尝试将数据写入串口时，我遇到了一个奇怪的问题。我在NUC7i7DNBE上运行Ubuntu 16.04，我正在尝试与Arduino UNO建立串行连接。我正在使用的串行API在这里找到：http://docs.ros.org/kinetic/api/serial/html/classserial_1_1Serial.html
我写了一个简单的程序，打开串口“ttyACM0”与arduino进行通信。我在另一台运行Ubuntu 16.04的计算机上测试了这个代码，一切正常，我必须设置的唯一权限是将用户添加到拨出组。
但是，在NUC上，我已将用户添加到拨出组。这允许程序从Arduino读取，但它仍然没有写入Arduino。 Arduino IDE会写入Arduino就好了，但我的程序不会。
我假设我在Ubuntu中遇到串行写权限问题。
我采取的步骤：
SUBSYSTEMS=="tty", GROUP="dialout", MODE="0666"
sudo chown root:root /etc/udev/rules.d/50-AVCusb.rules
sudo chmod 0644 /etc/udev/rules.d/50-AVCusb.rules
udevadm control --reload-rules
我跟踪了在堆栈交换中找到的一些信息，以达到这一点：https://unix.stackexchange.com/questions/111593/allow-non-root-user-to-read-write-dev-files
我一般没有处理过很多Ubuntu权限或端口，请帮我找到并上传您可能需要的任何其他信息，以帮助我解决这个问题。
NUC代码：
#include <ros/ros.h>
#include <serial/serial.h>
using namespace serial;
Serial ser;
static const uint8_t MOTOR_ID = 0;
void writeMotor(uint8_t byte)
{
size_t size = 4;
uint8_t buffer[size];
buffer[0] = 'G'; //PID
buffer[1] = 'O';
buffer[2] = MOTOR_ID; //address
buffer[3] = byte; //data byte
ser.write(buffer, size);
}
int main() {
ros::init(argc, argv, "servo_esc_driver");
std::string port = "/dev/ttyACM0";
Timeout timeout = Timeout(0, 0, 0, 0, 0);
bytesize_t bytesize = eightbits;
parity_t parity = parity_none;
stopbits_t stopbits = stopbits_one;
flowcontrol_t flowcontrol = flowcontrol_none;
try{
ser.setPort(port);
ser.setBaudrate(115200);
ser.setTimeout(timeout);
ser.setBytesize(bytesize);
ser.setParity(parity);
ser.setStopbits(stopbits);
ser.setFlowcontrol(flowcontrol);
ser.open();
}
catch (SerialException e) {
ROS_FATAL_NAMED("Failed to connect to the Arduino UNO, %s.", e.what());
ros::shutdown();
return 0;
}
uint8_t byte = 90;
writeMotor(byte);
}
Arduino完整代码
#include <Servo.h>
const byte N = 2;
//Servo esc;
//Servo servo;
Servo servo[N];
//int escPos = 90;
//int servoPos = 90;
int pos[N];
static const byte ESC_PIN = 7;
static const byte SERVO_PIN = 8;
static const byte RPM_FEEDBACK_PIN = 0; //interrpt 0, pin 2
static const byte SERVO_FEEDBACK_PIN = A0;
//const float MUL = 0.7058823529; //180/255
unsigned long lastTime_servoFeedback = 0;
static const byte MOTOR_ID = 0; //ID for differentiating data received and sent over serial connections
static const byte SERVO_ID = 1;
//added for motor data timeout safety feature
static const unsigned long MOTOR_DATA_TIMEOUT = 200; //4 x 50 ms (50 ms time period expected)
static unsigned long lastTimeMotorData = 0;
static const byte NEUTRAL = 90;
unsigned long last_rpm_pulse_update_ms = 0; //used for detecting a stopped car, and rejecting old data when writing to the serial port
unsigned long last_rpm_pulse_time_us = 0;//keeps track of rpms by comparing to system timer
static const long REV_PERIOD_MAX_US = 100000; //in us
unsigned long rev_period = REV_PERIOD_MAX_US; //100 ms is considered too long to be in motion
boolean forward = true;
/*Scratch that, I want these parameters set in ROS:
static const float wheel_radius = 0.05 // meters
static const float revs_to_mps_MUL = //assuming 2.85 gear ratio for brushless motor differential: https://forums.traxxas.com/showthread.php?9080733-Diff-gear-ratios
*/
//boolean rpm_period_updated = false; //rpms must be updated every 100 ms, otherwise the car has stopped, and velocity data should show 0 m/s
void rpm_feedback()
{
//Serial.println("in rpm_feedback");
last_rpm_pulse_update_ms = millis(); //notice the 'ms' here we want to use millisecond for checking whether or not data is valid. millis() can count up to 50 days while micros() only counts up to 70 minutes, thus millis() is used here.
unsigned long time_now = micros(); //use time now for accurate time calculations
unsigned long rev_period_temp = time_now - last_rpm_pulse_time_us; //get spur-gear revolution period
if(rev_period_temp > 0) rev_period = rev_period_temp; //revs are within
else rev_period = REV_PERIOD_MAX_US;
last_rpm_pulse_time_us = time_now; //using 'time_now' ensures that the time taken to get to this point in code does not interfere with rev_period accuracy - - - micros(); //reset time
if(pos[MOTOR_ID] < 90) //determine the direction that the vehicle is traveling in
{
forward = false;
}else forward = true;
//rpm_period_updated = true; not needed, only last_rpm_pulse_time_ms is needed for checking
}
void setup() {
// put your setup code here, to run once:
pinMode(RPM_FEEDBACK_PIN, INPUT_PULLUP);
attachInterrupt(RPM_FEEDBACK_PIN, rpm_feedback,FALLING); //arduino reference recommends using digitalPinToInterrupt(RPM_FEEDBACK_PIN) but the command is not recognized here
analogReference(EXTERNAL); //Using external reference for servo position
for(int i = 0; i < N; i++) //initialize
{
pos[i] = 90;
servo[i].attach(ESC_PIN + i);
}
Serial.begin(115200);
}
void loop() {
// put your main code here, to run repeatedly:
if(Serial.available() >= 1)
{
if(Serial.read() == 'G')
{
unsigned long t = millis();
while((Serial.available() < 3) && ((millis() - t) < 10)); //wait for the rest of the package, or timeout
if(Serial.available() >= 3)
{
char buf[3];
Serial.readBytes(buf, 3);
if((buf[0] == 'O') && (buf[1] >= 0) && (buf[1] < 2))
{
pos[buf[1]] = byte(buf[2]);
if(buf[1] == MOTOR_ID) lastTimeMotorData = millis(); //time stamp of last motor data retrieval
//Serial.print("buf[2]: ");
//Serial.println(byte(buf[2]), DEC);
//Serial.print("pos: ");
//Serial.println(pos[buf[1]]);
}
}
}
}
if((millis() - lastTimeMotorData) > MOTOR_DATA_TIMEOUT) pos[MOTOR_ID] = NEUTRAL; //stop the motor if data is not being received
for(int i = 0; i < N; i++)
{
servo[i].write(pos[i]);
}
if((millis() - lastTime_servoFeedback) >= 50) // 20Hz 20) //50Hz matches current ROS driver settings
{
lastTime_servoFeedback = millis();
int servo_feedback = analogRead(SERVO_FEEDBACK_PIN);
Serial.write('G'); //PID
Serial.write('O');
Serial.write(SERVO_ID);
//Serial.print(servo_feedback);
Serial.write(lowByte(servo_feedback));
Serial.write(highByte(servo_feedback));
//Serial.println(servo_feedback);
float rev_frequency;
if((last_rpm_pulse_update_ms + 100) < millis()) rev_frequency = 0; //use millis() since it can count up to 50 days, and will not have a chance of a hiccup after 70 minutes of using micros()
//instead, correct period when slowing down, also stop when the maximum threshold is reached
//if((micros() - last_rpm_pulse_time_us) >= REV_PERIOD_MAX_US) rev_frequency = 0; //car is stopped in this case. I decided not to try correcting the period as mentioned above
else rev_frequency = (float) 1/rev_period*1000000;
byte *rev_freq_bytes_to_transmit = (byte *) &rev_frequency;
if(forward == false) rev_frequency = -rev_frequency; //a negative frequency is used for reverse
Serial.write('G'); //PID
Serial.write('O');
Serial.write(MOTOR_ID); //used for addressing
Serial.write(rev_freq_bytes_to_transmit, 4);
}
}
一些好的信息可能是：
snuc@usuavc:~$ udevadm info -a -n /dev/ttyACM0
Udevadm info starts with the device specified by the devpath and then
walks up the chain of parent devices. It prints for every device
found, all possible attributes in the udev rules key format.
A rule to match, can be composed by the attributes of the device
and the attributes from one single parent device.
looking at device '/devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4:1.0/tty/ttyACM0':
KERNEL=="ttyACM0"
SUBSYSTEM=="tty"
DRIVER==""
looking at parent device '/devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4:1.0':
KERNELS=="1-4:1.0"
SUBSYSTEMS=="usb"
DRIVERS=="cdc_acm"
ATTRS{authorized}=="1"
ATTRS{bAlternateSetting}==" 0"
ATTRS{bInterfaceClass}=="02"
ATTRS{bInterfaceNumber}=="00"
ATTRS{bInterfaceProtocol}=="01"
ATTRS{bInterfaceSubClass}=="02"
ATTRS{bNumEndpoints}=="01"
ATTRS{bmCapabilities}=="6"
ATTRS{supports_autosuspend}=="1"
looking at parent device '/devices/pci0000:00/0000:00:14.0/usb1/1-4':
KERNELS=="1-4"
SUBSYSTEMS=="usb"
DRIVERS=="usb"
ATTRS{authorized}=="1"
ATTRS{avoid_reset_quirk}=="0"
ATTRS{bConfigurationValue}=="1"
ATTRS{bDeviceClass}=="02"
ATTRS{bDeviceProtocol}=="00"
ATTRS{bDeviceSubClass}=="00"
ATTRS{bMaxPacketSize0}=="8"
ATTRS{bMaxPower}=="100mA"
ATTRS{bNumConfigurations}=="1"
ATTRS{bNumInterfaces}==" 2"
ATTRS{bcdDevice}=="0001"
ATTRS{bmAttributes}=="c0"
ATTRS{busnum}=="1"
ATTRS{configuration}==""
ATTRS{devnum}=="4"
ATTRS{devpath}=="4"
ATTRS{idProduct}=="0043"
ATTRS{idVendor}=="2341"
ATTRS{ltm_capable}=="no"
ATTRS{manufacturer}=="Arduino (www.arduino.cc)"
ATTRS{maxchild}=="0"
ATTRS{quirks}=="0x0"
ATTRS{removable}=="removable"
ATTRS{serial}=="55330313635351207081"
ATTRS{speed}=="12"
ATTRS{urbnum}=="6990"
ATTRS{version}==" 1.10"
looking at parent device '/devices/pci0000:00/0000:00:14.0/usb1':
KERNELS=="usb1"
SUBSYSTEMS=="usb"
DRIVERS=="usb"
ATTRS{authorized}=="1"
ATTRS{authorized_default}=="1"
ATTRS{avoid_reset_quirk}=="0"
ATTRS{bConfigurationValue}=="1"
ATTRS{bDeviceClass}=="09"
ATTRS{bDeviceProtocol}=="01"
ATTRS{bDeviceSubClass}=="00"
ATTRS{bMaxPacketSize0}=="64"
ATTRS{bMaxPower}=="0mA"
ATTRS{bNumConfigurations}=="1"
ATTRS{bNumInterfaces}==" 1"
ATTRS{bcdDevice}=="0415"
ATTRS{bmAttributes}=="e0"
ATTRS{busnum}=="1"
ATTRS{configuration}==""
ATTRS{devnum}=="1"
ATTRS{devpath}=="0"
ATTRS{idProduct}=="0002"
ATTRS{idVendor}=="1d6b"
ATTRS{interface_authorized_default}=="1"
ATTRS{ltm_capable}=="no"
ATTRS{manufacturer}=="Linux 4.15.0-32-generic xhci-hcd"
ATTRS{maxchild}=="12"
ATTRS{product}=="xHCI Host Controller"
ATTRS{quirks}=="0x0"
ATTRS{removable}=="unknown"
ATTRS{serial}=="0000:00:14.0"
ATTRS{speed}=="480"
ATTRS{urbnum}=="76"
ATTRS{version}==" 2.00"
looking at parent device '/devices/pci0000:00/0000:00:14.0':
KERNELS=="0000:00:14.0"
SUBSYSTEMS=="pci"
DRIVERS=="xhci_hcd"
ATTRS{broken_parity_status}=="0"
ATTRS{class}=="0x0c0330"
ATTRS{consistent_dma_mask_bits}=="64"
ATTRS{d3cold_allowed}=="1"
ATTRS{dbc}=="disabled"
ATTRS{device}=="0x9d2f"
ATTRS{dma_mask_bits}=="64"
ATTRS{driver_override}=="(null)"
ATTRS{enable}=="1"
ATTRS{irq}=="122"
ATTRS{local_cpulist}=="0-7"
ATTRS{local_cpus}=="ff"
ATTRS{msi_bus}=="1"
ATTRS{numa_node}=="-1"
ATTRS{revision}=="0x21"
ATTRS{subsystem_device}=="0x2070"
ATTRS{subsystem_vendor}=="0x8086"
ATTRS{vendor}=="0x8086"
looking at parent device '/devices/pci0000:00':
KERNELS=="pci0000:00"
SUBSYSTEMS==""
DRIVERS==""
我认为问题出在串口的ROS版本上。我决定尝试一些原生的linux库，termios，并成功写入端口！
我找到了这个示例代码：https://en.wikibooks.org/wiki/Serial_Programming/Serial_Linux
问题在于以某种方式进行ros串行安装。
不知道你是否还想用serial / serial.h来解决这个问题，但我认为你的问题可能在于超时设置。
我告诉你这个，因为我有完全相同的问题，我可以读取传入的数据，但无法写入。
/ dev / ttyUSB0权限没问题，但没有超时。
我在互联网上找到了以下配置，试了一下工作。现在我可以读写了。
try{
ser.setPort("/dev/ttyUSB0");
ser.setBaudrate(9600);
serial::Timeout to = serial::Timeout::simpleTimeout(10);
ser.setTimeout(to);
ser.open();
return true;
}
catch (SerialException e) {
return 0;