Chapter 2. API Reference
Note: Each item stored in No-Split or Allow-Split buffers will require an additional 8 bytes for a header. Item
sizes will also be rounded up to a 32-bit aligned size (multiple of 4 bytes), however the true item size is recorded
within the header. The sizes of No-Split and Allow-Split buffers will also be rounded up when created.
Usage The following example demonstrates the usage of xRingbufferCreate() and xRing-
bufferSend() to create a ring buffer and then send an item to it.
#include "freertos/ringbuf.h"
static char tx_item[] = "test_item";
...
//Create ring buffer
RingbufHandle_t buf_handle;
buf_handle = xRingbufferCreate(1028, RINGBUF_TYPE_NOSPLIT);
if (buf_handle == NULL) {
printf("Failed to create ring buffer\n");
}
//Send an item
UBaseType_t res = xRingbufferSend(buf_handle, tx_item, sizeof(tx_item), pdMS_
,→TO_TICKS(1000));
if (res != pdTRUE) {
printf("Failed to send item\n");
}
The following example demonstrates the usage of xRingbufferSendAcquire() and xRingbufferSend-
Complete() instead of xRingbufferSend() to acquire memory on the ring buffer (of type RING-
BUF_TYPE_NOSPLIT) and then send an item to it. This adds one more step, but allows getting the address of
the memory to write to, and writing to the memory yourself.
#include "freertos/ringbuf.h"
#include "soc/lldesc.h"
typedef struct {
lldesc_t dma_desc;
uint8_t buf[1];
} dma_item_t;
#define DMA_ITEM_SIZE(N) (sizeof(lldesc_t)+(((N)+3)&(~3)))
...
//Retrieve space for DMA descriptor and corresponding data buffer
//This has to be done with SendAcquire, or the address may be different when␣
,→we copy
dma_item_t item;
UBaseType_t res = xRingbufferSendAcquire(buf_handle,
&item, DMA_ITEM_SIZE(buffer_size), pdMS_TO_TICKS(1000));
if (res != pdTRUE) {
printf("Failed to acquire memory for item\n");
}
item->dma_desc = (lldesc_t) {
.size = buffer_size,
.length = buffer_size,
.eof = 0,
.owner = 1,
.buf = &item->buf,
};
(continues on next page)
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