Thread: Tricky request and response structure.

Hi Friends,

I have to implement a request_response function. This function has two arguments one is request command structure and other is response structure which is filled after getting response. Its 8-bytes i.e.,

Code:

typdef struct{
uint16_t data0;
uint16_t data1;
uint16_t data2;
uint16_t data3;
}data_st;

extern data_st request;
extern data_st response;

request_response(&request, &response);

There are 3-4 set of request and response. Which is sent one by one.
When request0 is sent first response must be discarded as there is 8-bytes(64 bits) gap in response from the other system. When request1 is sent response0 is gotten. Same way request2 is sent response1 is received. Same way request..n ...response..n-1 and request_dummy will be sent in the last to receive response..n.

I have to collect the correct response for a request. Means need to map response0 for request0 , response1 for request1 and response2 for request2 for further processing.

How to manage this? Please help.

Thanks,
david.

request_dummy (say 0x00 ) will be sent in the last to receive response'n'.

Thanks,
david.

You mean something like this?

Code:

type request[5] = { request-1, request-2, request-3, request-4, request-dummy };
type response[5];

for i = 0 -> 4:
    request_response(&request[i], &response[i]);

for i = 0 -> 3:
    request[i] is associated with response[i + 1]

Yes..Correct. One time only one request will be sent and response of the previous request will be received. Then next. Please guide how to achieve this?
Thanks.

Originally Posted by davidmeetsall

Please guide how to achieve this?

Is the pseudocode I posted not adequate for expressing the logic you need? If not, explain how it's lacking. Otherwise, what's stopping you from implementing the code using the pseudocode as reference?

You seem to be suggesting something like this (essentially the same as Matticus suggested).

Code:

request_response(&request0, &response_dummy);
request_response(&request1, &response0);
request_response(&request2, &response1);
request_response(&request3, &response2);
request_response(&request_dummy, &response3);

Instead of defining all the separate request variables, you could load request with the appropriate values before each call. You could use the same response variable, too, if you transfer the valid data somewhere else as appropriate.

Actually, Its a state machine implementation for SPI communication in PIC microcontroller. No for loop is used. One request will be sent at the same time previous response will be received. Then Next request etc.. I am confused as I have to process the responses for the same requests in some cases. I hope this makes clear.

Hi Algorism and matticus,


I am doing the same as you suggested. But the problem is in a switch case I have to process the result.

Code:

case request1:
  send (response1);
case request2:
  send (response2);
case request3:
  send (response3);

How to handle above?


Thanks.

Sorry more appropriately...this has to be done next..

Code:

case request1.data0:
  send (response1.data2);
case request2.data0:
  send (response2.data3);
case request3.data:
  send (response3.data2);

How to handle above?

Do you have to process a response as soon as it's received, or can you gather responses then process them after the "3-4 set of request and response" is complete?

I have to process a response as soon as it's received. Please suggest the best possible way. Thanks.
David.

Hi Algorism,

Thanks a lot. It looks like this will work and its as per my requirement. I will try and let you know if I face any issue. Thanks.

Hi Algorism,

Sorry for informing late. I implemented as per your suggestion making the adjustment in my existing code.
It works to some extent. The problem I am facing is that, REQUEST0, REQUEST1, REQUEST2, REQUEST3 all work as there is always a next command is there. Like, REQUEST1 is next command for REQUEST0, REQUEST2 is next command for REQUEST1 and so on. But issue here is once REQUEST4 is sent I need to keep repeating sending this command for 3 different modes. Once this is done again REQUEST4 is to be sent for 3 different modes and so on. And data processed for all modes must match with the request as said in my earlier posts.

Code:

case REQUEST4:
        request_response(&request[4], &response);
        if (prev_request != REQUEST_NONE)
            handle_prev_response(prev_request, &response);
        prev_request = REQUEST3;
        break;
//...
}



void handle_prev_response(RequestType rt, data_st *response) {
    switch (rt) {
    case REQUEST3:
        // process response for request-3 type
        break;
    case REQUEST4:   ////send same REQUEST4 for 3 different modes and repeat again
        // process response for request-4 type mode1
    break;

    case REQUEST4:
        // process response for request-4 type mode2
    break;
    case REQUEST4:
        // process response for request-4 type mode3


        break;
 case REQUEST4:   ////send same REQUEST4 for 3 different modes and repeat again
        // process response for request-4 type mode1

    // etc.
    }
}

How to achieve this? Please help.

--david.