hsersend and hserreceive with one microcontroller

[JANIS]

hello! I want to establish data exchange between two microcontrollers, transmit data to one side (one microcontroller transmits, the other microcontroller acts as a receiver) is not a problem, but the data exchange simultaneously (each microcontroller acts as both a transmitter and as a receiver) between microcontrollers I can not made.

Just RECEIVE and just RECEIVE - no problem,
16f628a as receiver:

    #chip 16f628a, 4
    #config osc=int
    #define USART_BAUD_RATE 9600
    #define USART_BLOCKING

    Dir PORTb.2 in 'Rx   hserreceive
    dir portb.3 out                              'PWM
    #define PWM_OUT1 PORTa.1
    dir PWM_OUT1 out
    cycle:
     'SerReceive 1, portanew
    portanew = hSerReceive
    pwmout 1, portanew,  1
    wait 5 ms
    goto cycle

16f88 as transmitter:

    #chip 16f88, 4
    #config osc=int
    #define USART_BAUD_RATE 9600
    #define USART_BLOCKING
        Dir PORTb.5 out   ' Tx                            
    dir an1 in  'porta.1
    cycle:

    hsersend readad(an1)

    wait 5 ms
    goto cycle

with one microcontroller-both transmit and receive - not working:

    16f628a as transmitter&receiver:
    #chip 16f628a, 4
    #config osc=int
    #define USART_BAUD_RATE 9600
    #define USART_BLOCKING

    Dir PORTb.1 out  ' Tx hsersend
    dir porta.0 in
    Dir PORTb.2 in 'Rx   hserreceive

    #define PWM_OUT1 PORTa.1 'PWM
    dir PWM_OUT1 out

    cycle:

    hsersend porta.0 ' switch - as bit

    portanew = hSerReceive
    pwmout 1, portanew,  1
    wait 5 ms
    goto cycle

16f88 as transmitter&receiver:

    #chip 16f88, 4
    #config osc=int
    #define USART_BAUD_RATE 9600
    #define USART_BLOCKING

    Dir PORTb.5 out   ' Tx                           
    dir an1 in  'porta.1
    dir portb.3 out  'led

    dir portb.2 in  'Rx

    cycle:

    hsersend readad(an1) ' byte
    porta.1 = hSerReceive
    if  porta.1=1 then         
    portb.3=on
    else
    portb.3=off
    end if

    wait 5 ms
    goto cycle

how to realize data exchange between the microcontrollers on both sides simultaneously or it is impossible?? I hope to any help!

Edited to make this readable... please use four tilders to at top and bottom of code.

[Anobium]

My thoughts. Is this a sync issue. What do I mean? You have two processors one talking and one listening and they are out of sync.

Add a connection on a spare port, pull to high with a 4.7k. Then, prior to sending from one device check the port is high (so the port is at this stage an input), if high then pull the port low (so change port to output, then set low), then send the data, then set port to input. Do this for both devices. It will ensure you only send when the other device is in a position to 'listen'.

However, I would use I2C for this transmission. It would be easier. :-)

[kent_twt4]

Another idea is having the receiver wait for an ascii command, like EOT (end of transmission), to toggle between receive and transmit. This would require reserving a dec number (like 255) with HSer send/rec: OR, more overhead on both ends to perform bin2ascii, and asciitobin, type operations to differentiate EOT ascii type commands from the dec numbers.

Do Until value = 255
value = HserReceive
....
....
Loop

[JANIS]

Thanks for the reply, Anobium!Let's try to connect the resistors.
My idea is as follows - use 16F88 analog input temperature transfer (byte), but the data it receives for execution configured for output ports(bits). The second micro-controller 16f628 I want to use to indicate temperatures (received data), but the processed information back to the 16F88 output ports.
Distance between microcontrollers will be 50m, so the data transfer thinking of using MAX485, then I2C can not be used ...? But first I want to run usart between both microcontrollers. Perhaps the need to use other microcontrollers? Sorry for my English. My program code example can run?

[Anobium]

@Kent. A great idea. The power of community.

In my projects (in the past...) I used to send a few "U" or 0x55 as the sync code followed the data. The idea of sending 0x55 is that this is transmitted as "0101010102 this would bring the serial circuit into a steady state. Then, as you recommended, wait until your receive the 0x55's then you know you are in sync.

Or, simple use Kent's recommendation. :-)

Thinking about the idea... I could document and put in the help file.

[JANIS]

Thank you, kent_twt4 ! Does your idea will work in my case?

[Anobium]

Both ideas will work. I would go with the Kents idea. Its easier and you do not need to tie up a port.

Post your code if you have any issues.

[JANIS]

I am a beginner in the world of microcontrollers,Anobium and kent_twt4 are professionals maybe you can give some examples of program code for my case?? My idea of ​​the project is clear to you. Thanks!

[kent_twt4]

Use a terminal to act as one of the Pic transceivers. Type in a byte or two with the termination code on the terminal. Have the other Pic echo back what was typed in, or an acknowledgement of some type to confirm.

[JANIS]

I connect resistors as recommended anobium, it did not help :((((

[Anobium]

Let start again. :-)
You have at least three options (I am sure there are more), they are: I2C, three wire serial, two wire serial.
You cannot use I2C as your requirement of 50m will prevent this without adding more complexity.
You could you use three wire serial. This uses the pull up resistor as I described.
Finally, you have two wire serial. This is the method Kent recommended and I think will work for you. You do not need pull resistors for this method.

So, remove the resistors and read on. :-)

This is not tested code but this is the approach for same chips.

~~~~~
'Chip Settings
#chip 16F1823,8

;Variables
Dim buffer As string * 1
Dim syncbyte as Byte
Dim loopcount as word

sync = 0x55 ' you can use 255 - your choice

Do
' Send info
Repeat 3
HSerSend syncbyte
end Repeat
HSerSend readad(0)

    ' get info
    loopcount = 0
    Do Until value = syncbyte
      receivedvalue = HserReceive
      loopcount++
      ' intended to stop endless loop... should work
      if loopcount  > 65000 then exit Do
    Loop

Loop

~~~~

[JANIS]

Thank anobium! I will report for results!

[Anobium]

Sorry, I did think about this again.

Here is some code for an RS232 Ring Buffer. This does work. If you send three sync codes the next piece of data is treated as the data to be read. So, in this example you can send thee U's and then the next piece of data is shown on the terminal. I do not have two devices handy to test.

Key parts, the interrupt, the sub and the functions and few constants.

But, essentially the buffer is stored in a buffer and you read via the function 'bget'. If the buffer is empty then 'bkbhit' is not true.

Try in integrate this code.

Good luck.

~~~~~
;Chip Settings

chip 16F1937,32

config LVP=OFF, BODEN=OFF, WDT=OFF, OSC=XT

     #include <outputserial.h>

    ' [todo] This is the config for a serial terminal
    ' turn on the RS232 and terminal port.
    ' Define the USART port
    #define USART_BAUD_RATE 9600
    #define USART_BLOCKING true
    ' [todo] Ensure these port addresses are correct
    #define SerInPort PORTc.7
    #define SerOutPort PORTc.6
    'Set pin directions
    Dir SerOutPort Out
    Dir SerInPort In


    ' [todo] This assumes you are using an ANSI compatible terminal.  Use PUTTY.EXE it is very easy.

    wait 1 s
    ANSIERASECREEN
    ANSI ( 0, 2)
    HSerPrint "Started: Serial between two devices"
    ANSI ( 0, 6)
    crlf(2)

    DIR PORTA.0 IN

;Interrupt Handlers
On Interrupt UsartRX1Ready Call readUSART

' all important!
#define bkbhit (next_in <> next_out)
#define BUFFER_SIZE 8
;Variables
Dim buffer(BUFFER_SIZE)
Dim next_in as byte: next_in = 1
Dim next_out as byte: next_out = 1
Dim syncbyte as Byte

syncbyte = 0x55 ' you can use 255 - your choice

Do
' Send info
' Repeat 3
' HSerSend syncbyte
' end Repeat
' HSerprint readad(an0)

      do while bkbhit

' HSerPrint chr(bgetc)

         if bgetc = syncbyte and bgetc = syncbyte and bgetc = syncbyte then
            HSerPrint "sync'ed '"
            HSerPrint chr(bgetc):CRLF
         end if
      Loop

LOOP

Sub readUSART

    buffer(next_in) = HSerReceive
    temppnt = next_in
    next_in = ( next_in + 1 ) % BUFFER_SIZE
    if ( next_in = next_out ) then  ' buffer is full!!
       next_in = temppnt
    end if

End Sub

function bgetc
   wait while !(bkbhit)
   bgetc = buffer(next_out)
   next_out=(next_out+1) % BUFFER_SIZE
end Function

[JANIS]

Thank Anobium! It is likely that your version works, but it is difficult. For me. Maybe it is probably easier - in one period of time first microcontroller transmit data, but the other to receive, for example - 100ms one microcontroller transmits , other receive data, then 100ms second microcontroller transmits and receives the first ...?

For example:
If time <100 then Hsersend ......
If time> 100 then Hserreceive .....

If time = 200 time = 0 then
.....
.....

[Anobium]

Another go.

This time I have changed the sync tests. To sync to pics is not easy. To read a pic from a pc... is a lot easier!

I have documented a little better for you. You will find the byte of interest in the middle of the Do-Loop.

This time.... we sample the incoming bytes, check for three and then the next is the byte we are interested in. If we do not get a sync byte then we assume that the pic is out of sync and restart the process.

Over to you for testing. Let us know the results.

Anobium

edited. I have got two pics. See attached.
One is a master and the other a slave. The code is very similar but not same.... the master needs to send the data out (see 16f1937) and the slave need to respond (see 16f1947). It make sense now I have seen it working.

I am sending a AD value from the master, receiving at the slave and returning from the slave the same value + turn on LED if value is greater than 127, then when the master gets the data from the slave turn on an LED if value (from the slave) is greater than 127. Then, the master send the next value.

Blows the mind...

[JANIS]

anobium thank you! I'll try to experiment on the results I will report,

[Anobium]

Any progress? I want to break down the test kit I have here.

I need to do a project. :-)

[Anobium]

Any progress? I want to break down the test kit I have here.

I need to do a project. :-)

[JANIS]

while is not progress: (( I'll try tomorrow's serious. But I have only 2 types of microcontrollers - 16f628a 16F88

[JANIS]

hello, anobium! I can not create the code for my chips .... you yourself tried to run your code using test kit? your written code can not compile....

[Anobium]

You may have to the serial terminal. Search for [todo] This code is specific to a serial terminal.