I'm new to the PSoC board and I'm trying to read the x,y,z values from a Digital Compass but I'm having a problem in beginning the Transmission with the compass itself.
I found some Arduino tutorial online here but since PSoC doesn't have the library I can't duplicate the code.
Also I was reading the HMC5883L datasheet here and I'm suppose to write bytes to the compass and obtain the values but I was unable to receive anything. All the values I received are zero which might be caused by reading values from wrong address.
Hoping for your answer soon.
PSoC is sorta tricky when you are first starting out with it. You need to read over the documentation carefully of both the device you want to talk to and the i2c module itself.
The datasheet for the device you linked states this on page 18:
All bus transactions begin with the master device issuing the start sequence followed by the slave address byte. The
address byte contains the slave address; the upper 7 bits (bits7-1), and the Least Significant bit (LSb). The LSb of the
address byte designates if the operation is a read (LSb=1) or a write (LSb=0). At the 9
th clock pulse, the receiving slave
device will issue the ACK (or NACK). Following these bus events, the master will send data bytes for a write operation, or
the slave will clock out data with a read operation. All bus transactions are terminated with the master issuing a stop
sequence.
If you use the I2C_MasterWriteBuf function, it wraps all that stuff the HMC's datasheet states above. The start command, dealing with that ack, the data handling, etc. The only thing you need to specify is how to transmit it.
If you refer to PSoC's I2C module datasheet, the MasterWriteBuf function takes in the device address, a pointer to the data you want to send, how many bytes you want to send, and a "mode". It shows what the various transfer modes in the docs.
I2C_MODE_COMPLETE_XFER Perform complete transfer from Start to Stop.
I2C_MODE_REPEAT_START Send Repeat Start instead of Start.
I2C_MODE_NO_STOP Execute transfer without a Stop
The MODE_COMPLETE_XFRE transfer will send the start and stop command for you if I'm not mistaken.
You can "bit-bang" this also if you want but calling directly on the I2C_MasterSendStart, WriteByte, SendStop, etc. But it's just easier to call on their writebuf functions.
Pretty much you need to write your code like follows:
// fill in your data or pass in the buffer of data you want to write
// if this is contained in a function call. I'm basing this off of HMC's docs
uint8 writeBuffer[3];
uint8 readBuffer[6];
writeBuffer[0] = 0x3C;
writeBuffer[1] = 0x00;
writeBuffer[2] = 0x70;
I2C_MasterWriteBuf(HMC_SLAVE_ADDRESS, &writeBuffer, 3, I2C_MODE_COMPLETE_XFER);
while((I2C_MasterStatus() & I2C_MSTAT_WR_CMPLT) == 0u)
{
// wait for operation to finish
}
writeBuffer[1] = 0x01;
writeBuffer[2] = 0xA0;
I2C_MasterWriteBuf(HMC_SLAVE_ADDRESS, &writeBuffer, 3, I2C_MODE_COMPLETE_XFER);
// wait for operation to finish
writeBuffer[1] = 0x02;
writeBuffer[2] = 0x00;
I2C_MasterWriteBuf(HMC_SLAVE_ADDRESS, &writeBuffer, 3, I2C_MODE_COMPLETE_XFER);
// wait for operation to finish
CyDelay(6); // docs state 6ms delay before you can start looping around to read
for(;;)
{
writeBuffer[0] = 0x3D;
writeBuffer[1] = 0x06;
I2C_MasterWriteBuf(HMC_SLAVE_ADDRESS, &writeBuffer, 2, I2C_MODE_COMPLETE_XFER);
// wait for operation to finish
// Docs don't state any different sort of bus transactions for reads.
// I'm assuming it'll be the same as a write
I2C_MasterReadBuf(HMC_SLAVE_ADDRESS, readBuffer, 6, I2C_MODE_COMPLETE_XFER);
// wait for operation to finish, wait on I2C_MSTAT_RD_CMPLT instead of WR_COMPLT
// You should have something in readBuffer to work with
CyDelay(67); // docs state to wait 67ms before reading again
}
I just sorta wrote that off the top of my head. I have no idea if that'll work or not, but I think that should be a good place to start and try. They have I2C example projects to look at also I think.
Another thing to look at so the WriteBuf function doesn't just seem like some magical command, if you right-click on the MasterWriteBuf function and click on "Find Definition" (after you build the project) it'll show you what it's doing.
Following are the samples for I2C read and write operation on PSoC,
simple Write operation:
//Dumpy data values to write
uint8 writebuffer[3]
writebuffer[0] = 0x23
writebuffer[1] = 0xEF
writebuffer[2] = 0x0F
uint8 I2C_MasterWrite(uint8 slaveAddr, uint8 nbytes)
{
uint8 volatile status;
status = I2C_MasterClearStatus();
if(!(status & I2C_MSTAT_ERR_XFER))
{
status = I2C_MasterWriteBuf(slaveAddr, (uint8 *)&writebuffer, nbytes, I2C_MODE_COMPLETE_XFER);
if(status == I2C_MSTR_NO_ERROR)
{
/* wait for write complete and no error */
do
{
status = I2C_MasterStatus();
} while((status & (I2C_MSTAT_WR_CMPLT | I2C_MSTAT_ERR_XFER)) == 0u);
}
else
{
/* translate from I2CM_MasterWriteBuf() error output to
* I2C_MasterStatus() error output */
status = I2C_MSTAT_ERR_XFER;
}
}
return status;
}
Read Operation:
void I2C_MasterRead(uint8 slaveaddress, uint8 nbytes)
{
uint8 volatile status;
status = I2C_MasterClearStatus();
if(!(status & I2C_MSTAT_ERR_XFER))
{
/* Then do the read */
status = I2C_MasterClearStatus();
if(!(status & I2C_MSTAT_ERR_XFER))
{
status = I2C_MasterReadBuf(slaveaddress,
(uint8 *)&(readbuffer),
nbytes, I2C_MODE_COMPLETE_XFER);
if(status == I2C_MSTR_NO_ERROR)
{
/* wait for reading complete and no error */
do
{
status = I2C_MasterStatus();
} while((status & (I2C_MSTAT_RD_CMPLT | I2C_MSTAT_ERR_XFER)) == 0u);
if(!(status & I2C_MSTAT_ERR_XFER))
{
/* Decrement all RW bytes in the EZI2C buffer, by different values */
for(uint8 i = 0u; i < nbytes; i++)
{
readbuffer[i] -= (i + 1);
}
}
}
else
{
/* translate from I2C_MasterReadBuf() error output to
* I2C_MasterStatus() error output */
status = I2C_MSTAT_ERR_XFER;
}
}
}
if(status & I2C_MSTAT_ERR_XFER)
{
/* add error handler code here */
}
}
Related
I want to read a String in Arduino from the keyboard outside of the loop() method.
I have the following method:
void readFromKeyboard(byte arrayAddress[])
{
int count = 0, i = 0;
while ((count = Serial.available()) == 0);
while (i<count)
{
arrayAddress[i++] = Serial.read();
}
}
In the loop() method I am calling it like:
readFromKeyboard(userInput);
where userInput is a byte[];
The problem is that when I input more than one characters it read the 1st character initially and it call the readFromKeyboard again an then reads the rest.
Example; if I input "asdf":
--the 1st time it will do ==> userInput = "a"
--the 2nd time it will do ==> userInput = "sdf"
I have tryed many things but the same happens again and again...
Any suggestions??
So that's what worked:
In the loop():
while(Serial.available() == 0);
delay(100);
readInputFlag = readFromKeyboard(userInput);`
And in the readFromKeyboard method:
void readFromKeyboard(byte arrayAddress[])
{
int i = 0;
while (Serial.available() > 0)
{
arrayAddress[i++] = Serial.read();
}
}
This delay, in the loop method, somehow makes the Serial get the whole string instead of just the first letter.
I know you got it working, but I wanted to show you something that I use to deal with this issue. This is a two-tiered delay system for catching bytes that come in a bit late for whatever reason. It's designed to minimize the delay needed to accomplish that task.
int received_length = 0;
byte serial_incoming_buffer[200];
while(Serial.available()) {
serial_incoming_buffer[received_length++] = Serial.read();
if(!Serial.available()) {
delay(3);
if(!Serial.available()) {
delay(20);
}
}
}
Sometimes the Arduino falls behind in picking up serial from the sender and sometimes it grabs serial too fast. Sometimes the sender lags a little bit. This code will wait 3 ms for more bytes, and if they come in it goes back to receiving as many as are available having only had that very brief delay. This repeats as necessary, then when 3 ms goes by without anything being available, it waits a bit longer (20 ms here) for more bytes. If nothing comes in after the long delay, then the transmission is most likely done and you can safely move on.
I recommend tweaking the delays based on your baud rate.
I have one Arduino with 4 Pots. The other Arduino receives these 4 values via i2c and prints them on a Display. The problem is that I don't know how to send these 4 values that the Slave is able to know which value belongs to which Pot.
Slave Code:
#include <Wire.h>
#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
void setup()
{
Wire.begin(5);
Wire.onReceive(receiveEvent);
Serial.begin(9600);
lcd.begin(16,2);
}
void loop()
{
}
void receiveEvent(int)
{
while(Wire.available())
{
//How to create this part? How does the Slave know which value belongs to which pot?
}
}
Master Code:
#include <Wire.h>
void setup()
{
Serial.begin(9600);
Wire.begin();
delay(2000);
}
void loop()
{
int sensor1 = analogRead(A1);
Wire.beginTransmission(5);
Wire.write(sensor1);
Serial.print(sensor1);
Wire.endTransmission();
delay(100);
int sensor2 = analogRead(A2);
Wire.beginTransmission(5);
Wire.write(sensor2);
Serial.print(sensor2);
Wire.endTransmission();
delay(500);
}
Ahh what we have here is a basic question on how to design I2C communication. Unfortunately Examples for I2C master and slave included in Arduino IDE are IMO too limited to provide clear guidance on this matter.
First of all in your examples the master and slaves roles are exchanged and should be switched. Slave should read values from analog inputs and master should request them. Why? Because it's master which should decide when to request values and properly decode the request. Slave should provide proper answer to a given request eliminating the problem of data interpretation.
I2C communication is based on requestFunction-(wait)-requestResponse sequence controlled by the master.
Plese refer to the range finder example on arduino page. In a nutshell:
First: master requests a function to measure distance:
// step 3: instruct sensor to return a particular echo reading
Wire.beginTransmission(112); // transmit to device #112
Wire.write(byte(0x02)); // sets register pointer to echo #1 register (0x02)
Wire.endTransmission(); // stop transmitting
(sometimes slaves need some time e.g. 10 - 50 ms to process requests but in the example I'm refering to master doesn't delay read)
Second: master requests response:
// step 4: request reading from sensor
Wire.requestFrom(112, 2); // request 2 bytes from slave device #112
Third: master tries to read and analyze response.
You should design reliable I2C communication in a similar way.
Here is how I do it; you can follow my pattern and get extensible slave implementation which will support one function: read analog inputs but can be easily extended by adding additional function codes and required processing implementation to the slave main loop
Initial remarks
some kind of a simple protocol is needed to control slave - e.g. it should support requesting functions. Supporting functions requests is not absolutely needed in such simmple scenario as reading four analog inputs but what I'm describing is a more general pattern you may use in other projects.
Slave should not perform any additional actions (like reading inputs) on request response as I2C communication may break (due to delays) and you will get partial responses etc. This is very important requirement which affect the slave design.
response (and also request if needed) can contain CRC as if master waits not long enough it may get empty response. If nobody else is going to use your code such countermeasures are not needed and will not be described here. Other important thing is Wire library buffer limitation which is 32 bytes and implementing CRC checksum without modifying the buffer length limits the available data length by two bytes (if crc16 is used).
slave:
#include <WSWire.h> // look on the web for an improved wire library which improves reliability by performing re-init on lockups
// >> put this into a header file you include at the beginning for better clarity
enum {
I2C_CMD_GET_ANALOGS = 1
};
enum {
I2C_MSG_ARGS_MAX = 32,
I2C_RESP_LEN_MAX = 32
};
#define I2C_ADDR 0
#define TWI_FREQ_SETTING 400000L // 400KHz for I2C
#define CPU_FREQ 16000000L // 16MHz
extern const byte supportedI2Ccmd[] = {
1
};
// << put this into a header file you include at the beginning for better clarity
int argsCnt = 0; // how many arguments were passed with given command
int requestedCmd = 0; // which command was requested (if any)
byte i2cArgs[I2C_MSG_ARGS_MAX]; // array to store args received from master
int i2cArgsLen = 0; // how many args passed by master to given command
uint8_t i2cResponse[I2C_RESP_LEN_MAX]; // array to store response
int i2cResponseLen = 0; // response length
void setup()
{
// >> starting i2c
TWBR = ((CPU_FREQ / TWI_FREQ_SETTING) - 16) / 2;
Wire.begin(I2C_ADDR); // join i2c bus
Wire.onRequest(requestEvent); // register event
Wire.onReceive(receiveEvent);
// << starting i2c
}
void loop()
{
if(requestedCmd == I2C_CMD_GET_ANALOGS){
// read inputs and save to response array; example (not tested) below
i2cResponseLen = 0;
// analog readings should be averaged and not read one-by-one to reduce noise which is not done in this example
i2cResponseLen++;
i2cResponse[i2cResponseLen -1] = analogRead(A0);
i2cResponseLen++;
i2cResponse[i2cResponseLen -1] = analogRead(A1);
i2cResponseLen++;
i2cResponse[i2cResponseLen -1] = analogRead(A2);
i2cResponseLen++;
i2cResponse[i2cResponseLen -1] = analogRead(A3);
// now slave is ready to send back four bytes each holding analog reading from a specific analog input; you can improve robustness of the protocol by including e.g. crc16 at the end or instead of returning just 4 bytes return 8 where odd bytes indicate analog input indexes and even bytes their values; change master implementation accordingly
requestedCmd = 0; // set requestd cmd to 0 disabling processing in next loop
}
else if (requestedCmd != 0){
// log the requested function is unsupported (e.g. by writing to serial port or soft serial
requestedCmd = 0; // set requestd cmd to 0 disabling processing in next loop
}
}
// function that executes whenever data is requested by master
// this function is registered as an event, see setup()
void requestEvent(){
Wire.write(i2cResponse, i2cResponseLen);
}
// function that executes when master sends data (begin-end transmission)
// this function is registered as an event, see setup()
void receiveEvent(int howMany)
{
//digitalWrite(13,HIGH);
int cmdRcvd = -1;
int argIndex = -1;
argsCnt = 0;
if (Wire.available()){
cmdRcvd = Wire.read(); // receive first byte - command assumed
while(Wire.available()){ // receive rest of tramsmission from master assuming arguments to the command
if (argIndex < I2C_MSG_ARGS_MAX){
argIndex++;
i2cArgs[argIndex] = Wire.read();
}
else{
; // implement logging error: "too many arguments"
}
argsCnt = argIndex+1;
}
}
else{
// implement logging error: "empty request"
return;
}
// validating command is supported by slave
int fcnt = -1;
for (int i = 0; i < sizeof(supportedI2Ccmd); i++) {
if (supportedI2Ccmd[i] == cmdRcvd) {
fcnt = i;
}
}
if (fcnt<0){
// implement logging error: "command not supported"
return;
}
requestedCmd = cmdRcvd;
// now main loop code should pick up a command to execute and prepare required response when master waits before requesting response
}
master:
#include <WSWire.h>
#define I2C_REQ_DELAY_MS 2 // used for IO reads - from node's memory (fast)
#define I2C_REQ_LONG_DELAY_MS 5 //used for configuration etc.
#define TWI_FREQ_SETTING 400000L
#define CPU_FREQ 16000000L
enum {
I2C_CMD_GET_ANALOGS = 1
};
int i2cSlaveAddr = 0;
void setup(){
// joining i2c as a master
TWBR = ((CPU_FREQ / TWI_FREQ_SETTING) - 16) / 2;
Wire.begin();
}
void loop(){
//requesting analogs read:
Wire.beginTransmission(i2cSlaveAddr);
Wire.write((uint8_t)I2C_CMD_GET_ANALOGS);
Wire.endTransmission();
delay(I2C_REQ_DELAY_MS);
// master knows slave should return 4 bytes to the I2C_CMD_GET_ANALOGS command
int respVals[4];
Wire.requestFrom(i2cSlaveAddr, 4);
uint8_t respIoIndex = 0;
if(Wire.available())
for (byte r = 0; r < 4; r++)
if(Wire.available()){
respVals[respIoIndex] = (uint8_t)Wire.read();
respIoIndex++;
}
else{
// log or handle error: "missing read"; if you are not going to do so use r index instead of respIoIndex and delete respoIoIndex from this for loop
break;
}
// now the respVals array should contain analog values for each analog input in the same order as defined in slave (respVals[0] - A0, respVals[1] - A1 ...)
}
I hope my example will help. It's based on code working for weeks making 40 reads a second from multiple slaves however I have not compiled it to test the function you require.
Please use WSWire library as the Wire (at least as for Arduino 1.0.3) may occasionally freeze your master if for some reason slave will not respond to request.
EDIT: The WSWire lib requires external pull-up resistors for I2C unless you modify the source and enable internal pull-ups like Wire does.
EDIT: instead of creating i2c slave implementation you may try the EasyTransfer library. I haven't tried it but it may be easier to use it if sending four bytes is everything you need.
EDIT[12.2017]: There is a new player on the block - PJON - a library suited for easy multi-master communication ideal to exchange pot values (and much more). It's been around for some time but gained a substantial development speed in recent months. I'm partially involved in its development and switched all field-level and local buses I've used so far (I2C, MODBUS RTU) to PJON over single wire, hardware serial or RF.
Check out GitHub-I2CBus, I've done the exact same thing. Hope it can help
I have just downloaded the latest Arduino Library code from Github, and it's broken my MQTT client program. I'm using PubSubClient 1.91 on Arduino, and Mosquitto 1.1.2 (Build 2013-03-07) on Mac OSX. (I also tested against Mosquitto on Windows 7, same problem.)
The supplied Mosquitto clients work fine, (Mac over to Windows, Windows over to Mac) so it's some problem with what's coming from the Arduino end. A wireshark trace shows the Arduino client sending the following data packet:
10:15:ff:ff:4d:51:49:73:64:70:03:02:00:0f:00:07:41:72:64:75:69:6e:6f
And the Mosquitto broker shows:
New connection from 10.0.0.115
Socket read error on client (null), disconnecting.
Before I start to crawl through the MQTT spec, can anyone see anything wrong with the data packet being sent? It's got to be something to do with new Arduino library code...
* Update
Upon further investigation, it appears to be a code generation problem with avr-g++, although life experience tells me it will turn out not to be so. Here is a snippet of code from PubSubClient.cpp
boolean PubSubClient::connect(char *id, char *user, char *pass, char* willTopic, uint8_t willQos, uint8_t willRetain, char* willMessage) {
if (!connected()) {
int result = 0;
if (domain != NULL) {
result = _client->connect(this->domain, this->port);
} else {
result = _client->connect(this->ip, this->port);
}
if (result) {
nextMsgId = 1;
uint8_t d[9] = { 0x00, 0x06, 'M','Q','I','s','d','p',MQTTPROTOCOLVERSION};
// d[0] = 0;
// d[1] = 6;
Serial.print("d[0]="); Serial.println(d[0],HEX);
Now, the result of the Serial.print just above turns out to be 0xFF !!! So, the uint8_t array is not being initialised correctly. #knoleary Your pointer to the bad FF bytes lead me to this.
If I now uncomment the two lines above, and manually initialise the first 2 bytes to 0 and 6, all works fine, and my program communicates happily with Mosquitto.
I've looked at the generated code, but I'm not an Atmel expert.
Does anyone have any clue why this might be?
I'm compiling using the AVR-G++ toolset from Arduino 1.05, in Eclipse.
I'm going for a beer!
OK, I found it. It's a relatively subtle bug. Essentially, when the following line of source code is compiled;
uint8_t d[9] = { 0x00, 0x06, 'M','Q','I','s','d','p',MQTTPROTOCOLVERSION};
the 9 bytes get stored as a constant in the data section of the image. At runtime, a small loop copies the 9 bytes into the array (d[]) By looking at a combined Assembler / source listing, I could see where in the data section the 9 bytes were stored, and then print them out at regular intervals, until I found what was over-writing them. (A bit primitive, I know!)
It turns out the there's a bug in WiFi.cpp , the Arduino WiFi code. Here's the code:
uint8_t WiFiClient::connected() {
if (_sock == 255) {
return 0;
} else {
uint8_t s = status();
return !(s == LISTEN || s == CLOSED || s == FIN_WAIT_1 ||
s == FIN_WAIT_2 || s == TIME_WAIT ||
s == SYN_SENT || s== SYN_RCVD ||
(s == CLOSE_WAIT));
}
}
It turns out the the _sock variable is actually initialised like this:
WiFiClient::WiFiClient() : _sock(MAX_SOCK_NUM) {
}
and MAX_SOCK_NUM is 4, not 255. So, WiFiClient::status returned true, instead of false for an unused Socket.
This method was called by the MQTT Client like this:
boolean PubSubClient::connected() {
boolean rc;
if (_client == NULL ) {
rc = false;
} else {
rc = (int)_client->connected();
if (!rc) _client->stop();
}
return rc;
}
And, since the _client->connected() method erroneously returned true, the _client_stop() method was called. This resulted in a write to a non-existent socket array element, and so overwrote my string data.
#knolleary, I was wondering, is there any specific reason that your PubSubClient::connected() method does a disconnect? I use the ::connected method in a loop, to check that I'm still connected, and, of course it results in my getting a disconnect / reconnect each time round the loop. Any chance we could just make connected return true / false , and handle the disconnect in PuBSubClient::connect?
Nearly one and a half year later I ran into the same problem. Removing the
boolean PubSubClient::connected() {
int rc = (int)_client->connected();
if (!rc) _client->stop();
return rc;
}
the _client->stop() from the connected method of PubSubClient forehand fixed this problem for me. However, I'm not sure whether this is actually a solution or just a very dirty quick hack to localize the problem.
What have you done to fix this problem - your explanation of the problem above is fine however, I was not able to extract the solution easily ;-)
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.
I am currently in the process of making a Client and Server in the Unix/Windows environment but right now I am just working on the Unix side of it. One of the function we have to create for the program is similar to the list function in Unix which shows all files within a dir but we also have to show more information about the file such as its owner and creation date. Right now I am able to get all this information and print it to the client however we have to also add that once the program has printing 40 lines it waits for the client to push any key before it continues to print.
I have gotta the program to sort of do this but it will cause my client and server to become out of sync or at least the std out to become out of sync. This means that if i enter the command 'asdad' it should print invalid command but it won't print that message until i enter another command. I have added my list functions code below. I am open to suggestions how how to complete this requirement as the method I have chosen does not seem to be working out.
Thank-you in advance.
Server - Fork Function: This is called when the list command is enter. eg
fork_request(newsockfd, "list", buf);
int fork_request(int fd, char req[], char buf[])
{
#ifndef WIN
int pid = fork();
if (pid ==-1)
{
printf("Failed To Fork...\n");
return-1;
}
if (pid !=0)
{
wait(NULL);
return 10;
}
dup2(fd,1); //redirect standard output to the clients std output.
close(fd); //close the socket
execl(req, req, buf, NULL); //run the program
exit(1);
#else
#endif
}
Here is the function used to get all the info about a file in a dir
void longOutput(char str[])
{
char cwd[1024];
DIR *dip;
struct dirent *dit;
int total;
char temp[100];
struct stat FileAttrib;
struct tm *pTm;
int fileSize;
int lineTotal;
if(strcmp(str, "") == 0)
{
getcwd(cwd, sizeof(cwd));
}
else
{
strcpy (cwd, str);
}
if (cwd != NULL)
{
printf("\n Using Dir: %s\n", cwd);
dip = opendir(cwd);
if(dip != NULL)
{
while ((dit = readdir(dip)) != NULL)
{
printf("\n%s",dit->d_name);
stat(dit->d_name, &FileAttrib);
pTm = gmtime(&FileAttrib.st_ctime);
fileSize = FileAttrib.st_size;
printf("\nFile Size: %d Bytes", fileSize);
printf("\nFile created on: %.2i/%.2i/%.2i at %.2i:%.2i:%.2i GMT \n", (pTm->tm_mon + 1), pTm->tm_mday,(pTm->tm_year % 100),pTm->tm_hour,pTm->tm_min, pTm->tm_sec);;
lineTotal = lineTotal + 4;
if(lineTotal == 40)
{
printf("40 Lines: Waiting For Input!");
fflush(stdout);
gets(&temp);
}
}
printf("\n %d \n", lineTotal);
}
else
{
perror ("");
}
}
}
At here is the section of the client where i check that a ! was not found in the returned message. If there is it means that there were more lines to print.
if(strchr(command,'!') != NULL)
{
char temp[1000];
gets(&temp);
}
Sorry for the long post but if you need anything please just ask.
Although, I didn't see any TCP/IP code, I once had a similar problem when I wrote a server-client chat program in C++. In my case, the problem was that I didn't clearly define how messages were structured in my application. Once, I defined how my protocol was suppose to work--it was a lot easier to debug communication problems.
Maybe you should check how your program determines if a message is complete. In TCP, packets are guaranteed to arrive in order with no data loss, etc. Much like a conversation over a telephone. The only thing you have to be careful of is that it's possible to receive a message partially when you read the buffer for the socket. The only way you know to stop reading is when you determine a message is complete. This could be as simple as two '\n' characters or "\n\r".
If you are using UDP, then that is a completely different beast all together (i.e. messages can arrive out of order and can be lost in transit, et cetera).
Also, it looks like you are sending across strings and no binary data. If this is the case, then you don't have to worry about endianess.