I have two int values:
v_y
v_x
That I would like to convert to a size 2 char array then write to my serial port.
I currently have this code that isn't working:
void Array2 (char charArray[], int sizeOfArray);
........
}
{
char one[] = { 'v_x', 'v_y' };
Array2(one, 2);
Serial::WriteData(one, 2);
}
}
I currently get two errors:
a nonstatic member reference must be relative to a specific object
and
'Serial::WriteData':illegal call of non-static member function.
Any help, hint or idea on what I'm doing wrong would be great!
Edit: I'm using this code to communicate with my serialport CODE
// data.h or similar, you need this for both the arduino and desktop machine
struct Data {
double v_x;
double v_y;
}
On your arduino: To write
Data data = {
.v_x = 1.0, // Example put your values here
.v_y = 2.0,
};
// This should write from your Arduino to the computer
Serial::WriteData((const char*)data, sizeof(data));
On your computer
Data data;
// This reads from the serial port, and put the data in the struct
auto len = SP->ReadData((const char*)data, sizeof(data));
// check that data is the right size
// use the data from data.v_x and data.v_y
auto v_x = data.v_x;
auto v_y = data.v_y; // etc
Related
I'm trying to get an array of tensorflow box predictions from C++ to golang, but I'm not able to do it no matter what I do. I have a GO program that calls a function that does tensorflow detections in C++ using cgo. This all works and I'm able to get the predictions in C++. The problem is to transfer these predictions into GO as an array of 100 structs that each hold one prediction.
I'm able to set a pointer in GO and use this pointer address to set one struct in C++. The code for this is seen below.
I want to set an array of structs in C++ and retreive this array in GO. I thought it should be easy to just use the same pointer address as earlier and use this as the address for my C++ array. Then I could restore the struct from the pointer in GO. Does anyone have a solution for this?
GO
type PredictResult struct {
Loc [4]float32
Score int
Label int
}
var predictions PredictResult
predictions_ptr := unsafe.Pointer(&predictions)
C.LIB_predict(predictions_ptr)
fmt.Println("GO predictions; ", predictions)
bridge.hpp
struct PredictResult{
float Loc[4];
int64_t Score;
int64_t Label;
};
void LIB_predict(void* predictions);
bridge.cpp
void LIB_predict(void* predictions){
PredictResult *p = (PredictResult*)predictions;
p->Score = 6;
p->Label = 95;
}
Prints:
GO predictions; {[0 0 0 0] 6 95}
Assuming your C function returns the array as PredictResult* and assuming you know the length of the returned array (in the example below I assume 10, but you can replace it by whatever works), this approach should work:
// #include <stdio.h>
// #include <stdlib.h>
//
// typedef struct PredictResult {
// float Loc[4];
// int64_t Score;
// int64_t Label;
// } PredictResult;
//
// PredictResult* getOneResult() {
// PredictResult* p = (PredictResult*)calloc(1, sizeof(PredictResult));
// p->Score = 10;
// p->Label = 99;
// p->Loc[1] = 2.5;
// p->Loc[3] = 3.5;
// return p;
// }
//
// PredictResult* getTenResults() {
// PredictResult* parr = (PredictResult*)calloc(10, sizeof(PredictResult));
// parr[0].Score = 10;
// parr[0].Label = 99;
// parr[0].Loc[1] = 2.5;
// parr[0].Loc[3] = 3.5;
//
// parr[4].Score = 44;
// parr[4].Label = 123;
// parr[4].Loc[1] = 12.25;
// parr[4].Loc[3] = -40.5;
// return parr;
// }
//
//
import "C"
type PredictResult C.struct_PredictResult
func main() {
p := C.getOneResult()
if p == nil {
log.Fatal("got nil")
}
pp := (*PredictResult)(p)
fmt.Println(pp)
parr := C.getTenResults()
if parr == nil {
log.Fatal("got nil")
}
pslice := (*[1 << 28]PredictResult)(unsafe.Pointer(parr))[:10:10]
fmt.Println(pslice)
}
What you'll be most interested in is how the result of getTenResults is converted to a Go slice of the appropriate struct type. This is employing the technique recommended on the Go wiki.
Depending on the exact signature of your C function you may need to write a "bridge" function in the import "C" part to provide the data as convenient to Go, but this is the basic gist of it.
As an alternative, if you wish to allocate the slice on the Go side and pass in a pointer to C to populate, you can do this:
// void PopulateTenResults(void* arr) {
// PredictResult* parr = (PredictResult*)arr;
// parr[1].Score = 210;
// parr[1].Label = 299;
// parr[1].Loc[1] = 22.5;
// parr[1].Loc[3] = 23.5;
//
// parr[8].Score = 344;
// parr[8].Label = 3123;
// parr[8].Loc[1] = 312.25;
// parr[8].Loc[3] = -340.5;
// }
//
//
import "C"
And then in Go do:
prslice := make([]PredictResult, 10)
C.PopulateTenResults(unsafe.Pointer(&prslice[0]))
fmt.Println(prslice)
Of course the hard-coded 10 is just for simplicity here; you could pass the length of arr as a parameter to C.
You can pass a pointer to the first element in a slice and the length of the slice to C++ and treat it like a C-style array.
I have an Arduino sketch that will be working on an Arduino UNO and I am trying to get uno to communicate over the i2c connection with a raspberry pi.
Problem is using wire.h library where method Wire.onRequest is working just fine when I use it like this.
#include <Wire.h>
#define COMM_DELAY 50
#define SLAVE_ADDRESS 0x04
int current_rule = 0;
void initI2c() {
// initialize i2c as slave
Wire.begin(SLAVE_ADDRESS);
// define callbacks for i2c communication
Wire.onReceive(receiveData);
}
// callback for received data
void receiveData(int byteCount) {
while (Wire.available()) {
current_rule = Wire.read();
}
}
but when I try to make this exact result with a class method, I get an error :
invalid use of non-static member function
(with Wire.onRequest(this->receiveData) line gets to be marked red)
Just like this:
void (*funptr)();
typedef void (*Callback)(byte);
class Comm{
public:
int callback_list_size = 0;
bool option_debug;
byte option_address;
int option_comm_delay;
void(*callback_list[256]);
byte *rules;
// function for receiving data. raspberry -> arduino
// Whenever the master sends new data, this method will call the appropriate callback.
void receiveData()
{
byte data;
Serial.println("[INFO] Received new data from master");
while (Wire.available())
{
data = Wire.read();
}
for (int i = 0; i < callback_list_size; i++)
{
if (rules[i] == data){
funptr = callback_list[i];
funptr();
}
}
}
// function for sending data. Called when raspberry request data. arduino -> raspberry
// Whenever the master requests data, this method will be called. For now we don't need this but anyway.
void sendData(int s)
{
if (option_debug)
Serial.println("[INFO] Master requests data!");
}
/* Constructor that takes 3 parameters at max. Only the adress is mandatory others are optional and will be filled with default values
:address - adress of slave(arduino) - Example 0x04
:delay - a delay is needed because I2C clock is quite slow compared to the CPU clock - 50
:debug - for debug purposes if true debug info will be sent to Serial interface - true/false
*/
Comm(byte address, int delay = 50, bool debug = false)
{
option_address = address;
option_comm_delay = delay;
option_debug = debug;
if (debug)
Serial.println("[INFO] Comm Object Created!");
}
// Function needs to be called to initialize the communication channel.
void initI2c()
{
Wire.begin(option_address);
Wire.onReceive(this->sendData);
Wire.onRequest(this->receiveData);
if (option_debug)
Serial.println("[INFO] I2C channel initialized");
}
// Function to add new callback for a rule.
// This function returns id of passed callback
int addCallback(Callback func, byte rule)
{
callback_list_size++;
// Enlarge rules array to keep 1 more byte
byte *temp = new byte[callback_list_size]; // create new bigger array.
for (int i = 0; i + 1 < callback_list_size; i++) // reason fo i+1 is if callback_list_size is 1 than this is the first initializition so we don't need any copying.
{
temp[i] = rules[i]; // copy rules to newer array.
}
delete[] rules; // free old array memory.
rules = temp; // now rules points to new array.
callback_list[callback_list_size - 1] = &func;
rules[callback_list_size - 1] = rule;
return callback_list_size;
}
};
Comm *i2c_comm;
void loop()
{
}
void setup()
{
Serial.begin(9600);
initI2C();
}
void initI2C()
{
i2c_comm = new Comm(0x04, 50, true);
i2c_comm->initI2c();
//Callback Definitions
i2c_comm->addCallback(&rule_1, 0x01);
i2c_comm->addCallback(&rule_2, 0x02);
i2c_comm->addCallback(&rule_3, 0x03);
i2c_comm->addCallback(&rule_4, 0x04);
}
I also tried to make the receiveData method to be static.
But in this case I have an error like this:
invalid use of member Com::callback_list_size in static member function
which makes sense to me as static method won't know which callback_list_size I am talking about.
so I am quite confused about how I can handle such a problem?
You're almost there. Generally speaking in C++ you need to pass a static class method for callback functions.
The error you received after changing your method to static is expected as you're trying to access a member of an instance of the class Comm which cannot be done in a static method in which there is no 'this'.
Here's one of many techniques to consider, but please read over the SO post Using a C++ class member function as a C callback function.
Anyway the approach here is to leverage a static pointer to an instance.
class Comm {
private:
static Comm* pSingletonInstance;
static void OnReceiveHandler() {
if (pSingletonInstance)
pSingletonInstance->receiveData();
}
static void OnSendHandler(int s) {
if (pSingletonInstance)
pSingletonInstance->sendData(s);
}
void initI2c() {
Comm::pSingletonInstance = this; // Assign the static singleton used in the static handlers.
Wire.onReceive(Comm::OnSendHandler);
Wire.onRequest(Comm::OnReceiveHandler);
Wire.begin(option_address);
}
}
// static initializer for the static member.
Comm* Comm::pSingletonInstance = 0;
Again there are many ways to get around this issue but above is an easy one and likely suitable for your project. If you need to manage multiple instances of Comm, you'll have to do something quite different.
Good luck!
I'm coding a plugin for XPLANE10 which gets a MSG from ROS.
My IDE is QTcreator 4.1.0 based QT 5.7.0 for Ubuntu 64 Bit. I would like to use C++11 Standards
My code explained
The main initializes ROS and creates a map -> container.
ROS spins in a loop till my GUI sends a MSG where my AirPlane should fly.
The MSG contains 3 floats(phi, theta, psi) where "phi" is the AirPlane ID, theta contains the ID for my ETA(Estimated Time of Arrival)
and psi contains the ID for my pose All of the IDs are saved in the ParameterServer(lookuptable).
So at the beginning i look up the activeAirplanes which returns a vector . I would like to store them in a map where the key is the AirCraft ID and the second param is an instance of the Object.
So i have initialized the for example(looked in container while debugging):
[0] first = 1 // Airplane ID1
[0] second = new CObject(freq)
[1] first = 2 // Airplane ID2
[1] second = new CObject(freq)
If i get a MSG from GUI
phi = 1
theta=2
psi=3
,
ROS will callback
MSG(....std::map<i32, CObject> &container)
// if phi is 1 so use the mapkey 1 and trigger the method do_stuff from CObject
do_stuff(phi, theta, psi,freq)
I would like to call the in a function from main
int getPlanes(std::map<i32,CObject>& container)
{
...
getActiveAirplanesFromServer(activePlanes);
}
First Question:
How do i pass the container to my callback?
Second Question:
How do i parallelize do_stuff() so my callback will return to main and i'm able to command more aircrafts while the others are calculated?
Third Question:
How would be the correct syntax for getPlanes to pass the container by reference so getPlanes() can edit it?
Fourth Question:
Is there a difference between
std::map<i32,CObject*> map
std::map<i32,CObject>* map
and
std::map<i32,CObject*>::iterator it=container->begin();
std::map<i32,CObject*>::iterator* it=container->begin();
If yes, what do i want ? #4Solved
// I have to edit stuff 'cause of some restrictions in my company.
#include "Header.h"
int main()
{
f64 freq = 10;
std::map<i32, CObject>* container;
std::map<i32,CObject>::iterator* it=container->begin();
// ROS
if(!ros::isInitialized())
{
int rosargc = 0;
char** rosargv = NULL;
ros::init(rosargc, rosargv, "MainNode");//), ros::init_options::AnonymousName);
}
else
{
printf("Ros has already been initialized.....\n");
}
ros::NodeHandle* mainNodeHandle=new ros::NodeHandle;
ros::AsyncSpinner spinner(2);
ParameterServer * ptrParam= new ParameterServer(mainNodeHandle);
ros::Subscriber airSub=mainNodeHandle->subscribe<own_msgs::ownStruct>("/MSG",
1000,
boost::bind(MSG,
_1,
freq,
container));
std::vector<i32> activePlanes;
i32 retVal=0;
retVal += ptrParam-> ParameterServer::getActiveAirplanesFromServer(activePlanes);
if (retVal == 0 && activePlanes.size()>0)
{
for (u32 j =0; j <activePlanes.size(); j++)
{
container->insert (std::pair<i32,CObject> (activePlanes[j] , new CObject(freq)));
}
}
while (ros::ok())
{
spinner.start(); //spinnt sehr viel :-)
ros::waitForShutdown ();
}
std::cout<<"ENDE"<<std::endl;
int retval = 1;
return retval;
}
void MSG(const own_msgs::ownStruct<std::allocator<void> >::ConstPtr &guiMSG,
f64 freq,
std::map<i32, CObject> &container)
{
if ((guiMSG->phi != 0) && (guiMSG->theta != 0) && (guiMSG->psi != 0))
{
std::string alpha = std::to_string(guiMSG->phi)+std::to_string(guiMSG->theta)+to_string(guiMSG->psi);
container.at(guiMSG->phi) -> do_stuff(guiMSG->phi,guiMSG->theta,guiMSG->psi, freq);
}
else
{
std::cout<<" Did not receive anything\n"<<endl;
}
}
void do_stuff(...)
{
//copy the IDs to private Member of this single Object
//setROS() for this single Object
//callback the current AC pose via ID from XPLANE
//callback the wished AC pose via ID from ParamServer
// do some calculations for optimum flight path
// publish the Route to XPlane
}
EDIT::
Problem is i get it to compile now and if debug it and set a breakpoint at :
void MSG(const own_msgs::ownStruct<std::allocator<void> >::ConstPtr &guiMSG,f64 freq,std::map<i32, CObject*> &container)
{
..
/*->*/ container.at(guiMSG->)...
}
The Container remains empty.
So i read some stuff about pointers and i saw my errors..
I confused * and &
if i want to pass the adress of a variable i have to write like
int main()
{
int a = 0;
AddTwo(&a)
cout<<a<<endl; // Output: 2
}
void AddTwo(int* a)
{
a+=2;
}
I'm using a third party library which defines this struct:
typedef struct
{
unsigned short nbDetectors;
//! structure of detector status
struct DetectorStatus
{
unsigned int lastError; //< last detector internal error
float temperature; //< detector temperature
detector_state state; //< detector state
unsigned short mode; //< detector mode
struct EnergyStatus
{
power_source powerSource; //< front-end power source
frontend_position frontendPosition; //< front-end position relative to the docking station
struct BatteryStatus
{
bool present; //< battery present or not in the detector
unsigned short charge; //< charge level of the battery (in %)
float voltageLevel; //< battery voltage level
float temperature; //< temperature of the battery
unsigned short chargeCycles; //< number of charge/discharge cycles
unsigned short accuracy; //< Expected accuracy for charge level (in %)
bool needCalibration;
} batteryStatus;
} * energyStatus;
struct GridStatus
{
detector_grid grid;
} * gridStatus;
} * detectorStatus;
} HardwareStatus;
This struct is used by the library as data passed by one of its callbacks. So it's the library which fills it up, I just read it. So far, so good.
But now I'm writing an emulator for the device handled by this library, so now I have to fill up one of these structs and I can't get it right.
I tried this:
HardwareStatus status;
status.detectorStatus->temperature = 20 + rand() % 10;
e.data = &status;
m_pContext->EventCallback( EVT_HARDWARE_STATUS, &e );
When I compiled, I got:
warning C4700: uninitialized local variable 'status' used
Then I realized... The pointers inside the struct are pointing to garbage, nice catch Visual Studio! So then I tried to start by declaring an instance of the innermost struct (BatteryStatus), but that wouldn't compile... because it's not typedef'd (it says the BatteryStatus type is not defined)? So I got stumped... How do I fill the struct up?
if you want to have everything on the stack this should do it:
// Getting structs on the stack initialized to zero
HardwareStatus status = { 0 };
HardwareStatus::DetectorStatus detectorStatus = { 0 };
HardwareStatus::DetectorStatus::EnergyStatus energyStatus = { 0 };
HardwareStatus::DetectorStatus::GridStatus gridStatus = { 0 };
// "Linking" structs
detectorStatus.energyStatus = &energyStatus;
detectorStatus.gridStatus = &gridStatus;
status.detectorStatus = &detectorStatus;
// Now you can fill and use them
status.detectorStatus->temperature = 20 + 3 % 10;
//...
You could value-iniitialize it:
HardwareStatus status = {};
If you want to instantiate a BatteryStatus, you can do that by fully qualifying the name:
HardwareStatus::DetectorStatus::EnergyStatus::BatteryStatus bs;
did you try memset'ing the struct to 0 ?
I have a situation in Visual C++ 2008 that I have not seen before. I have a class with 4 STL objects (list and vector to be precise) and integers.
It has a method:
inline int id() { return m_id; }
The return value from this method is corrupt, and I have no idea why.
debugger screenshot http://img687.imageshack.us/img687/6728/returnvalue.png
I'd like to believe its a stack smash, but as far as I know, I have no buffer over-runs or allocation issues.
Some more observations
Here's something that puts me off. The debugger prints right values in the place mentioned // wrong ID.
m_header = new DnsHeader();
assert(_CrtCheckMemory());
if (m_header->init(bytes, size))
{
eprintf("0The header ID is %d\n", m_header->id()); // wrong ID!!!
inside m_header->init()
m_qdcount = ntohs(h->qdcount);
m_ancount = ntohs(h->ancount);
m_nscount = ntohs(h->nscount);
m_arcount = ntohs(h->arcount);
eprintf("The details are %d,%d,%d,%d\n", m_qdcount, m_ancount, m_nscount, m_arcount);
// copy the flags
// this doesn't work with a bitfield struct :(
// memcpy(&m_flags, bytes + 2, sizeof(m_flags));
//unpack_flags(bytes + 2); //TODO
m_init = true;
}
eprintf("Assigning an id of %d\n", m_id); // Correct ID.
return
m_header->id() is an inline function in the header file
inline int id() { return m_id; }
I don't really know how best to post the code snippets I have , but here's my best shot at it. Please do let me know if they are insufficient:
Class DnsHeader has an object m_header inside DnsPacket.
Main body:
DnsPacket *p ;
p = new DnsPacket(r);
assert (_CrtCheckMemory());
p->add_bytes(buf, r); // add bytes to a vector m_bytes inside DnsPacket
if (p->parse())
{
read_packet(sin, *p);
}
p->parse:
size_t size = m_bytes.size(); // m_bytes is a vector
unsigned char *bytes = new u_char[m_bytes.size()];
copy(m_bytes.begin(), m_bytes.end(), bytes);
m_header = new DnsHeader();
eprintf("m_header allocated at %x\n", m_header);
assert(_CrtCheckMemory());
if (m_header->init(bytes, size)) // just set the ID and a bunch of other ints here.
{
size_t pos = DnsHeader::SIZE; // const int
if (pos != size)
; // XXX perhaps generate a warning about extraneous data?
if (ok)
m_parsed = true;
}
else
{
m_parsed = false;
}
if (!ok) {
m_parsed = false;
}
return m_parsed;
}
read_packet:
DnsHeader& h = p.header();
eprintf("The header ID is %d\n", h.id()); // ID is wrong here
...
DnsHeader constructor:
m_id = -1;
m_qdcount = m_ancount = m_nscount = m_arcount = 0;
memset(&m_flags, 0, sizeof(m_flags)); // m_flags is a struct
m_flags.rd = 1;
p.header():
return *m_header;
m_header->init: (u_char* bytes, int size)
header_fmt *h = (header_fmt *)bytes;
m_id = ntohs(h->id);
eprintf("Assigning an id of %d/%d\n", ntohs(h->id), m_id); // ID is correct here
m_qdcount = ntohs(h->qdcount);
m_ancount = ntohs(h->ancount);
m_nscount = ntohs(h->nscount);
m_arcount = ntohs(h->arcount);
You seem to be using a pointer to an invalid class somehow. The return value shown is the value that VS usually uses to initialize memory with:
2^32 - 842150451 = 0xCDCDCDCD
You probably have not initialized the class that this function is a member of.
Without seeing more of the code in context.. it might be that the m_id is out of the scope you expect it to be in.
Reinstalled VC++. That fixed everything.
Thank you for your time and support everybody! :) Appreciate it!