如何在Raspberry Pi運行Arduino程式

Jan Gromes

Published by Jan Gromes at 2020.07.03

高級範例：SPI和I2C

顯然，LED閃爍和控制台輸出等功能可以完成許多不錯的專案，但是我認為，如果添加一些更高級的功能，比如I2C和SPI，我們就可以做更多事情。RasPiArduino框架同樣支援這些功能，所以我們可以用I2C匯流排將不同的感測器連至Raspberry；或者讓Raspberry透過SPI匯流排與各通信模組進行通信。對於I2C器件，我使用的是羅姆感測器評估套件中的BH1745NUC顏色感測器；對於SPI，我用的是SX1278 LoRa模組。這兩者的運行電壓邏輯都是3.3V，因此只需幾根線纜就可以將它們與Raspberry連接起來，非常簡單。

圖12 本例的接線示意圖

多虧了LoRaLib和RohmMultiSensor程式館，系統代碼也非常簡單！基本上就是LoRaLib程式館中的接收器範例代碼加上RohmMultiSensor程式館中的BH1745NUC範例代碼。

// define the sensor we will use
#define INCLUDE_BH1745NUC

// include the libraries
#include <RohmMultiSensor.h>
#include <LoRaLib.h>

// instantiate the sensor's class
BH1745NUC sensorColor;

// SX1278 digital I/O pin 0
int dio0 = 17;

// SX1278 digital I/O pin 1
int dio1 = 27;

// SX1278 SPI slave select pin
int nss = 22;

// create LoRa class instance
LoRa lora(CH_SX1278, nss, BW_125_00_KHZ, SF_9, CR_4_7, dio0, dio1);

// create empty instance of Packet class
Packet pack;

void setup() {
// start I2C communication
Wire.begin();

// initialize LoRa
uint8_t state = lora.begin();
if(state == ERR_NONE) {
Console.println("[SX1278]\tInitialization done.");
} else {
Console.print("[SX1278]\tInitialization failed, code 0x");
Console.println(state, HEX);
while(true);
}

// initialize the sensor with default settings
state = sensorColor.init();
if(state == 0) {
Console.println("[BH1745]\tInitialization done.");
} else {
Console.print("[BH1745]\tInitialization failed, code 0x");
Console.println(state, HEX);
while(true);
}

Console.println("-------------------------------------------------------------------");
}

void loop() {
Console.print("[SX1278]\tWaiting for incoming transmission ... ");

// wait for single packet
uint8_t state = lora.receive(pack);

if(state == ERR_NONE) {
// packet was suceesfully received
Console.println("success!");

// print the data of the packet
Console.print("[SX1278]\tData:\t\t");
Console.println(pack.data);

} else if(state == ERR_RX_TIMEOUT) {
// timeout occured while waiting for a packet
Console.println("timeout!");

} else if(state == ERR_CRC_MISMATCH) {
// packet was received, but is malformed
Console.println("CRC error!");

}

Console.println("-------------------------------------------------------------------");

Console.print("[BH1745]\tColor Values (R-G-B-C):\t");

// measure the sensor values
sensorColor.measure();

// print the values to the console
Console.print(sensorColor.red);
Console.print('\t');
Console.print(sensorColor.green);
Console.print('\t');
Console.print(sensorColor.blue);
Console.print('\t');
Console.println(sensorColor.clear);

Console.println("-------------------------------------------------------------------");
}

// define the sensor we will use

#define INCLUDE_BH1745NUC

// include the libraries

#include <RohmMultiSensor.h>

#include <LoRaLib.h>

// instantiate the sensor's class

BH1745NUC sensorColor;

// SX1278 digital I/O pin 0

int dio0 = 17;

// SX1278 digital I/O pin 1

int dio1 = 27;

// SX1278 SPI slave select pin

int nss = 22;

// create LoRa class instance

LoRa lora(CH_SX1278, nss, BW_125_00_KHZ, SF_9, CR_4_7, dio0, dio1);

// create empty instance of Packet class

Packet pack;

void setup() {

// start I2C communication

Wire.begin();

// initialize LoRa

uint8_t state = lora.begin();

if(state == ERR_NONE) {

Console.println("[SX1278]\tInitialization done.");

} else {

Console.print("[SX1278]\tInitialization failed, code 0x");

Console.println(state, HEX);

while(true);

}

// initialize the sensor with default settings

state = sensorColor.init();

if(state == 0) {

Console.println("[BH1745]\tInitialization done.");

} else {

Console.print("[BH1745]\tInitialization failed, code 0x");

Console.println(state, HEX);

while(true);

}

Console.println("-------------------------------------------------------------------");

}

void loop() {

Console.print("[SX1278]\tWaiting for incoming transmission ... ");

// wait for single packet

uint8_t state = lora.receive(pack);

if(state == ERR_NONE) {

// packet was suceesfully received

Console.println("success!");

// print the data of the packet

Console.print("[SX1278]\tData:\t\t");

Console.println(pack.data);

} else if(state == ERR_RX_TIMEOUT) {

// timeout occured while waiting for a packet

Console.println("timeout!");

} else if(state == ERR_CRC_MISMATCH) {

// packet was received, but is malformed

Console.println("CRC error!");

}

Console.println("-------------------------------------------------------------------");

Console.print("[BH1745]\tColor Values (R-G-B-C):\t");

// measure the sensor values

sensorColor.measure();

// print the values to the console

Console.print(sensorColor.red);

Console.print('\t');

Console.print(sensorColor.green);

Console.print('\t');

Console.print(sensorColor.blue);

Console.print('\t');

Console.println(sensorColor.clear);

Console.println("-------------------------------------------------------------------");

}

電路實物如下圖所示。雖然不漂亮，但是很實用。

圖13 已連接SX1278無線模組和BH1274NUC顏色感測器的Raspberry Pi

在此範例中，所有重要資訊都被列印到Raspberry控制台。我們可以看到，SX1278成功接收到了包含字串“Hello Raspberry！”的資料包（從Arduino透過LoRenz研發板發送），而且顏色感測器測量的值也是正確的！

圖14 Raspberry Pi控制台輸出

結論

那麼結論是：我們可以將Raspberry Pi當作Arduino研發板進行程式設計嗎？絕對可以！但是，這兩種系統都有優缺點。Raspberry的處理速度更快，Arduino功耗更低；Raspberry具有內建的HDMI和乙太網埠，而Arduino具有內建的模數轉換器。其他對比不再一一列舉。但是，這歸根結底是因為Arduino和Raspberry的應用場景不同。比如，如果您需要構建基於電池的感測器監控系統，請選Arduino。如果您需要透過機器學習來處理相機圖片，請選Raspberry Pi。總之，我們必須根據系統要處理的任務類型選擇適當元件，反之則不行。