# arduino 使用多个SPI设备 how to running multiple SPI device on arduino

- URL: https://wuming.si/blog/897/
- Author: Aaron
- Published: 2015-01-25
- Language: en
- Categories: Technology
- Originally published at: https://blog.wo.ai/archives/897

how to running PN532 and W5100 on same board

最近研究arduino开发板，尝试将NFC板(PN532)和网络扩展板(w5100)组合在一起，碰到个问题，这两块板子都是通过SPI总线和arduino通信，同时占用pin10,11,12,13三个口，其中10是片选信号SS。这两个设备始终无法同时工作，出现很多莫名其妙的问题。

[![154149rr5dubo9wbj9wlrw](https://wuming.si/images/2014/09/154149rr5dubo9wbj9wlrw-300x200.jpg)](https://wuming.si/images/2014/09/154149rr5dubo9wbj9wlrw.jpg)

比如我编译IDE自带的webserver程序，设置了ip地址为192.168.1.15，启动以后，ping 192.168.1.15可以通，但在串口接收到 ip地址为192.139.1.15,甚至是192.192.192.192,或者其他乱七八糟的地址。在PC上访问http://192.168.1.15无法打开。拔除NFC扩展板，web访问正常。然后开始漫长google之路。

参考链接

http://arduino.cc/en/Main/ArduinoEthernetShield

1.首先确认两个设备不能使用同一个SS pin，将nfc的nss针插到其他pin（貌似1，2，4，不能使用，4是SD卡的片选），我选择5，然后在arduino的setup里面增加

pinMode(5,OUTPUT);

digitalWrite(5,HIGH);

测试同时连接NFC和网络，只初始化网卡，webserver正常；如果同时初始化网卡和NFC，依旧无法访问webserver

参考链接

http://www.circuitsathome.com/mcu/running-multiple-slave-devices-on-arduino-spi-bus

2.继续google，发现两个设备的setBitOrder似乎不同，PN532是LSBFIRST，而网络是WSBFIRST，

找到原因后就简单了，只需要启动不同设备的时候，不仅仅设置SS，还要重新设置SPI的参数。

找到PN532.cpp的begin()，大约在43行，将

pn532_SPI.setDataMode(SPI_MODE0);  
pn532_SPI.setBitOrder(LSBFIRST);  
/*Set the SPI frequency to be one sixteenth of the  
frequency of the system clock*/  
pn532_SPI.setClockDivider(SPI_CLOCK_DIV16);

注释掉，然后在自己的程序里面分别写上

void enablePN() {  
digitalWrite(ETH_SS, HIGH);  
digitalWrite(NFC_SS, LOW);  
SPI.setDataMode(SPI_MODE0);  
SPI.setBitOrder(LSBFIRST);  
SPI.setClockDivider(SPI_CLOCK_DIV16);  
delay(10);  
}

void enableETH() {  
digitalWrite(ETH_SS, LOW);  
digitalWrite(NFC_SS, HIGH);  
SPI.setBitOrder(MSBFIRST);  
SPI.setClockDivider(SPI_CLOCK_DIV4);  
SPI.setDataMode(SPCR & SPI_MODE_MASK);  
SPCR &= ~(_BV(DORD));  
SPI.setClockDivider( SPCR & SPI_CLOCK_MASK);  
delay(10);  
}

需要网卡的时候enableETH，需要NFC的时候启用enablePN，完美解决。

完整测试代码如下：

> /* Web Server  
>  * A simple web server that shows the value of the analog input pins.  
>  */
> 
> #include <SPI.h>  
>  #include <Ethernet.h>  
>  #include <PN532.h>  
>  byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
> 
> byte ip[] = { 192, 168, 1, 15 };
> 
> EthernetServer server(80);  
>  #define NFC_DEMO_DEBUG 1  
>  #define PN532_CS 5  
>  PN532 nfc(PN532_CS);
> 
> void initNFC()  
>  {  
>  #ifdef NFC_DEMO_DEBUG  
>  Serial.println(“Begin start NFC!”);  
>  #endif  
>  nfc.begin();
> 
> uint32_t versiondata = nfc.getFirmwareVersion();  
>  if (! versiondata) {  
>  #ifdef NFC_DEMO_DEBUG  
>  Serial.print(“Didn’t find PN53x board”);  
>  #endif  
>  //while (1); // halt  
>  return;  
>  // skip NFC, continue other step without NFC  
>  }  
>  #ifdef NFC_DEMO_DEBUG  
>  // Got ok data, print it out!  
>  Serial.print(“Found chip PN5”);  
>  Serial.println((versiondata>>24) & 0xFF, HEX);  
>  Serial.print(“Firmware ver. “);  
>  Serial.print((versiondata>>16) & 0xFF, DEC);  
>  Serial.print(‘.’);  
>  Serial.println((versiondata>>8) & 0xFF, DEC);  
>  Serial.print(“Supports “);  
>  Serial.println(versiondata & 0xFF, HEX);  
>  #endif  
>  // configure board to read RFID tags and cards  
>  nfc.SAMConfig();  
>  }  
>  void NFCReading()  
>  {  
>  uint32_t id;  
>  // look for MiFare type cards  
>  id = nfc.readPassiveTargetID(PN532_MIFARE_ISO14443A);
> 
> if (id != 0) {  
>  #ifdef NFC_DEMO_DEBUG  
>  Serial.print(“Read card #”);  
>  Serial.println(id);  
>  #endif  
>  }  
>  }  
>  void WebPrint(EthernetClient client)  
>  {
> 
> if (client) {  
>  // an http request ends with a blank line  
>  boolean current_line_is_blank = true;  
>  while (client.connected()) {  
>  if (client.available()) {  
>  char c = client.read();  
>  // if we’ve gotten to the end of the line (received a newline  
>  // character) and the line is blank, the http request has ended,  
>  // so we can send a reply  
>  if (c == ‘\n’ && current_line_is_blank) {  
>  // send a standard http response header  
>  client.println(“HTTP/1.1 200 OK”);  
>  client.println(“Content-Type: text/html”);  
>  client.println();
> 
> // output the value of each analog input pin  
>  client.print(“welcome to tinyos”);  
>  client.println(“<br />”);  
>  client.print(“//*************************************”);  
>  client.println(“<br />”);  
>  client.print(“www.tinyos.net.cn”);  
>  client.println(“<br />”);  
>  client.print(“//*************************************”);  
>  client.println(“<br />”);  
>  for (int i = 0; i < 6; i++) {  
>  client.print(“analog input “);  
>  client.print(i);  
>  client.print(” is “);  
>  client.print(analogRead(i));  
>  client.println(“<br />”);  
>  }  
>  break;  
>  }  
>  if (c == ‘\n’) {  
>  // we’re starting a new line  
>  current_line_is_blank = true;  
>  } else if (c != ‘\r’) {  
>  // we’ve gotten a character on the current line  
>  current_line_is_blank = false;  
>  }  
>  }  
>  }  
>  client.stop();  
>  }  
>  }  
>  #define ETH_SS 10  
>  #define NFC_SS 5  
>  void enablePN() {  
>  digitalWrite(ETH_SS, HIGH);  
>  digitalWrite(NFC_SS, LOW);  
>  SPI.setDataMode(SPI_MODE0);  
>  SPI.setBitOrder(LSBFIRST);  
>  SPI.setClockDivider(SPI_CLOCK_DIV16);  
>  delay(10);  
>  }
> 
> void enableETH() {  
>  digitalWrite(ETH_SS, LOW);  
>  digitalWrite(NFC_SS, HIGH);  
>  SPI.setBitOrder(MSBFIRST);  
>  SPI.setClockDivider(SPI_CLOCK_DIV4);  
>  SPI.setDataMode(SPCR & SPI_MODE_MASK);  
>  SPCR &= ~(_BV(DORD));  
>  SPI.setClockDivider( SPCR & SPI_CLOCK_MASK);  
>  delay(10);  
>  }  
>  void setup()  
>  {  
>  Serial.begin(9600);  
>  pinMode(10, OUTPUT);  
>  pinMode(5, OUTPUT);  
>  pinMode(4, OUTPUT);  
>  enableETH();  
>  Ethernet.begin(mac, ip);  
>  server.begin();  
>  Serial.print(“server is at “);  
>  Serial.println(Ethernet.localIP());  
>  enablePN();  
>  initNFC();  
>  //digitalWrite(5,HIGH);  
>  //digitalWrite(10,LOW);  
>  }
> 
> void loop()  
>  {  
>  // pinMode(4,HIGH);  
>  //digitalWrite(5,HIGH);  
>  //digitalWrite(10,LOW);  
>  enableETH();  
>  EthernetClient client = server.available();  
>  WebPrint(client);  
>  enablePN();  
>  //delay(100);  
>  //digitalWrite(5,HIGH);  
>  //digitalWrite(10,LOW);  
>  NFCReading();  
>  //delay(100);  
>  }

后记：通过这种方式实现了网络、NFC、SD卡读写的协同工作。