RE: How to use the ring buffer library?

Marius — Wed, 14 Aug 2019 08:38:20 GMT

Thank you for this answer. It solved my problem.

RE: How to use the ring buffer library?

Heidi — Tue, 13 Aug 2019 08:38:21 GMT

Hi Marius!

The ring buffer implementation in the SDK does not overwrite old data unless the buffer has been read, so for example

ret_code_t err_code;                                                
uint8_t data1_in[] = {1,2,3,4};                                     
uint8_t data2_in[] = {5,6,7,8};                                     
uint8_t data3_in[] = {9,10,11,12};                                  
uint8_t data1_out[4]; 
uint8_t data2_out[8]; 

size_t  len_in   = sizeof(data1_in);                                 
size_t  len1_out = sizeof(data1_out);                                
size_t  len2_out = sizeof(data2_out);                                

err_code = nrf_ringbuf_cpy_put(&m_ringbuf, data1_in, &len_in);       
err_code = nrf_ringbuf_cpy_put(&m_ringbuf, data2_in, &len_in);       
err_code = nrf_ringbuf_cpy_get(&m_ringbuf, data1_out, &len1_out);    
	
err_code = nrf_ringbuf_cpy_put(&m_ringbuf, data3_in, &len_in);       
err_code = nrf_ringbuf_cpy_get(&m_ringbuf, data2_out, &len2_out);

will give you the output

This can be further confirmed bu examining the implementation of the nrf_ringbuf_cpy_put function in the /components/libraries/nrf_ringbuf.c file. Here, the function calculates available space based in the stored read and write index (rd_idx, wr_idx).

I would suggest using the queue library instead. If you enable NRF_QUEUE_MODE_OVERFLOW, the queue, if full, will overwrite the oldest element.

Best regards,

Heidi