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libbsmp

Basic Small Messages Protocol Library

The BSMP - Basic Small Messages Protocol - is a stateless, synchronous and lightweight protocol. It was designed to be used in serial communication networks of small embedded devices which contain a device with the role of a master.

This protocol manipulates 4 simple things, which are called Entities:

  1. Variables
  2. Groups
  3. Curves
  4. Functions

Variables can be either writable or read-only and have a value of up to 128 bytes.

A Group contains a bunch of Variables that can be read from or written to with only one command.

A Curve can be seen as a very large Variable, with up to 65536 blocks of 65520 bytes each.

Finally, a Function is a very simple way to perform a Remote Procedure Call (RPC).

Installing

Installing the library is very easy:

make
sudo make install

Examples

A full-featured and commented example is available in the examples/full_example folder.

Order of calls for a server

When building a server, this would be the order of the calls to be made. They are not very detailed. They are documented in the server.h header.

#include <bsmp/server.h>       // Header with all the necessary functions
bsmp_server_t srv;             // Server instance
bsmp_server_init(&srv);        // Initialize the instance

// Create a function to intervene before reads and after writes, if
// necessary
void hook(enum bsmp_operation op, struct bsmp_var **list)
{
    ...
}

bsmp_register_hook(&server,hook);    // Register the hook with the server

struct bsmp_var v = {...};     // Create a variable
bsmp_register_var(&bsmp, &v);  // Register a variable with the server

// Same with bsmp_curve and bsmp_function

// Once everything is registered, just
for(;;)
{
    // Receive a message into a bsmp_raw_packet (recv_pkt here)
    bsmp_process_packet(&srv, &recv_pkt, &send_pkt)
    // Send back the answer in a bsmp_raw_packet (send_pkt in this case)
}

Order of calls for a client

#include <bsmp/client.h>        // Header with all the necessary functions
bsmp_client_t cli;              // Client instance
bsmp_client_init(&cli, send_func, recv_func);    // initialize instance

// Get all entities in the server
struct bsmp_var_info_list *vars;
bsmp_get_vars_list(&cli, &vars);

struct bsmp_group_list *groups;
bsmp_get_groups_list(&cli, &groups);

struct bsmp_curve_info_list *curves;
bsmp_get_curves_list(&cli, &curves);

struct bsmp_func_info_list *funcs;
bsmp_get_funcs_list(&cli, &funcs);

// Manipulate entities

// Read first var
struct bsmp_var_info *first_var = &vars->list[0];
uint8_t first_var_value[first-var->size];
bsmp_read_var(&cli, first_var, first_var_value);

// Write first var
first_var_value[0] = 0x42;
bsmp_write_var(&cli, first_var, first_var_value);

// Consult the header to see how to manipulate other entities (groups, curves,
// and functions.