[SOLVED] RTT poll rate ?

gahelton1959 · Jan 3rd 2020, 3:49pm

How often does J-Link poll the RTT Control Block Structure to determine if there is new data available ? I have seen information to suggest that "Up" buffers should be sized to accept the amount of data that target can produce for somewhere between 100uS to 1mS; although, I can't seem to find where I read this now.

Here are a few questions that I have.

1. Does this mean that the J-Link checks for new data available in the target buffers somewhere between 100uS and 1mS ? Or the J-Link poll rate faster or slower than that ?
2. How does the J-Link determine if new data is available ? Does it check the ring buffer pointers in the RTT Control Block to see if the target has written new data to the buffer(s) ?

Thanks.

SEGGER - Nino · Jan 6th 2020, 2:43pm

Hi,

Thank you for your inquiry.

1: I assume that with that values you mean the ones from our RTT page: segger.com/products/debug-prob…about-real-time-transfer/
These do not refer to the polling rate from J-Link though but to the the write rate of the target device and the table shows the recommended minimum buffer sizes.
The polling rate of J-Link depends on to many factors to be able to give an exact answer but it is generally somewhere in the lower sub 100 µs area depending on the workload the J-Link has to handle for other tasks.

A more accurate representation is the maximum achievable data transfer speed to the host PC which is roughly 2.2 MB/s as you can see on the RTT site.

2: That is exactly how J-Link determines the buffer state.

Best regards,
Nino

[SOLVED] RTT poll rate ?

[SOLVED] RTT poll rate ?

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