C/C++ - RS232 Bricklet

This is the description of the C/C++ API bindings for the RS232 Bricklet. General information and technical specifications for the RS232 Bricklet are summarized in its hardware description.

An installation guide for the C/C++ API bindings is part of their general description.

Examples

The example code below is Public Domain (CC0 1.0).

Loopback

Download (example_loopback.c)

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#include <stdio.h>

// For this example connect the RX1 and TX pin to receive the send message

#include "ip_connection.h"
#include "bricklet_rs232.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change XYZ to the UID of your RS232 Bricklet

// Callback function for read callback
void cb_read(char message[60], uint8_t length, void *user_data) {
    (void)user_data; // avoid unused parameter warning

    // Assume that the message consists of ASCII characters and
    // convert it from an array of chars to a NUL-terminated string
    char buffer[61]; // +1 for the NUL-terminator
    memcpy(buffer, message, length);
    buffer[length] = '\0';

    printf("Message (Length: %d): \"%s\"\n", length, buffer);
}

int main(void) {
    // Create IP connection
    IPConnection ipcon;
    ipcon_create(&ipcon);

    // Create device object
    RS232 rs232;
    rs232_create(&rs232, UID, &ipcon);

    // Connect to brickd
    if(ipcon_connect(&ipcon, HOST, PORT) < 0) {
        fprintf(stderr, "Could not connect\n");
        return 1;
    }
    // Don't use device before ipcon is connected

    // Register read callback to function cb_read
    rs232_register_callback(&rs232,
                            RS232_CALLBACK_READ,
                            (void (*)(void))cb_read,
                            NULL);

    // Enable read callback
    rs232_enable_read_callback(&rs232);

    // Write "test" string
    char buffer[60] = "test";
    uint8_t written;
    rs232_write(&rs232, buffer, 4, &written);

    printf("Press key to exit\n");
    getchar();
    rs232_destroy(&rs232);
    ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
    return 0;
}

API

Every function of the C/C++ bindings returns an integer which describes an error code. Data returned from the device, when a getter is called, is handled via output parameters. These parameters are labeled with the ret_ prefix.

Possible error codes are:

  • E_OK = 0
  • E_TIMEOUT = -1
  • E_NO_STREAM_SOCKET = -2
  • E_HOSTNAME_INVALID = -3
  • E_NO_CONNECT = -4
  • E_NO_THREAD = -5
  • E_NOT_ADDED = -6 (unused since C/C++ bindings version 2.0.0)
  • E_ALREADY_CONNECTED = -7
  • E_NOT_CONNECTED = -8
  • E_INVALID_PARAMETER = -9
  • E_NOT_SUPPORTED = -10
  • E_UNKNOWN_ERROR_CODE = -11
  • E_STREAM_OUT_OF_SYNC = -12
  • E_INVALID_UID = -13
  • E_NON_ASCII_CHAR_IN_SECRET = -14

as defined in ip_connection.h.

All functions listed below are thread-safe.

Basic Functions

void rs232_create(RS232 *rs232, const char *uid, IPConnection *ipcon)
Parameters:
  • rs232 – Type: RS232 *
  • uid – Type: const char *
  • ipcon – Type: IPConnection *

Creates the device object rs232 with the unique device ID uid and adds it to the IPConnection ipcon:

RS232 rs232;
rs232_create(&rs232, "YOUR_DEVICE_UID", &ipcon);

This device object can be used after the IP connection has been connected (see examples above).

void rs232_destroy(RS232 *rs232)
Parameters:
  • rs232 – Type: RS232 *

Removes the device object rs232 from its IPConnection and destroys it. The device object cannot be used anymore afterwards.

int rs232_write(RS232 *rs232, char message[60], uint8_t length, uint8_t *ret_written)
Parameters:
  • rs232 – Type: RS232 *
  • message – Type: char[60]
  • length – Type: uint8_t, Range: [0 to 60]
Output Parameters:
  • ret_written – Type: uint8_t, Range: [0 to 60]
Returns:
  • error_code – Type: int

Writes a string of up to 60 characters to the RS232 interface. The string can be binary data, ASCII or similar is not necessary.

The length of the string has to be given as an additional parameter.

The return value is the number of bytes that could be written.

See rs232_set_configuration() for configuration possibilities regarding baudrate, parity and so on.

int rs232_read(RS232 *rs232, char ret_message[60], uint8_t *ret_length)
Parameters:
  • rs232 – Type: RS232 *
Output Parameters:
  • ret_message – Type: char[60]
  • ret_length – Type: uint8_t, Range: [0 to 60]
Returns:
  • error_code – Type: int

Returns the currently buffered message. The maximum length of message is 60. If the length is given as 0, there was no new data available.

Instead of polling with this function, you can also use callbacks. See rs232_enable_read_callback() and RS232_CALLBACK_READ callback.

int rs232_set_configuration(RS232 *rs232, uint8_t baudrate, uint8_t parity, uint8_t stopbits, uint8_t wordlength, uint8_t hardware_flowcontrol, uint8_t software_flowcontrol)
Parameters:
  • rs232 – Type: RS232 *
  • baudrate – Type: uint8_t, Range: See constants, Default: 11
  • parity – Type: uint8_t, Range: See constants, Default: 0
  • stopbits – Type: uint8_t, Range: See constants, Default: 1
  • wordlength – Type: uint8_t, Range: See constants, Default: 8
  • hardware_flowcontrol – Type: uint8_t, Range: See constants, Default: 0
  • software_flowcontrol – Type: uint8_t, Range: See constants, Default: 0
Returns:
  • error_code – Type: int

Sets the configuration for the RS232 communication.

Hard-/Software flow control can either be on or off but not both simultaneously on.

The following constants are available for this function:

For baudrate:

  • RS232_BAUDRATE_300 = 0
  • RS232_BAUDRATE_600 = 1
  • RS232_BAUDRATE_1200 = 2
  • RS232_BAUDRATE_2400 = 3
  • RS232_BAUDRATE_4800 = 4
  • RS232_BAUDRATE_9600 = 5
  • RS232_BAUDRATE_14400 = 6
  • RS232_BAUDRATE_19200 = 7
  • RS232_BAUDRATE_28800 = 8
  • RS232_BAUDRATE_38400 = 9
  • RS232_BAUDRATE_57600 = 10
  • RS232_BAUDRATE_115200 = 11
  • RS232_BAUDRATE_230400 = 12

For parity:

  • RS232_PARITY_NONE = 0
  • RS232_PARITY_ODD = 1
  • RS232_PARITY_EVEN = 2
  • RS232_PARITY_FORCED_PARITY_1 = 3
  • RS232_PARITY_FORCED_PARITY_0 = 4

For stopbits:

  • RS232_STOPBITS_1 = 1
  • RS232_STOPBITS_2 = 2

For wordlength:

  • RS232_WORDLENGTH_5 = 5
  • RS232_WORDLENGTH_6 = 6
  • RS232_WORDLENGTH_7 = 7
  • RS232_WORDLENGTH_8 = 8

For hardware_flowcontrol:

  • RS232_HARDWARE_FLOWCONTROL_OFF = 0
  • RS232_HARDWARE_FLOWCONTROL_ON = 1

For software_flowcontrol:

  • RS232_SOFTWARE_FLOWCONTROL_OFF = 0
  • RS232_SOFTWARE_FLOWCONTROL_ON = 1
int rs232_get_configuration(RS232 *rs232, uint8_t *ret_baudrate, uint8_t *ret_parity, uint8_t *ret_stopbits, uint8_t *ret_wordlength, uint8_t *ret_hardware_flowcontrol, uint8_t *ret_software_flowcontrol)
Parameters:
  • rs232 – Type: RS232 *
Output Parameters:
  • ret_baudrate – Type: uint8_t, Range: See constants, Default: 11
  • ret_parity – Type: uint8_t, Range: See constants, Default: 0
  • ret_stopbits – Type: uint8_t, Range: See constants, Default: 1
  • ret_wordlength – Type: uint8_t, Range: See constants, Default: 8
  • ret_hardware_flowcontrol – Type: uint8_t, Range: See constants, Default: 0
  • ret_software_flowcontrol – Type: uint8_t, Range: See constants, Default: 0
Returns:
  • error_code – Type: int

Returns the configuration as set by rs232_set_configuration().

The following constants are available for this function:

For ret_baudrate:

  • RS232_BAUDRATE_300 = 0
  • RS232_BAUDRATE_600 = 1
  • RS232_BAUDRATE_1200 = 2
  • RS232_BAUDRATE_2400 = 3
  • RS232_BAUDRATE_4800 = 4
  • RS232_BAUDRATE_9600 = 5
  • RS232_BAUDRATE_14400 = 6
  • RS232_BAUDRATE_19200 = 7
  • RS232_BAUDRATE_28800 = 8
  • RS232_BAUDRATE_38400 = 9
  • RS232_BAUDRATE_57600 = 10
  • RS232_BAUDRATE_115200 = 11
  • RS232_BAUDRATE_230400 = 12

For ret_parity:

  • RS232_PARITY_NONE = 0
  • RS232_PARITY_ODD = 1
  • RS232_PARITY_EVEN = 2
  • RS232_PARITY_FORCED_PARITY_1 = 3
  • RS232_PARITY_FORCED_PARITY_0 = 4

For ret_stopbits:

  • RS232_STOPBITS_1 = 1
  • RS232_STOPBITS_2 = 2

For ret_wordlength:

  • RS232_WORDLENGTH_5 = 5
  • RS232_WORDLENGTH_6 = 6
  • RS232_WORDLENGTH_7 = 7
  • RS232_WORDLENGTH_8 = 8

For ret_hardware_flowcontrol:

  • RS232_HARDWARE_FLOWCONTROL_OFF = 0
  • RS232_HARDWARE_FLOWCONTROL_ON = 1

For ret_software_flowcontrol:

  • RS232_SOFTWARE_FLOWCONTROL_OFF = 0
  • RS232_SOFTWARE_FLOWCONTROL_ON = 1
int rs232_set_break_condition(RS232 *rs232, uint16_t break_time)
Parameters:
  • rs232 – Type: RS232 *
  • break_time – Type: uint16_t, Unit: 1 ms, Range: [0 to 216 - 1]
Returns:
  • error_code – Type: int

Sets a break condition (the TX output is forced to a logic 0 state). The parameter sets the hold-time of the break condition.

New in version 2.0.2 (Plugin).

Advanced Functions

int rs232_get_identity(RS232 *rs232, char ret_uid[8], char ret_connected_uid[8], char *ret_position, uint8_t ret_hardware_version[3], uint8_t ret_firmware_version[3], uint16_t *ret_device_identifier)
Parameters:
  • rs232 – Type: RS232 *
Output Parameters:
  • ret_uid – Type: char[8]
  • ret_connected_uid – Type: char[8]
  • ret_position – Type: char, Range: ['a' to 'h', 'i', 'z']
  • ret_hardware_version – Type: uint8_t[3]
    • 0: major – Type: uint8_t, Range: [0 to 255]
    • 1: minor – Type: uint8_t, Range: [0 to 255]
    • 2: revision – Type: uint8_t, Range: [0 to 255]
  • ret_firmware_version – Type: uint8_t[3]
    • 0: major – Type: uint8_t, Range: [0 to 255]
    • 1: minor – Type: uint8_t, Range: [0 to 255]
    • 2: revision – Type: uint8_t, Range: [0 to 255]
  • ret_device_identifier – Type: uint16_t, Range: [0 to 216 - 1]
Returns:
  • error_code – Type: int

Returns the UID, the UID where the Bricklet is connected to, the position, the hardware and firmware version as well as the device identifier.

The position can be 'a', 'b', 'c', 'd', 'e', 'f', 'g' or 'h' (Bricklet Port). The Raspberry Pi HAT (Zero) Brick is always at position 'i' and the Bricklet connected to an Isolator Bricklet is always as position 'z'.

The device identifier numbers can be found here. There is also a constant for the device identifier of this Bricklet.

Callback Configuration Functions

void rs232_register_callback(RS232 *rs232, int16_t callback_id, void (*function)(void), void *user_data)
Parameters:
  • rs232 – Type: RS232 *
  • callback_id – Type: int16_t
  • function – Type: void (*)(void)
  • user_data – Type: void *

Registers the given function with the given callback_id. The user_data will be passed as the last parameter to the function.

The available callback IDs with corresponding function signatures are listed below.

int rs232_enable_read_callback(RS232 *rs232)
Parameters:
  • rs232 – Type: RS232 *
Returns:
  • error_code – Type: int

Enables the RS232_CALLBACK_READ callback.

By default the callback is disabled.

int rs232_disable_read_callback(RS232 *rs232)
Parameters:
  • rs232 – Type: RS232 *
Returns:
  • error_code – Type: int

Disables the RS232_CALLBACK_READ callback.

By default the callback is disabled.

int rs232_is_read_callback_enabled(RS232 *rs232, bool *ret_enabled)
Parameters:
  • rs232 – Type: RS232 *
Output Parameters:
  • ret_enabled – Type: bool, Default: false
Returns:
  • error_code – Type: int

Returns true if the RS232_CALLBACK_READ callback is enabled, false otherwise.

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the rs232_register_callback() function:

void my_callback(int value, void *user_data) {
    printf("Value: %d\n", value);
}

rs232_register_callback(&rs232,
                        RS232_CALLBACK_EXAMPLE,
                        (void (*)(void))my_callback,
                        NULL);

The available constants with corresponding function signatures are described below.

Note

Using callbacks for recurring events is always preferred compared to using getters. It will use less USB bandwidth and the latency will be a lot better, since there is no round trip time.

RS232_CALLBACK_READ
void callback(char message[60], uint8_t length, void *user_data)
Callback Parameters:
  • message – Type: char[60]
  • length – Type: uint8_t, Range: [1 to 60]
  • user_data – Type: void *

This callback is called if new data is available. The message has a maximum size of 60 characters. The actual length of the message is given in addition.

To enable this callback, use rs232_enable_read_callback().

RS232_CALLBACK_ERROR
void callback(uint8_t error, void *user_data)
Callback Parameters:
  • error – Type: uint8_t, Range: See constants
  • user_data – Type: void *

This callback is called if an error occurs. Possible errors are overrun, parity or framing error.

The following constants are available for this function:

For error:

  • RS232_ERROR_OVERRUN = 1
  • RS232_ERROR_PARITY = 2
  • RS232_ERROR_FRAMING = 4

New in version 2.0.1 (Plugin).

Virtual Functions

Virtual functions don't communicate with the device itself, but operate only on the API bindings device object. They can be called without the corresponding IP Connection object being connected.

int rs232_get_api_version(RS232 *rs232, uint8_t ret_api_version[3])
Parameters:
  • rs232 – Type: RS232 *
Output Parameters:
  • ret_api_version – Type: uint8_t[3]
    • 0: major – Type: uint8_t, Range: [0 to 255]
    • 1: minor – Type: uint8_t, Range: [0 to 255]
    • 2: revision – Type: uint8_t, Range: [0 to 255]
Returns:
  • error_code – Type: int

Returns the version of the API definition implemented by this API bindings. This is neither the release version of this API bindings nor does it tell you anything about the represented Brick or Bricklet.

int rs232_get_response_expected(RS232 *rs232, uint8_t function_id, bool *ret_response_expected)
Parameters:
  • rs232 – Type: RS232 *
  • function_id – Type: uint8_t, Range: See constants
Output Parameters:
  • ret_response_expected – Type: bool
Returns:
  • error_code – Type: int

Returns the response expected flag for the function specified by the function ID parameter. It is true if the function is expected to send a response, false otherwise.

For getter functions this is enabled by default and cannot be disabled, because those functions will always send a response. For callback configuration functions it is enabled by default too, but can be disabled by rs232_set_response_expected(). For setter functions it is disabled by default and can be enabled.

Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For function_id:

  • RS232_FUNCTION_ENABLE_READ_CALLBACK = 3
  • RS232_FUNCTION_DISABLE_READ_CALLBACK = 4
  • RS232_FUNCTION_SET_CONFIGURATION = 6
  • RS232_FUNCTION_SET_BREAK_CONDITION = 10
int rs232_set_response_expected(RS232 *rs232, uint8_t function_id, bool response_expected)
Parameters:
  • rs232 – Type: RS232 *
  • function_id – Type: uint8_t, Range: See constants
  • response_expected – Type: bool
Returns:
  • error_code – Type: int

Changes the response expected flag of the function specified by the function ID parameter. This flag can only be changed for setter (default value: false) and callback configuration functions (default value: true). For getter functions it is always enabled.

Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For function_id:

  • RS232_FUNCTION_ENABLE_READ_CALLBACK = 3
  • RS232_FUNCTION_DISABLE_READ_CALLBACK = 4
  • RS232_FUNCTION_SET_CONFIGURATION = 6
  • RS232_FUNCTION_SET_BREAK_CONDITION = 10
int rs232_set_response_expected_all(RS232 *rs232, bool response_expected)
Parameters:
  • rs232 – Type: RS232 *
  • response_expected – Type: bool
Returns:
  • error_code – Type: int

Changes the response expected flag for all setter and callback configuration functions of this device at once.

Constants

RS232_DEVICE_IDENTIFIER

This constant is used to identify a RS232 Bricklet.

The rs232_get_identity() function and the IPCON_CALLBACK_ENUMERATE callback of the IP Connection have a device_identifier parameter to specify the Brick's or Bricklet's type.

RS232_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a RS232 Bricklet.