi/Firmware/Source/v1.2/grove_pi_v1_2_5/grove_pi_v1_2_5.ino
# 【對應的 Arduino 之指令】
101 //Digital Read
102 else if(cmd[0]==1)
103 val=digitalRead(cmd[1]);
104
105 //Digital Write
106 else if(cmd[0]==2)
107 digitalWrite(cmd[1],cmd[2]);
108
109 //Analog Read
110 else if(cmd[0]==3)
111 {
112 aRead=analogRead(cmd[1]);
113 b[1]=aRead/256;
114 b[2]=aRead%256;
115 }
116
117 //Set up Analog Write
118 else if(cmd[0]==4)
119 analogWrite(cmd[1],cmd[2]);
120
121 //Set up pinMode
122 else if(cmd[0]==5)
123 pinMode(cmd[1],cmd[2]);
，都是平鋪直敘，沒有太多疑惑之處。但想深入『解讀』者，或許需要先了解
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Parent directory | |
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busses/ | |
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muxes/ | |
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dev-interface | 8885 bytes |
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fault-codes | 5042 bytes |
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functionality | 6119 bytes |
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i2c-protocol | 3041 bytes |
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i2c-stub | 2323 bytes |
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instantiating-devices | 9755 bytes |
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old-module-parameters | 1899 bytes |
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slave-eeprom-backend | 474 bytes |
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slave-interface | 7087 bytes |
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smbus-protocol | 9176 bytes |
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summary | 1920 bytes |
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ten-bit-addresses | 1260 bytes |
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upgrading-clients | 6954 bytes |
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writing-clients | 15331 bytes |
相關文件。此處僅列出『 I2C 』和『 SMBus 』摘要︰
Linux/Documentation/i2c/summary
I2C and SMBus
=============
I2C (pronounce: I squared C) is a protocol developed by Philips. It is a
slow two-wire protocol (variable speed, up to 400 kHz), with a high speed extension (3.4 MHz). It provides an inexpensive bus for connecting many types of devices with infrequent or low bandwidth communications needs. I2C is widely used with embedded systems. Some systems use variants that don’t meet branding requirements, and so are not advertised as being I2C.
SMBus (System Management Bus) is based on the I2C protocol, and is mostly a subset of I2C protocols and signaling. Many I2C devices will work on an SMBus, but some SMBus protocols add semantics beyond what is required to achieve I2C branding. Modern PC mainboards rely on SMBus. The most common devices connected through SMBus are RAM modules configured using I2C EEPROMs,
and hardware monitoring chips.
Because the SMBus is mostly a subset of the generalized I2C bus, we can use its protocols on many I2C systems. However, there are systems that don’t meet both SMBus and I2C electrical constraints; and others which can’t implement all the common SMBus protocol semantics or messages.
Terminology
===========
When we talk about I2C, we use the following terms:
Bus -> Algorithm
Adapter
Device -> Driver
Client
An Algorithm driver contains general code that can be used for a whole class of I2C adapters. Each specific adapter driver either depends on one algorithm driver, or includes its own implementation.
A Driver driver (yes, this sounds ridiculous, sorry) contains the general code to access some type of device. Each detected device gets its own data in the Client structure. Usually, Driver and Client are more closely integrated than Algorithm and Adapter.
For a given configuration, you will need a driver for your I2C bus, and
drivers for your I2C devices (usually one driver for each device).
至於『 python-smbus 』的說明簡介，也許讀者可以參考
。然而為何如此的規劃『架構』？？作者亦莫宰羊的耶！！