How to check when the stack is ready to send notification?

RE: How to check when the stack is ready to send notification?

Dmitry Kr — Thu, 22 Oct 2015 08:07:46 GMT

Anders, I changed the MAX_CONN_INTERVAL to 60 ms, but it doesn't helps. Yes, we need slave latency to be able to set different send period and save energy on the peripheral side. For example, period could be set from 100 ms up to 2 sec. How to use slave latency setting?

RE: How to check when the stack is ready to send notification?

Anders Strand — Thu, 22 Oct 2015 07:41:42 GMT

Can you set MAX_CONN_INTERVAL to 60 for the peripheral as well? Slave latency is used for saving power (you sleep through x connection events), do not use this if you need throughput.

RE: How to check when the stack is ready to send notification?

Dmitry Kr — Wed, 21 Oct 2015 09:59:39 GMT

Hi, Andre. Currently slave settings is:

#define MIN_CONN_INTERVAL                   MSEC_TO_UNITS(30, UNIT_1_25_MS)           /**< Minimum acceptable connection interval . */
#define MAX_CONN_INTERVAL                   MSEC_TO_UNITS(1000, UNIT_1_25_MS)          /**< Maximum acceptable connection interval (1 second). */
#define SLAVE_LATENCY                       0                                          /**< Slave latency. */
#define CONN_SUP_TIMEOUT                    MSEC_TO_UNITS(4000, UNIT_10_MS)            /**< Connection supervisory timeout (4 seconds). */

BTW, when I tried to change SLAVE LATENCY, I got the error on sd_ble_gap_ppcp_set() for peripheral and on sd_ble_gap_connect() for central. If it is needed to set connection interval to 30 ms and latency to 33 (at total 1 sec period with 30 ms interval), how it can be made?

RE: How to check when the stack is ready to send notification?

Anders Strand — Wed, 21 Oct 2015 07:22:23 GMT

If you put more packets into the TX_buffer than you send out, it fill naturally fill up. The peripheral is able to send a certain amount of packets each connection interval (6 for S110). With a connection interval of 60ms, it can send (6 * (1/0.060) = 100) packets each second. Even though this is a theoretical maximum, it should be more than enough to send every 100 ms. (See this post for more info on BLE throughput). What is the connection intervals on your peripheral application?

RE: How to check when the stack is ready to send notification?

Dmitry Kr — Tue, 20 Oct 2015 14:24:12 GMT

Andre, thanks a lot. Also, I receive the same error when trying to set faster send period. If I try to send packets frequenly than 100 ms, the same error received. Why this happens if central settings is:

MIN_CONNECTION_INTERVAL          MSEC_TO_UNITS(30, UNIT_1_25_MS)                
MAX_CONNECTION_INTERVAL          MSEC_TO_UNITS(60, UNIT_1_25_MS)                
SLAVE_LATENCY                    0                                              
SUPERVISION_TIMEOUT              MSEC_TO_UNITS(4000, UNIT_10_MS)

RE: How to check when the stack is ready to send notification?

Anders Strand — Tue, 20 Oct 2015 09:38:08 GMT

Since the central is off, the packets are not leaving the TX buffer. Adding more buffers will not help you. In your case, this error can be viewed as a symptom of a disconnect. The disconnect event will not happen before a certain amount of connection intervals have passed (this time is often defined as CONN_SUP_TIMEOUT in our SDK). You can ignore the error if you want, or you can pause the sending of packets until you receive a BLE_EVT_TX_COMPLETE

RE: How to check when the stack is ready to send notification?

Dmitry Kr — Sat, 17 Oct 2015 18:46:42 GMT

Would we made the TX buffer like one in HRS_C example, with re-sending packets got this error?

RE: How to check when the stack is ready to send notification?

Dmitry Kr — Sat, 17 Oct 2015 18:44:49 GMT

Dear Anders, you totally right! Ok, the question is recommendation for program behavior getting this error. Curretnly APP_ERROR_CHECK stops the program or resets CPU depending on debug macro setting. What we should do getting this error code? Could we ignore it?

RE: How to check when the stack is ready to send notification?

Anders Strand — Fri, 16 Oct 2015 09:55:53 GMT

The 0x3004 error is BLE_ERROR_NO_TX_BUFFERS. It is returned when you have no free output buffers to put a packet in. I makes sense that you get this error if you keep trying to send notifications, but the central is off. The packets you put in the buffer after the central is turned off will be stuck there.

RE: How to check when the stack is ready to send notification?

Dmitry Kr — Wed, 14 Oct 2015 15:17:44 GMT

Hi, Anders!

Thank you, it works fine for cccd writes, but there is an error produced on the disconnection, althought BLE_GAP_EVT_DISCONNECTED is monitored. I get the 0x3004 error on the code:

err_code = sd_ble_gatts_hvx(m_conn_handle, &hvx_params);
if (err_code != NRF_ERROR_INVALID_STATE && err_code != BLE_ERROR_GATTS_SYS_ATTR_MISSING) {
APP_ERROR_CHECK(err_code);
}

The problem typically appears on small timer period (I tested for 100 ms), when I reset central app. What is wrong here?

RE: How to check when the stack is ready to send notification?

Anders Strand — Tue, 13 Oct 2015 13:45:30 GMT

Hey.

Starting timer: You can check the BLE_GATTS_EVT_WRITE event to see when the cccd is written to 1 (Notifications enabled). Check the p_ble_evt->evt.gatts_evt.params.write.handle value. If this is the cccd handle of your characteristic, this means notifications are enabled. This is a good trigger to start sending data, because it means that the central is ready to receive notifications.
Stopping timer: You can check cccd writes here as well, to see if notifications are disabled. You should also stop on the event: BLE_GAP_EVT_DISCONNECTED