I have a char[32] that consist of ASCII characters, some of which may be non printable characters, however, they are all in valid range of 0 to 255.
Let's say, it contains these numbers:
{ 9A 2E 5C 66 26 3D 5A 88 76 26 F1 09 B5 32 DE 10 91 3E 68 2F EA 7B C9 52 66 23 9D 77 16 BB C9 42 }
I'd like to print out or store in std::string as "9A2E5C66263D5A887626F109B532DE10913E682FEA7BC95266239D7716BBC942", however, if I print it out using printf or sprintf, it will yield the ASCII representative of each number, and instead it will print out "ö.\f&=Zàv&Ò µ2fië>h/Í{…Rf#ùwª…B", which is the correct ASCII character representation, since: ö = 9a, . = 2e, ...
How do I reliably get the string representation of the hex numbers? ie: I'd expect a char[64] which contains "9A2E5C66263D5A887626F109B532DE10913E682FEA7BC95266239D7716BBC942" instead.
Thanks!
void bytesToHex(char* dest, char* src, int size) {
for (unsigned int i = 0; i < size; i++) {
sprintf(&dest[i * 2], "%02x", src[i]);
}
}
You'd have to allocate your own memory here.
It would be used like this:
char myBuffer[32]
char result[65];
bytesToHex(result, myBuffer, 32);
result[64] = 0;
// print it
printf(result);
// or store it in an std::string
std::string str = string(result);
I tried:
char szStringRep[64];
for ( int i = 0; i < 32; i++ ) {
sprintf( &szStringRep[i*2], "%x", szHash[i] );
}
it works as intended, but if it encountered a < 0x10 number, it will null terminated as it is printing 0
You can encode your string to another system like Base64, which is widely used when using encryption algorithms.
Related
I try read dtc codes using a obd device (sparkfun obd based on stn1110) and an arduino. Running this code
uint16_t codes[6];
byte dtcCount = obd.readDTC(codes, 6);
if (dtcCount == 0) {
Serial.println("No DTC");
} else {
Serial.print(dtcCount);
Serial.print(" DTC:");
for (byte n = 0; n < dtcCount; n++) {
Serial.print(' ');
Serial.print(codes[n], HEX);
}
Serial.println();
}
delay(5000);
}
Returns:
2 DTC: 3303 100
How can I interpret those codes? I mean usually I saw error codes are like PXXXX ...
Thanks a lot
L.E.
I scanned same car using a "proffesional" tester and found following codes (see pictures).
What I am doing wrong with my code or how should I interpret my results in order to get same codes as the service scanner?
Basically my code show 2 dtc's but the scanner found 5 in total
Dig further and I think the function used for read dtc is somehow wrong:
this is the function
byte COBD::readDTC(uint16_t codes[], byte maxCodes)
{
byte codesRead = 0;
for (byte n = 0; n < 6; n++) {
char buffer[128];
sprintf_P(buffer, n == 0 ? PSTR("03\r") : PSTR("03%02X\r"), n);
write(buffer);
if (receive(buffer, sizeof(buffer)) > 0) {
Serial.print("received buffer :");
Serial.println(buffer);
if (!strstr_P(buffer, PSTR("NO DATA"))) {
char *p = strstr(buffer, "43");
if (p) {
while (codesRead < maxCodes && *p) {
p += 6;
if (*p == '\r') {
p = strchr(p, ':');
if (!p) break;
p += 2;
}
uint16_t code = hex2uint16(p);
if (code == 0) break;
codes[codesRead++] = code;
}
}
break;
}
}
}
return codesRead;
}
As you see I printed "received buffer" to see what I get from OBD and the result is:
received buffer :43 01 33 03 01 00 00
>
I think is something wrong here, or I miss something in the answer
why i get that">" on a new line?
also according to https://en.wikipedia.org/wiki/OBD-II_PIDs (chapter Service 03 (no PID required))
i delete "43" from my buffer and get "01 33 03 01 00 00"
then "01" means "C - Chassis"
but then nothing match to the decoding description...so I became almost sure that I don t ask / read as it should this thing. I think i get an invalid answer somehow ...
Again any help will be appreciated :)
Thanks
L.E.2 - did another progess step.
According to this document - https://www.elmelectronics.com/wp-content/uploads/2016/07/ELM327DS.pdf , on page 34
first should find out the number of dtc stored and then try to read them.
Sending >0101 to obd return me "41 01 82 07 61 01"
and if I do 82 - 80 => I have 2 trouble codes ?!?! why I have 5 of them on the tester?
From my previous response, also according to that document
"43 01 33 03 01 00 00" means P0133 and P0301
But on the tester, except those 2, I had also - P0303 , P0300 and C1513
How to get to read correctly the dtc codes?
Thanks again
i have an byte array that i need to convert to ascii string before i save it as a system variable.
so i have a byte array like [63 6c 65 61 72]. i need to convert it to 'clear' before i store it in a system variable.
for (i = 0; i < elcount(gByteValue); i++)
{
snprintf(tmp, elcount(tmp), "%.2X ", gByteValue[i]); // byte to HEX convert
strncat(gStringValue, tmp, elcount(gStringValue)); // Concatenate HEX value to output string
}
write("String : %s", gStringValue);
const arr = new Uint16Array(2);
arr[0] = 5000;
arr[1] = 4000;
// Copies the contents of `arr`.
const buf1 = Buffer.from(arr);
// Shares memory with `arr`.
const buf2 = Buffer.from(arr.buffer);
console.log(buf1, buf2 );
// Prints: <Buffer 88 a0>
// Prints: <Buffer 88 13 a0 0f>
i look at the nodejs document where i see that
and my question is why buf1 is not <Buffer 88 13 a0 0f> ?
It is explained here that Buffer.from behaves as new Uint8Array() which can only contain numbers from 0 to 255 (1 byte) and here is stated that each value is converted and the result array length will be the same (so it can't have 4 elements). When converted, 2 byte value will be trimmed to 1 byte value, ignoring the second byte (88 13 -> 88, a0 0f -> a0).
I have the following message:
message Message {
int64 id = 1;
google.protobuf.FloatValue weight = 2;
google.protobuf.FloatValue override_weight = 3;
}
and I wish to change the type of weight and override_weight(optional fields) to google.protobuf.DoubleValue so what I did was the fllowing:
message Message {
int64 id = 1;
oneof weight_oneof {
google.protobuf.FloatValue weight = 2 [deprecated=true];
google.protobuf.DoubleValue double_weight = 4;
}
oneof override_weight_oneof {
google.protobuf.FloatValue override_weight = 3 [deprecated=true];
google.protobuf.DoubleValue double_override_weight = 5;
}
}
My question is, lets assume I have old messages who were compiled by the previous protobuff message compiler for the old message, would I be able to parse them as the new message?
The documentation is very vague about this:
"Move optional fields into or out of a oneof: You may lose some of your information (some fields will be cleared) after the message is serialized and parsed. However, you can safely move a single field into a new oneof and may be able to move multiple fields if it is known that only one is ever set."
Has anyone tried this before? what is the best practice for this situation?
As far as I know fields in an oneof are just serialize using their tag number. The serialized data does not indicate if a field is part of an oneof. This is all handled by the serializer and deserializer. So as long as the tag numbers do not conflict it can be assumed that it will work in both directions, old messages to a new serializer and new messages to an old serializer.
You could test this using an online protobuf deserializer.
Verification:
The code does indeed produce the same byte strings. Below you will find the message definitions and python code I used. The python code will output a byte string you can copy and use in the decoder of Marc Gravell.
syntax = "proto3";
message MessageA {
int64 id = 1;
float weight = 2;
float override_weight = 3;
}
message MessageB {
int64 id = 1;
oneof weight_oneof {
float weight = 2 [deprecated=true];
double double_weight = 4;
}
oneof override_weight_oneof {
float override_weight = 3 [deprecated=true];
double double_override_weight = 5;
}
}
import Example_pb2
# Set some data in the original message
msgA = Example_pb2.MessageA()
msgA.id = 1234
msgA.weight = 3.21
msgA.override_weight = 5.43
# Output the serialized bytes in a pretty format
str = 'msgA = '
for x in msgA.SerializeToString():
str += "{:02x} ".format(x)
print(str)
# Next set the original fields in the new message
msgB = Example_pb2.MessageB()
msgB.id = 1234
msgB.weight = 3.21
msgB.override_weight = 5.43
# Output the serialized bytes in a pretty format
str = 'msgB 1 = '
for x in msgB.SerializeToString():
str += "{:02x} ".format(x)
print(str)
# And finally set the new fields in msgB
msgB.double_weight = 3.21
msgB.double_override_weight = 5.43
# Output the serialized bytes in a pretty format
str = 'msgB 2 = '
for x in msgB.SerializeToString():
str += "{:02x} ".format(x)
print(str)
The output of the python script was:
msgA = 08 d2 09 15 a4 70 4d 40 1d 8f c2 ad 40
msgB 1 = 08 d2 09 15 a4 70 4d 40 1d 8f c2 ad 40
msgB 2 = 08 d2 09 21 ae 47 e1 7a 14 ae 09 40 29 b8 1e 85 eb 51 b8 15 40
As you can see message A and message B yield the same byte string when setting the original fields. Only when you set the new fields you get a different string.
I am trying to convert length message to ascii.
My length message is like
var ll = "0170";
In node js , is there some kind of function which converts into ascii?
Please help?
Here's a simple function(ES6) which converts a string into ASCII characters using charCodeAt()
const toAscii = (string) => string.split('').map(char=>char.charCodeAt(0)).join(" ")
console.log(toAscii("Hello, World"))
Output:
-> 72 101 108 108 111 44 32 87 111 114 108 100
You could create a prototype function aswell. There are many solutions :)
you can't have an ascii code for a whole string.
An ascii code is an integer value for a character, not a string. Then for your string "0170" you will get 4 ascii codes
you can display these ascii codes like this
var str = "0170";
for (var i = 0, len = str.length; i < len; i++) {
console.log(str[i].charCodeAt());
}
Ouput : 48 49 55 48
use charCodeAt() function to covert asscii format.
var ll = "0170";
function ascii (a) { return a.charCodeAt(); }
console.log(ascii(ll[0]),ascii(ll[1]), ascii(ll[2]), ascii(ll[3]) )
result:
48 49 55 48