I trying to read SD card image from arduino (20KB - JPEG -using SD library) and transfer through Xbee (series 2) Due to limitation on xbee, have to break to 60 bytes and send until the complete file send. I think, the image stored in ASCII character.
void setup() {
Serial.begin(115200);
if (!SD.begin()) {
Serial.println("begin failed");
return;
}
file = SD.open("PIC00.JPG");
}
void loop() {
Serial.flush();
char buf[64];
if(file) {
while (file.position() < file.size())
{
while (file.read(buf, sizeof(buf)) == sizeof(buf)) // read chunk of 64bytes
{
Serial.write(buf); // Send to xbee via serial
delay(50);
}
}
file.close();
} }
But this method, i can not see complete image transfer at Serial Write. After a while, i came to know the start of image is Y (ascii chracter) and U (end character). I can see only end start character Y can not see the proper end character.
Please advise...trying hard solve this issue. Big Thanks...
The JPEG is actually binary data. To send it, use the version of Serial.write() that includes a length parameter for the number of bytes to send. Otherwise, it thinks you're trying to send a null-terminated string.
(Declare bytesread as a byte at the top of your function.)
while ((bytesread = file.read(buf, sizeof(buf))) > 0)
{
Serial.write(buf, bytesread); // Send to xbee via serial
delay(50);
}
Also note that the delay might not be sufficient -- you should really be using a serial port with hardware flow control (monitoring /CTS from the XBee module) so you know when it's clear to send data to it.
Related
I'm constantly sending structs of int64 via Pyserial with:
with serial.Serial(port='COM4', baudrate=115200, timeout=.1) as arduino:
value = write_read(struct.pack(">q", int_array[1][i])) #this sends signed int.64 in bytes
print(value)
the struct.pack has this shape, for example:
b'\xff\xff\xff\xff\xff\xff\xff\xef'
and the function write_read consists of:
def write_read(x):
arduino.write((x))
data = arduino.readline()
#the idea is to receive an ACK from the Arduino after 8 bytes (the full
#number)
return data
The code I'm trying to develop in arduino is the following:
void loop() {
// send data only when you receive data:
if (Serial.available() \> 0) {
// read the incoming byte:
incomingByte = Serial.read();
//read 8 bytes and create the result
r= function_to_read_8_last_bytes // or similar
// say what you got:
Serial.print("I received: ");
Serial.printlesultn(r, DEC);
Serial.write("ACK");
}
}
I'm very curious how I could do a robust "read 8 bytes" function.
Should I add some especial character in the Python part to indentify when it ends one value?
Thanks! I'll appreciate any help :)
Given the discussion in the comments, it's hard to receive a stream of bytes and be sure that the receiver is completely synchronized. However let's make some assumptions to ease the problem:
The serial buffer is empty when you connect your laptop to Arduino. This ensures you won't receive spurious data with no meaning. I had this problem happens a lot when the serial connection was ended abruptly by any cause.
You are not constantly sending bytes, Arduino has time to process them until the start of the new sequence.
You only send this data, so there is no need to create a higher level protocol on top of it. Bare in mind that the serial communication is almost just an hardware stack, you receive bytes with no headers.
For assumption 1 you can write a simple piece of code to consume all the spurious bytes in the serial buffer as soon as your main starts from Arudino, so this will be done everytime you connect the serial (as this is also where the power supply comes from). Something like this:
void serialFlush(){
while(Serial.available() > 0) {
char t = Serial.read();
}
}
You can send a "READY" signal back to the Python interface, so that the program knows you are ready to receive data.
Going on with the solution you can implement an easy CRC in python, an additional byte which contains a XOR of all the previous bytes, and you check that in Arduino upon reception complete.
def xor_reduce_long_int(li):
res = 0;
for i in range(8):
mask = (0xFF)<<(i*8)
print(hex(mask))
masked = (li&mask)>>(i*8)
res ^= masked
return res
with serial.Serial(port='COM4', baudrate=115200, timeout=.1) as arduino:
crc=xor_reduce_long_int(int_array[1][i])
value = write_read(struct.pack(">qc", int_array[1][i],crc)) #this sends signed int.64 in bytes
print(value)
And with Arduino I would read 8 bytes when they are available and put them into an unsigned char buffer. I would then define a union that alias such buffer to interpret it as long long int.
typedef struct long_int_CRC
{
union
{
unsigned char bytes[8];
long int data;
};
unsigned char CRC;
}data_T;
// .. Later in main
data_T = received_data;
int received_bytes=0
unsigned char my_CRC = 0;
unsigned char rec_byte= 0;
while( received_bytes < 8 )
{
if(Serial.available() )
{
// Get the byte
rec_byte = Serial.read()
// Store the byte and calc CRC
received_data.bytes[received_bytes] = rec_byte;
my_CRC ^= rec_byte;
// Increment counter for next byte
received_bytes++;
}
}
// Reception complete, check CRC
unsigned char rec_CRC;
if(Serial.available() )
{
rec_CRC = Serial.read()
}
if( my_CRC != rec_CRC )
{
// Something was wrong!
}
// Now access your data as a long int
Serial.print("I received: ");
Serial.printlesultn(received_data.data, DEC);
Serial.write("ACK");
In this code i am taking the TID data(20bytes of 160bits) in the form of array according to the sparkfun(manufacture) documentation and RFID tag detection code and its working correctly and getting the output of RFID tags.
Now I just need your guidance that how can i stop displaying RFID tag ID which is already displayed on serial monitor of arduino. What should i have to do!
Arduino code:
/*Reading multiple RFID tags, simultaneously!
TIDs are 20 bytes, 160 bits*/
#include <SoftwareSerial.h> //Used for transmitting
SoftwareSerial softSerial(2, 3); //RX, TX
#include "SparkFun_UHF_RFID_Reader.h" //Library for controlling the M6E Nano module
RFID nano; //Create instance
void setup()
{
Serial.begin(115200);
while (!Serial);
Serial.println();
Serial.println("Initializing...");
if (setupNano(38400) == false) //Configure nano to run at 38400bps
{
Serial.println("Module failed to respond. Please check wiring.");
while (1); //Freeze!
}
nano.setRegion(REGION_NORTHAMERICA); //Set to North America
nano.setReadPower(1000); //10.00 dBm.
nano.enableDebugging(); //Turns on commands sent to and heard from RFID module
}
void loop()
{
/*Serial.println(F("Get one tag near the reader. Press a key to read unique tag ID."));
while (!Serial.available()); //Wait for user to send a character*/
Serial.read(); //Throw away the user's character
byte response;
byte myTID[20]; //TIDs are 20 bytes
byte tidLength = sizeof(myTID);
//Read unique ID of tag
response = nano.readTID(myTID, tidLength);
if (response == RESPONSE_SUCCESS)
{
Serial.println("TID read!");
Serial.print("TID: [");
for(byte x = 0 ; x < tidLength ; x++)
{
if(myTID[x] < 0x10) Serial.print("0");
Serial.print(myTID[x], HEX);
Serial.print(" ");
}
Serial.println("]");
}
else
Serial.println("Failed read");
}
//Gracefully handles a reader that is already configured and already reading continuously
//Because Stream does not have a .begin() we have to do this outside the library
boolean setupNano(long baudRate)
{
nano.begin(softSerial); //Tell the library to communicate over software serial port
softSerial.begin(baudRate); //For this test, assume module is already at our desired baud rate
while(!softSerial); //Wait for port to open
while(softSerial.available()) softSerial.read();
nano.getVersion();
if (nano.msg[0] == ERROR_WRONG_OPCODE_RESPONSE)
{
//This happens if the baud rate is correct but the module is doing a ccontinuous read
nano.stopReading();
Serial.println(F("Module continuously reading. Asking it to stop..."));
delay(1500);
}
else
{
//The module did not respond so assume it's just been powered on and communicating at 115200bps
softSerial.begin(115200); //Start software serial at 115200
nano.setBaud(baudRate); //Tell the module to go to the chosen baud rate. Ignore the response msg
softSerial.begin(baudRate); //Start the software serial port, this time at user's chosen baud rate
}
//Test the connection
nano.getVersion();
if (nano.msg[0] != ALL_GOOD) return (false); //Something is not right
//The M6E has these settings no matter what
nano.setTagProtocol(); //Set protocol to GEN2
nano.setAntennaPort(); //Set TX/RX antenna ports to 1
return (true); //We are ready to rock
}
That is what you should do in your application program.
The basic specifications of the RFID reader and RFID tag are to notify all tags within the reading range when reading is requested.
Please incorporate the following procedures / functions into the application.
The tag data notified from the RFID reader is stored for each reading.
By the next reading, the tag data notified this time is compared with previously notified data.
Tag data that has already been received is not displayed.
Please decide the interval and the number of times to keep record of tag data and compare it according to your specifications and requirements.
In the case of tags conforming to ISO/IEC 18000-63, duplication notification can not be made within a certain period by specifying a parameter called S flag at the time of reading request.
However, since the detailed behavior depends on the specifications of individual tags and the operating environment, use of the S flag is not recommended.
I have the following code (I'm using Arduino IDE and a NodeMCU with a MAX3232):
#include <SoftwareSerial.h>
SoftwareSerial RS232Serial(D1, D2); // RX | TX
void setup() {
Serial.begin(9600);
while (!Serial);
RS232Serial.begin(9600);
while (!RS232Serial);
}
void loop() {
Serial.println("Sending msg...");
char msg[] = {0x7E, 0x00, 0x78, 0xF0, 0x7E};
RS232Serial.write(msg, sizeof(msg));
Serial.println("Waiting incomming message:");
while(RS232Serial.available() <= 0) {
delay(1);
}
while(RS232Serial.available() > 0) {
Serial.print(RS232Serial.read(), HEX);
}
Serial.println("");
Serial.println("------------ END -----------");
}
I'm using Docklight to test the communication. So far I'm able to receive the HEX that the NodeMCU boards sends first char msg[] = {0x7E, 0x00, 0x78, 0xF0, 0x7E};. But I'm unable to receive the data properly from Docklight.
The HEX I'm trying to send from Docklight is 7E 00 00 70 15 7E. Debugging with serial monitor, sometimes I receive just 7E and sometimes 0FF, never the complete message. Baud rate, start/stop bits and parity are set to default.
What's wrong with my code?
One reason for not working as expected is:
You are processing the answer as soon as one byte has appeared in the receive buffer.
There is a related example in the Docklight Application Note Arduino Serial Communication - check the code listing on page 5. It makes use of the Arduino SerialEvent() function to collect the incoming telegram byte-per-byte. Only after receiving the end of telegram mark (here: a line feed "\n" character), it sets a flag that tells the code in the main loop() to do something with the accumulated data telegram.
The SerialEvent approach used in the Docklight exampleis not a must. You can solve this inside loop() alone, too. But you certainly need to change the
while(RS232Serial.available() <= 0) {
...
while(RS232Serial.available() > 0) {
parts to something that will wait until a full telegram has been received (or a timeout has occurred).
Now what irritates me still is that you write you sometimes receive "0FF" even though you never send it from Docklight. This could indicate still a second problem on the actual RS232 communication, but it's hard to guess without extra information.
But re-working the telegram receiving part as described above should already make things much clearer and then the source of the "0FF" is probably more obvious.
while(RS232Serial.available() <= 0) {
delay(1);
}
You are only waiting for the serial buffer to have at least 1 byte, but you are not guaranteed that your full message (6 bytes) will be present, when you call RS232Serial.available().
You should wait for the serial buffer to accumulate at least 6 bytes, before you try to read them.
while(RS232Serial.available() < 6) {
delay(1);
}
They you can read the full buffer with:
while(RS232Serial.available() > 0) {
Serial.print(RS232Serial.read(), HEX);
}
or only 6 bytes with:
for (int i=0; i<6; i++) {
Serial.print(RS232Serial.read(), HEX);
}
I don't know about your 0FF, but Serial.print(RS232Serial.read(), HEX) doesn't zero pad the hex string and this could actually be 00 0F 0F or 00 FF.
You should print out the bytes with:
byte b = RS232Serial.read();
if (b < 16) Serial.print('0'); // zero pad
Serial.print(b, HEX);
Serial.print(' '); // add space after each byte
So i have my arduino and esp8266 wifi module. Everything is connected correctly and sending data to arduino lets me control connection via AT commands.
My skletch looks like this:
void setup()
{
Serial.begin(9600);
Serial1.begin(9600);
}
void loop()
{
if (Serial.available() > 0) {
char ch = Serial.read();
Serial1.print(ch);
}
if (Serial1.available() > 0) {
char ch = Serial1.read();
Serial.print(ch);
}
The code above lets me send commands and see response from esp. In spite of different response time and different answers I need to store response in variable when wifi module such a response creates. Unfortunatelly I cant do this because of Serial1.read() grabing only one char from Serial1.available() buffer instead of full buffer.
I tried approach like this:
if (Serial1.available() > 0) {
while (Serial1.available() > 0) {
char ch = Serial1.read();
Serial.print(ch);
response = response.concat(ch);
}
} else {
String response = "";
}
So as long ther eis something in a buffer it is sent to response variable that concatens last char with itself. And later it can be searched via indefOf command for "OK" marker or "ERROR". But that doesnt work as intended :( It for example may print my variable 8 times (dont know why).
I need full response from wifi module to analaze it for example to make the led on in my arduino board if proper command comes from wifi network, but also send some data if i press button on arduino to the network. Any ideas would be appreciated.
Kalreg.
Try this rather:
String response = ""; // No need to recreate the String each time no data is available
char ch; // No need to recreate the variable in a loop
while (Serial1.available() > 0) {
ch = Serial1.read();
response = response.concat(ch);
}
// Now do whatever you want with the string by first checking if it is empty or not. Then do something with it
Also remember to clear the buffer before you send a command like I suggested in your previous question: how to get AT response from ESP8266 connected to arduino
I'm trying to read variable streams of characters and process them on the Arduino once a certain string of bytes is read on the Arduino. I have a sample sketch like the following, but I can't figure out how to compare the "readString" to process something on the Arduino. I would like the Arduino to process "commands" such as {blink}, {open_valve}, {close_valve}, etc.
// Serial - read bytes into string variable for string
String readString;
// Arduino serial read - example
int incomingByte;
// flow_A LED
int led = 4;
void setup() {
Serial.begin(2400); // Open serial port and set Baud rate to 2400.
Serial.write("Power on test");
}
void loop() {
while (Serial.available()) {
delay(10);
if (Serial.available() > 0) {
char c = Serial.read(); // Gets one byte from serial buffer
readString += c; // Makes the string readString
}
}
if (readString.length() > 0) {
Serial.println( readString); // See what was received
}
if (readString == '{blink_Flow_A}') {
digitalWrite(led, HIGH); // Turn the LED on (HIGH is the voltage level).
delay(1000); // Wait for one second.
digitalWrite(led, LOW); // Turn the LED off by making the voltage LOW.
delay(1000); // Wait for a second.
}
Some definitions first:
SOP = Start Of Packet (in your case, an opening brace)
EOP = End Of Packet (in your case, a closing brace)
PAYLOAD = the characters between SOP and EOP
PACKET = SOP + PAYLOAD + EOP
Example:
PACKET= {Abc}
SOP = {
EOP = }
PAYLOAD = Abc
Your code should process one character at a time, and should be structured as a state machine.
When the code starts, the parser state is "I'm waiting for the SOP character". While in this state, you throw away every character you receive unless it's equal to SOP.
When you find you received a SOP char, you change the parser state to "I'm receiving the payload". You store every character from now on into a buffer, until you either see an EOP character or exhaust the buffer (more on this in a moment). If you see the EOP char, you "close" the buffer by appending a NULL character (i.e. 0x00) so that it becomes a standard NULL-terminated C-string, and you can work on it with the standard functions (strcmp, strstr, strchr, etc.).
At this point you pass the buffer to a "process()" function, which executes the operation specified by the payload (1)
You have to specify the maximum length of a packet, and size the receive buffer accordingly. You also have to keep track of the current payload length during the "payload receive" state, so you don't accidentally try to store more payload bytes into the temporary buffer than it can hold (otherwise you get memory corruption).
If you fill the receive buffer without seeing an EOP character, then that packet is either malformed (too long) or a transmission error changed the EOP character into something else. In either case you should discard the buffer contents and go back to "Waiting for SOP" state.
Depending on the protocol design, you could send an error code to the PC so the person typing at the terminal or the software on that side knows the last command it sent was invalid or not received correctly.
Finally, the blink code in you snipped should be replaced by non-blocking "blink-without-delay"-style code (look at the example that come with the Arduino IDE).
(1) Example of a "process" function:
void process(char* cmd) {
if (strcmp(cmd, "open_valve") == 0) {
open_valve();
}
else if (strcmp(cmd, "close_valve") == 0) {
close_valve();
}
else {
print_error("Unrecognized command.");
}
}
It seems you are comparing the string in this statement:
if( readString == '{blink_Flow_A}' )
So I don't get your question re :
but I can't figure out how to compare the "readString" to process something
Are you really asking:
How do I extract the commands from an incoming stream of characters?
If that is the case then treat each command as a "packet". The packet is enclosed in brackets: {}. Knowing that the {} brackets are start and end of a packet, it is easy to write a routine to get at the command in the packet.
Once the command is extracted just go through a if-then-else statement to do what each command is supposed to do.
If I totally misunderstood your question I apologize :)
EDIT:
see http://arduino.cc/en/Tutorial/StringComparisonOperators
if( readString == "{blink_Flow_A}" ) should be correct syntax.
Since you have a statement
Serial.println( readString);
you should see the string received.