Hello all,
I am having trouble getting HC-12 modules working for a project. I plan to use several HC-12's with PIR sensors to make a long range wireless motion alarm system. Each unit will just transmit a number giving it an ID and triggering an alarm at the receiving unit. I began asking Mark Hughes about my problems in an earlier post of his but this has expanded to the point I need to start a new post. I am using a sketch Mark wrote for the HC-12 that also enables the controller to send AT commands. I did a cut and paste of his sketch. I also deleted and started over with a new sketch a few times now.
I have several arduinos(uno, 2560, knockoff nano's) that I have tried to use. I have a few different HC-12's from two different knockoff companies. I also am running the proper driver for the knockoff boards and had to update avrdude on a couple in order for them to be seen by the IDE.
I have connected some of the boards to a PIR or a DHT sensor and those read on the serial monitor as they should. I also looked for some sketch already written that I could use to test this besides Marks' but have found nothing yet. I think his is perfect thought for what I am trying to figure out as I need something going in and out of each board. I have also played with baud rates just to rule that out and ended with everything set at 9600. I may be leaving out some important facts. If so, let me know and I will get it up asap.
The problem I am having is that when data is sent, it does not show up on the serial monitor on the receiving end. I first noticed when I would send the AT command and the HC-12 would not return an OK. I contacted Mark through another thread yesterday and he made a couple of suggestions. His first suggestion was to connect the two micro boards together without the HC-12's. I did as he suggested and connected the transmit to the receive and the receive to the transmit. I started out using an uno and a nano. I got nothing this way in the serial monitor. I did see the receive led flash when I hit the send key going both ways. Next I tried a pair of nano's. I got the same thing, no input in the serial monitor but the led did flash. At this point, I have no reason to think it is the HC-12. I am not a designer, but I can find my way around basic circuits. I am mostly a noob at writing code, though I understand what I read. Any help will be greatly appreciated.

Mitch

 

Do you think you can put some paragraph breaks in there? All of that is extremely difficult to read. Way too many details.

A simple schematic and your code would be a lot more useful than all of that.

And I am completely confused at what kind of micro controller your are using.

Do you have a scope?? If so, check to make certain you are sending data to th emicro then check if it is responding.

 

#include <SoftwareSerial.h>

const byte HC12RxdPin = 4; // "RXD" Pin on HC12
const byte HC12TxdPin = 5; // "TXD" Pin on HC12
const byte HC12SetPin = 6; // "SET" Pin on HC12

unsigned long timer = millis(); // Delay Timer

char SerialByteIn; // Temporary variable
char HC12ByteIn; // Temporary variable
String HC12ReadBuffer = ""; // Read/Write Buffer 1 for HC12
String SerialReadBuffer = ""; // Read/Write Buffer 2 for Serial
boolean SerialEnd = false; // Flag to indicate End of Serial String
boolean HC12End = false; // Flag to indiacte End of HC12 String
boolean commandMode = false; // Send AT commands

// Software Serial ports Rx and Tx are opposite the HC12 Rx and Tx
// Create Software Serial Port for HC12
SoftwareSerial HC12(HC12TxdPin, HC12RxdPin);

void setup() {

HC12ReadBuffer.reserve(64); // Reserve 64 bytes for Serial message input
SerialReadBuffer.reserve(64); // Reserve 64 bytes for HC12 message input

pinMode(HC12SetPin, OUTPUT); // Output High for Transparent / Low for Command
digitalWrite(HC12SetPin, HIGH); // Enter Transparent mode
delay(80); // 80 ms delay before operation per datasheet
Serial.begin(9600); // Open serial port to computer
HC12.begin(9600); // Open software serial port to HC12
}

void loop() {

while (HC12.available()) { // While Arduino's HC12 soft serial rx buffer has data
HC12ByteIn = HC12.read(); // Store each character from rx buffer in byteIn
HC12ReadBuffer += char(HC12ByteIn); // Write each character of byteIn to HC12ReadBuffer
if (HC12ByteIn == '\n') { // At the end of the line
HC12End = true; // Set HC12End flag to true
}
}

while (Serial.available()) { // If Arduino's computer rx buffer has data
SerialByteIn = Serial.read(); // Store each character in byteIn
SerialReadBuffer += char(SerialByteIn); // Write each character of byteIn to SerialReadBuffer
if (SerialByteIn == '\n') { // Check to see if at the end of the line
SerialEnd = true; // Set SerialEnd flag to indicate end of line
}
}

if (SerialEnd) { // Check to see if SerialEnd flag is true

if (SerialReadBuffer.startsWith("AT")) { // Has a command been sent from local computer
HC12.print(SerialReadBuffer); // Send local command to remote HC12 before changing settings
delay(100); //
digitalWrite(HC12SetPin, LOW); // Enter command mode
delay(100); // Allow chip time to enter command mode
Serial.print(SerialReadBuffer); // Echo command to serial
HC12.print(SerialReadBuffer); // Send command to local HC12
delay(500); // Wait 0.5s for a response
digitalWrite(HC12SetPin, HIGH); // Exit command / enter transparent mode
delay(100); // Delay before proceeding
} else {
HC12.print(SerialReadBuffer); // Transmit non-command message
}
SerialReadBuffer = ""; // Clear SerialReadBuffer
SerialEnd = false; // Reset serial end of line flag
}

if (HC12End) { // If HC12End flag is true
if (HC12ReadBuffer.startsWith("AT")) { // Check to see if a command is received from remote
digitalWrite(HC12SetPin, LOW); // Enter command mode
delay(100); // Delay before sending command
Serial.print(SerialReadBuffer); // Echo command to serial.
HC12.print(HC12ReadBuffer); // Write command to local HC12
delay(500); // Wait 0.5 s for reply
digitalWrite(HC12SetPin, HIGH); // Exit command / enter transparent mode
delay(100); // Delay before proceeding
HC12.println("Remote Command Executed"); // Acknowledge execution
} else {
Serial.print(HC12ReadBuffer); // Send message to screen
}
HC12ReadBuffer = ""; // Empty buffer
HC12End = false; // Reset flag
}
}

 

Do you have a scope?


I would start by simplifying your code. Forget about reading data on the Arduino. Just write a small program to open up the port then continually write some text to the port.

 

Spinnaker,
I am using multiple micros. Let's choose a nano for simplicity. I do have a scope and I did just check pins 4 and 5. They both have 5 volts( 4.63) with the sketch loaded. I mean to say, there is 5 volts present all the time. I see no change when I hit the send key. Nothing going out of the sending unit. Just a continuous 5 volts. I did notice though that only the RECEIVE LED lit on the SENDING unit as I pressed the send key. It was not the receiving board that lit. I may have got that screwed up when I noted it earlier. Now I'm not so sure of what I saw previously. Just now, I replaced the sketch with BLINK. The pins 4&5 are then 0 volts. Lastly I just took one of the nano's I was using for this experiment and put a DHT sensor on it, then loaded a DHT sketch. It works fine and everything prints out in the serial monitor. Must be something in my code? One more thing.....I have tried many sketches from different folks using the HC-12 in various capacities. So far, I haven't got any of them to work, not even the simple ones.

Mitch

 

MODERATOR please delete post #5.

TY

You can delete or edit your own posts

 

Spinnaker,
I am using multiple micros. Let's choose a nano for simplicity. I do have a scope and I did just check pins 4 and 5. They both have 5 volts( 4.63) with the sketch loaded. I mean to say, there is 5 volts present all the time. I see no change when I hit the send key. Nothing going out of the sending unit. Just a continuous 5 volts. I did notice though that only the RECEIVE LED lit on the SENDING unit as I pressed the send key. It was not the receiving board that lit. I may have got that screwed up when I noted it earlier. Now I'm not so sure of what I saw previously. Just now, I replaced the sketch with BLINK. The pins 4&5 are then 0 volts. Lastly I just took one of the nano's I was using for this experiment and put a DHT sensor on it, then loaded a DHT sketch. It works fine and everything prints out in the serial monitor. Must be something in my code? One more thing.....I have tried many sketches from different folks using the HC-12 in various capacities. So far, I haven't got any of them to work, not even the simple ones.

Mitch

Sorry you are way too confusing. You need to organize your thoughts before posting. Forget about the non relevant information. The DHT sensor and blink and all of that, has nothing to do with your current problem.


Is it two micros that are talking to one another?? Or ar you talking to one of two micros from a PC?

If you are sending data from a PC, start at the beginning. Please confirm that it is a PC sending the data and you are seeing data transmitted by the PC. If you can't see data being transmitted then there is something wrong with your terminal configuration.

 

Spinnaker,
I am using multiple micros. Let's choose a nano for simplicity. I do have a scope and I did just check pins 4 and 5. They both have 5 volts( 4.63) with the sketch loaded. I mean to say, there is 5 volts present all the time. I see no change when I hit the send key. Nothing going out of the sending unit. Just a continuous 5 volts. I did notice though that only the RECEIVE LED lit on the SENDING unit as I pressed the send key. It was not the receiving board that lit. I may have got that screwed up when I noted it earlier. Now I'm not so sure of what I saw previously. Just now, I replaced the sketch with BLINK. The pins 4&5 are then 0 volts. Lastly I just took one of the nano's I was using for this experiment and put a DHT sensor on it, then loaded a DHT sketch. It works fine and everything prints out in the serial monitor. Must be something in my code? One more thing.....I have tried many sketches from different folks using the HC-12 in various capacities. So far, I haven't got any of them to work, not even the simple ones.

Mitch

When you say "hit the send key" are you talking about typing something from your computer and sending it through serial communication into the nano? I don't see anything in your code polling for key presses, so I assume you're looking for input via USB.

Assuming I've understood that much right, that's why you're seeing the "receive" LED light up during that. The LED indicators tell you what's going on with the serial port, not the virtual software serial port that you've created for the HC12.

 

I think you need to draw a diagram about how you have everything connected together. I assume that you are talking about the serial monitor in the Arduino IDE. If this is so then do you realise that when you send characters out from the serial monitor that these will come out on the pin that is the ATMEGA328P receive pin. If we are talking about an Aduino UNO then the usb to serial conversion is done by the ATMEGA16U on the uno board. A send from the serial monitor would come out of the TX pin on the 16U which is connected to the RX pin on the 328P If you want to see data received by the HC12 on the serial monitor you need to do something to prevent the 328P's TX pin from shorting out the incomming data (To the UNO) (Which would be the pin marked TX as this is the receive as far as the 16U is conserned.). Unplugging the 328U is the simplest way to do this but you could also be running code on the 328u that made the 328p TX pin (Pin 3 PD1) an input so it would not short out the signal.

Les.

 

hi,
Are you sure that you have the correct frequency channel set at both ends ie: TX and RX.?
Also is your channel selection not being used by some other local transmitter, the HC12 can be received upto 1000 mtrs
I use the HC12 on a number of projects, one similar to what you are trying to do.

E

 

Try this code as is get that to working and then come back
and tell how that goes

/*  HC12 Send/Receive Example Program 2
    By Mark J. Hughes
    for AllAboutCircuits.com

    This code will automatically detect commands as sentences that begin
    with AT and both write them and broadcast them to remote receivers
    to be written.  Changing settings on a local transceiver will
    change settings on a remote receiver.

    Connect HC12 "RXD" pin to Arduino Digital Pin 4
    Connect HC12 "TXD" pin to Arduino Digital Pin 5
    Connect HC12 "Set" pin to Arduino Digital Pin 6

    Do not power HC12 via Arduino over USB.  Per the data sheet,
    power the HC12 with a supply of at least 100 mA with
    a 22 uF to 1000 uF reservoir capacitor and connect a 1N4007 diode in
    series with the positive supply line if the potential difference exceeds 4.5 V.

    Upload code to two Arduinos connected to two computers
    that are separated by at least several meters.

*/

#include <SoftwareSerial.h>

const byte HC12RxdPin = 4;                      // "RXD" Pin on HC12
const byte HC12TxdPin = 5;                      // "TXD" Pin on HC12
const byte HC12SetPin = 6;                      // "SET" Pin on HC12

unsigned long timer = millis();                 // Delay Timer

char SerialByteIn;                              // Temporary variable
char HC12ByteIn;                                // Temporary variable
String HC12ReadBuffer = "";                     // Read/Write Buffer 1 for HC12
String SerialReadBuffer = "";                   // Read/Write Buffer 2 for Serial
boolean SerialEnd = false;                      // Flag to indicate End of Serial String
boolean HC12End = false;                        // Flag to indiacte End of HC12 String
boolean commandMode = false;                    // Send AT commands

// Software Serial ports Rx and Tx are opposite the HC12 Rx and Tx
// Create Software Serial Port for HC12
SoftwareSerial HC12(HC12TxdPin, HC12RxdPin);

void setup() {

  HC12ReadBuffer.reserve(64);                   // Reserve 64 bytes for Serial message input
  SerialReadBuffer.reserve(64);                 // Reserve 64 bytes for HC12 message input

  pinMode(HC12SetPin, OUTPUT);                  // Output High for Transparent / Low for Command
  digitalWrite(HC12SetPin, HIGH);               // Enter Transparent mode
  delay(80);                                    // 80 ms delay before operation per datasheet
  Serial.begin(9600);                           // Open serial port to computer
  HC12.begin(9600);                             // Open software serial port to HC12
}

void loop() {

  while (HC12.available()) {                    // While Arduino's HC12 soft serial rx buffer has data
    HC12ByteIn = HC12.read();                   // Store each character from rx buffer in byteIn
    HC12ReadBuffer += char(HC12ByteIn);         // Write each character of byteIn to HC12ReadBuffer
    if (HC12ByteIn == '\n') {                   // At the end of the line
      HC12End = true;                           // Set HC12End flag to true
    }
  }

  while (Serial.available()) {                  // If Arduino's computer rx buffer has data
    SerialByteIn = Serial.read();               // Store each character in byteIn
    SerialReadBuffer += char(SerialByteIn);     // Write each character of byteIn to SerialReadBuffer
    if (SerialByteIn == '\n') {                 // Check to see if at the end of the line
      SerialEnd = true;                         // Set SerialEnd flag to indicate end of line
    }
  }

  if (SerialEnd) {                              // Check to see if SerialEnd flag is true

    if (SerialReadBuffer.startsWith("AT")) {    // Has a command been sent from local computer
      HC12.print(SerialReadBuffer);             // Send local command to remote HC12 before changing settings
      delay(100);                               //
      digitalWrite(HC12SetPin, LOW);            // Enter command mode
      delay(100);                               // Allow chip time to enter command mode
      Serial.print(SerialReadBuffer);           // Echo command to serial
      HC12.print(SerialReadBuffer);             // Send command to local HC12
      delay(500);                               // Wait 0.5s for a response
      digitalWrite(HC12SetPin, HIGH);           // Exit command / enter transparent mode
      delay(100);                               // Delay before proceeding
    } else {
      HC12.print(SerialReadBuffer);             // Transmit non-command message
    }
    SerialReadBuffer = "";                      // Clear SerialReadBuffer
    SerialEnd = false;                          // Reset serial end of line flag
  }

  if (HC12End) {                                // If HC12End flag is true
    if (HC12ReadBuffer.startsWith("AT")) {      // Check to see if a command is received from remote
      digitalWrite(HC12SetPin, LOW);            // Enter command mode
      delay(100);                               // Delay before sending command
      Serial.print(SerialReadBuffer);           // Echo command to serial.
      HC12.print(HC12ReadBuffer);               // Write command to local HC12
      delay(500);                               // Wait 0.5 s for reply
      digitalWrite(HC12SetPin, HIGH);           // Exit command / enter transparent mode
      delay(100);                               // Delay before proceeding
      HC12.println("Remote Command Executed");  // Acknowledge execution
    } else {
      Serial.print(HC12ReadBuffer);             // Send message to screen
    }
    HC12ReadBuffer = "";                        // Empty buffer
    HC12End = false;                            // Reset flag
  }
}

 

You have to type your AT commands your sending your code has nothing to send
so to get anything you have to send the needed commands.

 

Try this code as is get that to working and then come back
and tell how that goes

/*  HC12 Send/Receive Example Program 2
    By Mark J. Hughes
    for AllAboutCircuits.com

    This code will automatically detect commands as sentences that begin
    with AT and both write them and broadcast them to remote receivers
    to be written.  Changing settings on a local transceiver will
    change settings on a remote receiver.

    Connect HC12 "RXD" pin to Arduino Digital Pin 4
    Connect HC12 "TXD" pin to Arduino Digital Pin 5
    Connect HC12 "Set" pin to Arduino Digital Pin 6

    Do not power HC12 via Arduino over USB.  Per the data sheet,
    power the HC12 with a supply of at least 100 mA with
    a 22 uF to 1000 uF reservoir capacitor and connect a 1N4007 diode in
    series with the positive supply line if the potential difference exceeds 4.5 V.

    Upload code to two Arduinos connected to two computers
    that are separated by at least several meters.

*/

#include <SoftwareSerial.h>

const byte HC12RxdPin = 4;                      // "RXD" Pin on HC12
const byte HC12TxdPin = 5;                      // "TXD" Pin on HC12
const byte HC12SetPin = 6;                      // "SET" Pin on HC12

unsigned long timer = millis();                 // Delay Timer

char SerialByteIn;                              // Temporary variable
char HC12ByteIn;                                // Temporary variable
String HC12ReadBuffer = "";                     // Read/Write Buffer 1 for HC12
String SerialReadBuffer = "";                   // Read/Write Buffer 2 for Serial
boolean SerialEnd = false;                      // Flag to indicate End of Serial String
boolean HC12End = false;                        // Flag to indiacte End of HC12 String
boolean commandMode = false;                    // Send AT commands

// Software Serial ports Rx and Tx are opposite the HC12 Rx and Tx
// Create Software Serial Port for HC12
SoftwareSerial HC12(HC12TxdPin, HC12RxdPin);

void setup() {

  HC12ReadBuffer.reserve(64);                   // Reserve 64 bytes for Serial message input
  SerialReadBuffer.reserve(64);                 // Reserve 64 bytes for HC12 message input

  pinMode(HC12SetPin, OUTPUT);                  // Output High for Transparent / Low for Command
  digitalWrite(HC12SetPin, HIGH);               // Enter Transparent mode
  delay(80);                                    // 80 ms delay before operation per datasheet
  Serial.begin(9600);                           // Open serial port to computer
  HC12.begin(9600);                             // Open software serial port to HC12
}

void loop() {

  while (HC12.available()) {                    // While Arduino's HC12 soft serial rx buffer has data
    HC12ByteIn = HC12.read();                   // Store each character from rx buffer in byteIn
    HC12ReadBuffer += char(HC12ByteIn);         // Write each character of byteIn to HC12ReadBuffer
    if (HC12ByteIn == '\n') {                   // At the end of the line
      HC12End = true;                           // Set HC12End flag to true
    }
  }

  while (Serial.available()) {                  // If Arduino's computer rx buffer has data
    SerialByteIn = Serial.read();               // Store each character in byteIn
    SerialReadBuffer += char(SerialByteIn);     // Write each character of byteIn to SerialReadBuffer
    if (SerialByteIn == '\n') {                 // Check to see if at the end of the line
      SerialEnd = true;                         // Set SerialEnd flag to indicate end of line
    }
  }

  if (SerialEnd) {                              // Check to see if SerialEnd flag is true

    if (SerialReadBuffer.startsWith("AT")) {    // Has a command been sent from local computer
      HC12.print(SerialReadBuffer);             // Send local command to remote HC12 before changing settings
      delay(100);                               //
      digitalWrite(HC12SetPin, LOW);            // Enter command mode
      delay(100);                               // Allow chip time to enter command mode
      Serial.print(SerialReadBuffer);           // Echo command to serial
      HC12.print(SerialReadBuffer);             // Send command to local HC12
      delay(500);                               // Wait 0.5s for a response
      digitalWrite(HC12SetPin, HIGH);           // Exit command / enter transparent mode
      delay(100);                               // Delay before proceeding
    } else {
      HC12.print(SerialReadBuffer);             // Transmit non-command message
    }
    SerialReadBuffer = "";                      // Clear SerialReadBuffer
    SerialEnd = false;                          // Reset serial end of line flag
  }

  if (HC12End) {                                // If HC12End flag is true
    if (HC12ReadBuffer.startsWith("AT")) {      // Check to see if a command is received from remote
      digitalWrite(HC12SetPin, LOW);            // Enter command mode
      delay(100);                               // Delay before sending command
      Serial.print(SerialReadBuffer);           // Echo command to serial.
      HC12.print(HC12ReadBuffer);               // Write command to local HC12
      delay(500);                               // Wait 0.5 s for reply
      digitalWrite(HC12SetPin, HIGH);           // Exit command / enter transparent mode
      delay(100);                               // Delay before proceeding
      HC12.println("Remote Command Executed");  // Acknowledge execution
    } else {
      Serial.print(HC12ReadBuffer);             // Send message to screen
    }
    HC12ReadBuffer = "";                        // Empty buffer
    HC12End = false;                            // Reset flag
  }
}

Wow, I didn't realize how much I've come to rely on the standard formatting. The indentations make it so much easier to read. Thanks!

 

Spinnaker,
I am using multiple micros. Let's choose a nano for simplicity. I do have a scope and I did just check pins 4 and 5. They both have 5 volts( 4.63) with the sketch loaded. I mean to say, there is 5 volts present all the time. I see no change when I hit the send key. Nothing going out of the sending unit. Just a continuous 5 volts. I did notice though that only the RECEIVE LED lit on the SENDING unit as I pressed the send key. It was not the receiving board that lit. I may have got that screwed up when I noted it earlier. Now I'm not so sure of what I saw previously. Just now, I replaced the sketch with BLINK. The pins 4&5 are then 0 volts. Lastly I just took one of the nano's I was using for this experiment and put a DHT sensor on it, then loaded a DHT sketch. It works fine and everything prints out in the serial monitor. Must be something in my code? One more thing.....I have tried many sketches from different folks using the HC-12 in various capacities. So far, I haven't got any of them to work, not even the simple ones.

Mitch

If you get a chance, maybe upload a picture showing your wiring, just on the off chance there's pin transposition happening.

Arduinos have many layers of pin numbering going on.

 

Everyone,
I sometimes get so involved with what I am doing that I believe I send the right info but I really don't. I was trying to say that yesterday, I had two nano's connected via USB to a laptop, two instances of IDE running at once, and no HC-12's connected. I connected pins 4 & 5 of each micro as transmit and receive per the sketch I was using at the time. I then opened two IDE windows and sent commands using the command line in serial monitor. I was looking for something to go out one USB cable, be transferred from one micro to the other and then come back to the laptop on the other USB cable. That did not happen. I had previously tried to access the HC12's using USB connection running the IDE. I could not get a reply back when I sent the AT command. At the recommendation of Mark Hughes, I removed the HC12's and connected the pins so as to verify that signals were in fact being sent from the micro's. What confuses me now is that with the sketch installed on a micro, the pins both send and receive go high(5V) and stay high as soon as the sketch is loaded. I verified this with an o'scope yesterday.
I currently have a DHT on the micro to verify it is operational and it is working fine. I have also yesterday late and this morning had trouble with my IDE. I deleted and reinstalled a few times before I got it working correctly as best as I can tell. Not sure if that had anything to do with it. I am using 1.8.5, the most current version. I like it because I can poll the micro right from the menu. I am concerned if an older version may be more stable though.
I am going to try the sketch be80be suggested and see what happens. By the way, the sketch Mark wrote is one of many I have tried before coming to the forum for help. It is also one of the nicest and easiest to read I have come across.

 

I had a simple request that you make your post brief and to the point but you can't comply. I am done here.

 

You do Know that you hook RX of uno A to TX of uno B and the TX of uno A to RX of uno B
Same goes for the HC12 hook RX of HC12 to TX of uno and the TX of HC12 to RX of uno

 

If you've tried countless sketches and eliminated all extraneous parts, there's not much left beyond wiring and pin assignments.

Can you share a clear picture of your wiring connections, particularly where the wires go to/from each nano's pins 4 & 5?

 

You do Know that you hook RX of uno A to TX of uno B and the TX of uno A to RX of uno B
Same goes for the HC12 hook RX of HC12 to TX of uno and the TX of HC12 to RX of uno

Yes. I do know that. I have them connected that way. Thanks.

 

If you've tried countless sketches and eliminated all extraneous parts, there's not much left beyond wiring and pin assignments.

Can you share a clear picture of your wiring connections, particularly where the wires go to/from each nano's pins 4 & 5?

I am putting it all back together and I'll send a photo as soon as I am done. Problem is I don't see where to upload a photo on this forum. I would have done that yesterday had I been able to.