| CMSIS-RTOS Version 1.00 CMSIS-RTOS API: Generic RTOS interface for Cortex-M processor-based devices.

- CMSIS
- CORE
- DSP
- RTOS API
- SVD

- Main Page
- Usage and Description
- Reference

Defines | Functions
Message Queue Management
CMSIS-RTOS API

Control, send, receive, or wait for messages. More...

## Defines

#define | osFeature_MessageQ 1
| Message Queues: 1=available, 0=not available.
#define | osMessageQDef(name, queue_sz, type)
| Create a Message Queue Definition.
#define | osMessageQ(name) &os_messageQ_def_##name
| Access a Message Queue Definition.

## Functions

osMessageQId | osMessageCreate (osMessageQDef_t *queue_def, osThreadId thread_id)
| Create and Initialize a Message Queue.
osStatus | osMessagePut (osMessageQId queue_id, uint32_t info, uint32_t millisec)
| Put a Message to a Queue.
osEvent | osMessageGet (osMessageQId queue_id, uint32_t millisec)
| Get a Message or Wait for a Message from a Queue.

## Description

Message Queue Management functions allow to control, send, receive, or wait for messages. A message can be an integer or pointer value that is send to a thread or interrupt service routine.

CMSIS-RTOS Message Queue

## Define Documentation

#define osFeature_MessageQ 1

A CMSIS-RTOS implementation may support message queues. When the value osFeature_MailQ is 1 message queues are supported. When the value osFeature_MailQ is 0 no message queues are supported.

#define osMessageQ | ( |  | name | ) | &os_messageQ_def_##name

Access to the message queue definition for the function osMessageCreate.

Parameters:

  name | name of the queue

Note:
  CAN BE CHANGED: The parameter to osMessageQ shall be consistent but the macro body is implementation specific in every CMSIS-RTOS.

#define osMessageQDef | ( |  | name,
|  |  | queue_sz,
|  |  | type
| ) |  |

Define the attributes of a message queue created by the function osMessageCreate using osMessageQ.

Parameters:

  name | name of the queue.
  queue_sz | maximum number of messages in the queue.
  type | data type of a single message element (for debugger).

Note:
  CAN BE CHANGED: The parameter to osMessageQDef shall be consistent but the macro body is implementation specific in every CMSIS-RTOS.

## Function Documentation

osMessageQId osMessageCreate | ( | osMessageQDef_t * | queue_def,
|  | osThreadId | thread_id
| ) |  |

Parameters:

  [in] | queue_def | queue definition referenced with osMessageQ.
  [in] | thread_id | thread ID (obtained by osThreadCreate or osThreadGetId) or NULL.

Returns:
  message queue ID for reference by other functions or NULL in case of error.

Note:
  MUST REMAIN UNCHANGED: osMessageCreate shall be consistent in every CMSIS-RTOS.

Create and initialize a message queue.

osEvent osMessageGet | ( | osMessageQId | queue_id,
|  | uint32_t | millisec
| ) |  |

Parameters:

  [in] | queue_id | message queue ID obtained with osMessageCreate.
  [in] | millisec | timeout value or 0 in case of no time-out.

Returns:
  event information that includes status code.

Note:
  MUST REMAIN UNCHANGED: osMessageGet shall be consistent in every CMSIS-RTOS.

Suspend the execution of the current RUNNING thread until a message arrives. When a message is already in the queue, the function returns instantly with the message information. When millisec is 0, the function returns instantly with status osOK. Otherwise the thread is put into the state WAITING. When millisec is set to osWaitForever the function will wait for an infinite time until a message arrives.

Note:
  The parameter millisec must be 0 for using this function in an ISR.

Status and Error Codes

- osOK: no message is available in the queue and no timeout was specified.
- osEventTimeout: no message has arrived during the given timeout period.
- osEventMessage: message received, value.p contains the pointer to message.
- osErrorParameter: a parameter is invalid or outside of a permitted range.

osStatus osMessagePut | ( | osMessageQId | queue_id,
|  | uint32_t | info,
|  | uint32_t | millisec
| ) |  |

Parameters:

  [in] | queue_id | message queue ID obtained with osMessageCreate.
  [in] | info | message information.
  [in] | millisec | timeout value or 0 in case of no time-out.

Returns:
  status code that indicates the execution status of the function.

Note:
  MUST REMAIN UNCHANGED: osMessagePut shall be consistent in every CMSIS-RTOS.

Put the message info in a message queue specified by queue_id. When the message queue is full, the system retry for a specified time with millisec. In this case, the tread is put into the state WAITING. When millisec is set to osWaitForever, the function will wait for an infinite time until a message queue slot becomes available.

Note:
  The parameter millisec must be 0 for using this function in an ISR.

Status and Error Codes

- osOK: the message is put into the queue.
- osErrorResource: no memory in the queue was available.
- osErrorTimeoutResource: no memory in the queue was available during the given time limit.
- osErrorParameter: a parameter is invalid or outside of a permitted range.