I am trying to send values from ADC through USB using "CDC_Transmit_FS()"
On the receiving side, I am receiving data using readline() and decoding the 'string' to 'int'
The code works fine but occasionally I receive for example, b'\x00234\n' instead of b'1234\n', which raises decoding error.
Do you know why does '\x' appear?
One more question is: Is there any smarter method to send ADC values through USB instead of converting int values to string?
I want to make the transmission faster.
thanks in advance!
uint32_t adcbuff[sample];
char endofpacket[5] = {'9', '9', '9', '9', '\n'};
char txbuff[sample*5];
while(1)
{
HAL_ADC_Start_DMA(&hadc2,(uint32_t*)adcbuff, sample);
for(i = 0; i < sample; i++)
{
sprintf (tempbuff, "%u\n", ((adcbuff[i] * 5000) / 0xFFFF)-2000);
strcat( txbuff,tempbuff);
}
strcat( txbuff,endofpacket);
CDC_Transmit_FS( (uint8_t*)txbuff, strlen(txbuff));
strcpy(txtbuff,"");
}
not enough rep to post as a comment
Usually \x is an indication of a hexadecimal value. Could it be that a non alphanumeric value is being received?
For troubleshooting, I would temporarily change
sprintf (tempbuff, "%u\n", ((adcbuff[i] * 5000) / 0xFFFF)-2000); to
sprintf (tempbuff, "%s\n", ((adcbuff[i] * 5000) / 0xFFFF)-2000); to see what kind of characters are being sent over. (Maybe sprintf to a tmp file instead.)
b'\x00234\n' - This means that first byte is 0! Not ASCII 0 = 0x30, but just 0.
Probably this is effect of strcat - after concatenating this function adds '\0' at the end of string.
Instead of using sprintf, just redirect stdout to USB-CDC and use printf:
int _write(int file, char *ptr, int len)
{
UNUSED(file);
CDC_Transmit_FS((uint8_t*)ptr, len);
while (hcdc->TxState != 0);
return len;
}
If you want to send all at once use setvbuf for stdout with _IOFBF and call fflush(stdout);
Related
I'm trying to take data read from a TCP socket with the g_io_channel_read_chars method and convert it into a long integer. I've tried using strtol, atoi, not casting ScanLine as a gchar pointer, accessing the first variable of ScanLine with ScanLine[0], declaring FilterAmount in different ways and despite that, my app still crashes on that line. Any ideas?
static gchar ScanLine[9640];
long int FilterAmount;
g_io_channel_read_chars (source, (gchar *) ScanLine,1,&BytesRead,&GlibError);
if (BytesRead != 1){
return TRUE;
}
printf("This is my string: %s\n", ScanLine);
FilterAmount = strtol(ScanLine, NULL, 10);
The output of the printf statement is "2"
strtol() takes a C string argument: this means the character array must be NULL-terminated. Yours is quite probably not. You must either add a terminator after the last byte you read or parse the digits yourself (since you know when to stop parsing).
I have been using the md5 implementation found in this page:
http://www.zedwood.com/article/121/cpp-md5-function
As it is it works fine. There is however this function:
// return hex representation of digest as string
std::string MD5::hexdigest() const
{
if (!finalized)
return "";
char buf[33];
for (int i=0; i<16; i++)
sprintf(buf+i*2, "%02x", digest[i]);
buf[32]=0;
return std::string(buf);
}
If I change sprintf to the safe version (sprintf_s), then I get an Access Violation Error at runtime. The only thing I change is the sprintf line, like this:
sprintf_s(buf+i*2, 33, "%02x", digest[i]);
It compiles fine but then I get the error. Any idea why ?
Since you pass an offset into your buffer, you also need to reduce the size you pass to snprintf_s. That is:
snprintf_s(buf+i*2, 33-2*i, "%02x", digest[i]);
-(void)InitWithPwd:(char *)pPwd
{
char szResult[17];
//generate md5 checksum
CC_MD5(pPwd, strlen(pPwd),&szResult[0]);
szResult[16] = 0;
m_csPasswordHash[0]=0;
for(int i = 0;i < 16;i++)
{
char sz[3] = {'\0'};
//crash in blow row. The first pass is ok. The third pass crash.
//I can't understand.
sprintf(&sz[0],"%2.2x",szResult[i]);
strcat(m_csPasswordHash,sz);
}
m_csPasswordHash[32] = 0;
printf("pass:%s\n",m_csPasswordHash);
m_ucPacketType = 1;
}
I want to get the md5 of the password. But above code crash again and again. I can't understand why.
Your buffer (sz) is too small, causing sprintf() to generate a buffer overflow which leads to undefined behavior, in your case a crash.
Note that szResult[1] might be a negative value when viewed as an int (which happens when passing a char-type value to sprintf()), which can cause sprintf() to disregard your field width and precision directives in order to format the full value.
Here is an example showing this problem. The example code is written in C, but that shouldn't matter for this case.
This solves the problem by making sure the incoming data is considered unsigned:
sprintf(sz, "%02x", (unsigned char) szResult[i]);
I'm doing a small app for evaluating and analyzing transfer functions. As boring as the subject might seem to some, I want it to at least look extra cool and pro and awesome etc... So:
Step 1: Gimme teh coefficients! [A bunch of numbers]
Step 2: I'll write the polynomial with its superscripts. [The bunch of numbers in a string]
So, I write a little C parser to just print the polynomial with a decent format, for that I require a wchar_t string that I concatenate on the fly. After the string is complete I quickly try printing it on the console to check everything is ok and keep going. Easy right? Welp, I ain't that lucky...
wchar_t *polynomial_description( double *polyArray, char size, char var ){
wchar_t *descriptionString, temp[100];
int len, counter = 0;
SUPERSCRIPT superscript;
descriptionString = (wchar_t *) malloc(sizeof(wchar_t) * 2);
descriptionString[0] = '\0';
while( counter < size ){
superscript = polynomial_utilities_superscript( size - counter );
len = swprintf(temp, 100, L"%2.2f%c%c +", polyArray[counter], var, superscript);
printf("temp size: %d\n", len);
descriptionString = (wchar_t *) realloc(descriptionString, sizeof(wchar_t) * (wcslen(descriptionString) + len + 1) );
wcscat(descriptionString, temp);
counter++;
}
//fflush(stdout); //Already tried this
len = wprintf(L"%ls\n", descriptionString);
len = printf("%ls**\n", descriptionString);
len = fprintf(stdout, "%ls*\n", descriptionString);
len = printf("FFS!! Print something!");
return descriptionString;
}
During the run we can see temp size: 8 printed the expected number of times ONLY WHILE DEBUGGING, if I run the program I get an arbitrary number of prints each run. But after that, as the title states, wprintf, printf and fprintf don't print anything, yet len does change its size after each call.
In the caller function, (application:(UIApplication *)application didFinishLaunchingWithOptions:, while testing) I put an NSLog to print the return string, and I dont get ANYTHING not even the Log part.
What's happening? I'm at a complete loss.
Im on XCode 4.2 by the way.
What's the return value from printf/wprintf in the case where you think it's not printing anything? It should be returning either -1 in the case of a failure or 1 or more, since if successful, it should always print at least the newline character after the description string.
If it's returning 1 or more, is the newline getting printed? Have you tried piping the output of your program to a hex dumper such as hexdump -C or xxd(1)?
If it's returning -1, what is the value of errno?
If it turns out that printf is failing with the error EILSEQ, then what's quite likely happening is that your string contains some non-ASCII characters in it, since those cause wcstombs(3) to fail in the default C locale. In that case, the solution is to use setlocale(3) to switch into a UTF-8 locale when your program starts up:
int main(int argc, char **argv)
{
// Run "locale -a" in the Terminal to get a list of all valid locales
setlocale(LC_ALL, "en_US.UTF-8");
...
}
I'm trying to allow users to simply hit Enter without typing anything, and use this to mean accepting a default value. scanf isn't doing what I want and the app still 'blocks': the next line of code doesn't run.
The only way is to actually type something THEN press Enter.
I tried using NSFileHandle and fileHandleWithStandardInput; however, it seems that the user is now forced to hit Ctrl-D to indicate EOF.
Someone suggested using fgets, but I cannot work out what to pass as 3rd parameter (of FILE* type). Tried stdin but it doesn't 'block'.
How do I accept input from a user, using Objective-C, and at the same time allow the user to simply hit Enter without being forced to type anything? How do I read a single line, even if that line is blank?
Assuming the code doesn't block and the next line runs immediately (as you seemed to indicate early in the question and in a comment), you have a common problem when mixing non-line-based and line-based input.
What happens is you have a newline left in the buffer, and fgets sees that, reads it, and returns, instead of doing what you really want: ignoring it, and then reading a line.
The solution is to simply do the ignoring part yourself, and then call fgets:
#include <stdio.h>
#include <string.h>
FILE* ignoreline(FILE* stream) {
for (int c; (c = fgetc(stream)) != EOF;) {
if (c == '\n') break;
}
return stream;
}
void example_use() {
char buf[1000];
ignoreline(stdin);
fgets(buf, sizeof buf, stdin);
// or, since it returns the stream, can be more compact:
fgets(buf, sizeof buf, ignoreline(stdin));
}
int main() { // error handling omitted
int n;
printf("Enter a number: ");
scanf("%d", &n);
char buf[1000];
printf("Enter a line: ");
ignoreline(stdin); // comment this line and compare the difference
fgets(buf, sizeof buf, stdin);
*strchr(buf, '\n') = '\0';
printf("You entered '%s'.\n", buf);
return 0;
}
Note that it is also common and encouraged to "pair" the ignoreline with the scanf (or other non-line-based input) to turn that into line-based input. You may want to modify it, in that case, so you can tell the difference between input of "42 abc" and "42" (in the "Enter a number" case). Some people just use fgets everywhere, then parse that line with sscanf, and while that works, it's not necessary.
I use getch(); in library conio.h
simply the program waits for any key to be pressed
If you're using Windows, you can use the ReadConsoleInput function (see MSDN for more on this) :
INPUT_RECORD keyin;
DWORD r;
while (ReadConsoleInput(GetStdHandle(STD_INPUT_HANDLE),&keyin,1,&r)) {
if (keyin.EventType!=KEY_EVENT) continue;
if (keyin.Event.KeyEvent.wVirtualKeyCode==VK_SPACE) break; ///use these VK codes to get any key's input
if (keyin.Event.KeyEvent.wVirtualKeyCode==VK_F1)
{
printf("You pressed F1\n");
}
if (keyin.Event.KeyEvent.wVirtualKeyCode==VK_F2)
{
printf("You pressed F2\n",);
}
}//end while loop
You don't need to hit enter after each key then.This works like a dream for me...
use getchar() to take input without using scanf function...