Simple way of adding data in repeated fields

[sondre....@gmail.com]

Hi guys,

I'm using protobuf/nanoPB to exchange data between a micro controller and a raspberry pi. I'm relatively new to nanoPB and struggle a bit with repeated fields. In the example below I set all the values except for the repeated temperature fields, and it works great.

Proto file:

syntax = "proto2";

message SimpleMessage
{
message TemperatureSensorData
{
optional int32 temperature = 1;
optional int32 errorFlag = 2;
}

message Motor
{
optional int32 id = 1;
optional int32 voltage = 2;
optional int32 current = 3;
repeated TemperatureSensorData motorTemperature = 4;
}

optional Motor motor = 1;
}

Simple example program to encode and decode:

#include <iostream>
#include <stdlib.h>
#include <pb_encode.h>
#include <pb_decode.h>
#include "SimpleRepeated.pb.h"

int main(int argc, char *argv[])
{
uint8_t buffer[128];
size_t message_length;
bool status;

/* Encode */
{
SimpleMessage message = SimpleMessage_init_zero;

/* Create a stream that will write to our buffer. */
pb_ostream_t stream = pb_ostream_from_buffer(buffer, sizeof(buffer));

// Fill in data
message.has_motor = true;
message.motor.has_id = true;
message.motor.id = 1;
message.motor.has_voltage = true;
message.motor.voltage = 24;
message.motor.has_current = true;
message.motor.current = 3;

/* Now we are ready to encode the message! */
status = pb_encode(&stream, SimpleMessage_fields, &message);
message_length = stream.bytes_written;

/* Then just check for any errors.. */
if (!status)
{
printf("Encoding failed: %s\n", PB_GET_ERROR(&stream));
return 1;
}
}

/* Decode */
{
/* Allocate space for the decoded message. */
SimpleMessage message = SimpleMessage_init_zero;

/* Create a stream that reads from the buffer. */
pb_istream_t stream = pb_istream_from_buffer(buffer, message_length);

/* Now we are ready to decode the message. */
status = pb_decode(&stream, SimpleMessage_fields, &message);

/* Check for errors... */
if (!status)
{
printf("Decoding failed: %s\n", PB_GET_ERROR(&stream));
return 1;
}

/* Print the data contained in the message. */
std::cout << "ID= " << message.motor.id << std::endl;
std::cout << "Voltage= " << message.motor.voltage << std::endl;
std::cout << "Current= " << message.motor.current << std::endl;
}

return 0;
}

What is the easiest way of adding temperature values? I tried something like this:

for(uint8_t i=0; i<5; i++)
{
message.motor.motorTemperature[i].temperature = i;
message.motor.motorTemperature[i].errorFlag = i*i;
}

but it won't compile. The l

Best regards,
Sondre

[Petteri Aimonen]

Hi,

> What is the easiest way of adding temperature values? I tried something like this:
>
> for(uint8_t i=0; i<5; i++)
> {
> message.motor.motorTemperature[i].temperature = i;
> message.motor.motorTemperature[i].errorFlag = i*i;
> }
>
> but it won't compile.

You'll need to add a maximum count option to the repeated field. For
example, create a SimpleRepeated.options file with the following
content:

SimpleMessage.Motor.motorTemperature max_count:5

After that in the generated .pb.h you should see a simple array you can
access like you expected, and a _count field that you should set to the
number of entries in the array.

--
Petteri

[sondre....@gmail.com]

Thank you, Petteri!

It worked perfectly :)

Best regards
Sondre

[Divith sid H]

Can you share full code.. i'm stuck at adding multiple values under repeated field