sd_ble_gatts_hvx cache

[Stayhungry]

1、how long will it take for me to cache?

Once I call sd_ble_gatts_hvx, assuming tx_queue is large enough, how long can I cache data to softdeivce?

For example, I called sd_ble_gatts_hvx once, and then called again after 5ms. Can I cache successfully,Or the data has been sent out? Why?

2、Cached data and the size of the actual packet sent

If ATT_MTU is set to 247, LL payload = 251, tx_queue = 2, should I get NO_RESOURCE once if I call sd_ble_gatts_hvx(buffer, buffer len = 100) third times ?

This time actually sent the package which payload len = 200byte?

Thanks

[endnode]

1. How long? Doesn't make sense. Tx queue size is partially configurable in Nordic Soft Device and how much time it takes to flush it over BLE that's impossible to say as it depends on how BLE connection link performs at that moment (what is the interval, what is packet loss etc.) So forget about time, there is no guaranteed time when it comes to radio like BLE.
2. Tx queue size in Nordic Soft Device should have "slots" so on (G)ATT layer it can hold certain number of packets regardless the size. So you can get BLE_ERROR_NO_TX_BUFFERS error code in response if you try to push some more outgoing packets but there is no available Tx slot on (G)ATT layer in the SD. The size doesn't matter.

[Stayhungry]

Thanks,endnode.

If ATT_MTU = 23, ignoring packet retransmission, if the connection interval is 50ms, tx_queue is large enough and the MCU is running at the beginning of interval

When I call sd_ble_gatts_hvx (buffer, buffer len = 20) continuously for 3 times within 10ms, then delay 5ms for other processes to run, then call sd_ble_gatts_hvx (buffer, buffer len = 20) 3 times within 10ms, Is it possible to send 6 pakcets in a connection event?

If ATT_MTU = 23, tx_queue = 3

Case 1, I call in a row: sd_ble_gatts_hvx (buffer, buffer len = 20), sd_ble_gatts_hvx (buffer, buffer len = 10), sd_ble_gatts_hvx (buffer, buffer len = 8), sd_ble_gatts_hvx (buffer, buffer len = 15),

Case 2, I call in a row: sd_ble_gatts_hvx (buffer, buffer len = 20), sd_ble_gatts_hvx (buffer, buffer len = 20), sd_ble_gatts_hvx (buffer, buffer len = 20), sd_ble_gatts_hvx (buffer, buffer len = 20),

I think the two cases of the fourth call sd_ble_gatts_hvx will return BLE_ERROR_NO_TX_BUFFERS, the result is that I send packets in both a connection event number is 3, but the total length of the data sent is not the same, may I ask Understand right? If my understanding is correct, I have to consider the buffer len for each call to sd_ble_gatts_hvx for optimal throughput