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cc2538: fix RSSI offset #14672

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Merged
merged 1 commit into from
Aug 3, 2020
Merged

cc2538: fix RSSI offset #14672

merged 1 commit into from
Aug 3, 2020

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jia200x
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@jia200x jia200x commented Jul 31, 2020

Contribution description

This PR fixes the offset for the RSSI calculation of CC2538 radios and removes an RFCORE_ASSERT that checks that the internal RSSI value is greater than the sensitivity.

The latter produced crashes while testing #14655 when measured values of RSSI were below the RX sensitivity (-97 dBm).

Also according to the Reference Manual, section 23.10.3, the actual power of the reception is calculated with the RSSI register and the RSSI offset (-73).

Testing procedure

Check the RSSI values when receiving data.

Issues/PRs references

Fixes the crash in #14655

@jia200x jia200x requested review from maribu and PeterKietzmann July 31, 2020 15:02
@jia200x jia200x requested review from fjmolinas and smlng as code owners July 31, 2020 15:02
@PeterKietzmann PeterKietzmann added Area: drivers Area: Device drivers Type: bug The issue reports a bug / The PR fixes a bug (including spelling errors) labels Jul 31, 2020
@maribu
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maribu commented Jul 31, 2020

Also according to the Reference Manual, section 23.10.3, the actual power of the reception is calculated with the RSSI register and the RSSI offset (-73).

In that section no offset is given, it says "For example, with an offset of 73 [...]". It also says "See the datasheet for the correct offset value to use."...

To me, it is not clear what the correct value now actually is.

@PeterKietzmann
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The datasheet (Sect. 5.12 RSSI/CCA Characteristics) gives an RSSI/CCA offset of 73dBm and the formula to calculate RealRSSI= Registervalue– offset. We do that here using CC2538_RSSI_OFFSET (=-73dBm) already. ACK from my side

@PeterKietzmann PeterKietzmann added the CI: ready for build If set, CI server will compile all applications for all available boards for the labeled PR label Aug 2, 2020
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How can RFCORE_ASSERT crash the program (in #14655)? Unfortunately it is not documented, but to me is seems to enable a debug massage and return the function with an error, nothing more than that (see here and here). Regardless of that, removal of the assertion seems valid to me.

I ran some tests using examples/default on an nrf52840dk and a remote-reva locally.

  • txtsend nrf52840dk -> remote-reva (sending with 0dBm).
  • change txpower on nrf52840dk to -20dBm.
  • txtsend nrf52840dk -> remote-reva (repeatedly).

master

  • remote-reva receives packets with RSSI of 21 (@ 0dBm sending)
PKTDUMP: data received:
~~ SNIP  0 - size:   5 byte, type: NETTYPE_UNDEF (0)
00000000  68  65  6C  6C  6F
~~ SNIP  1 - size:  18 byte, type: NETTYPE_NETIF (-1)
if_pid: 3  rssi: 21  lqi: 233
flags: 0x0
src_l2addr: 1B:A5
dst_l2addr: 00:12:4B:00:06:15:A0:04
~~ PKT    -  2 snips, total size:  23 byte
  • remote-reva receives packets with RSSI of -1 (@ -20dBm sending) and prints assertion
RFCORE_ASSERT(rssi_val > CC2538_RF_SENSITIVITY) failed at line 353 in _recv()!
  RFCORE_SFR_RFERRF = 0x00
PKTDUMP: data received:
~~ SNIP  0 - size:   5 byte, type: NETTYPE_UNDEF (0)
00000000  68  65  6C  6C  6F
~~ SNIP  1 - size:  18 byte, type: NETTYPE_NETIF (-1)
if_pid: 3  rssi: -1  lqi: 233
flags: 0x0
src_l2addr: 1B:A5
dst_l2addr: 00:12:4B:00:06:15:A0:04
~~ PKT    -  2 snips, total size:  23 byte

this PR

  • remote-reva receives packets with RSSI of -75 (@ 0dBm sending)
    -> much more reasonable range!
PKTDUMP: data received:
~~ SNIP  0 - size:   5 byte, type: NETTYPE_UNDEF (0)
00000000  68  65  6C  6C  6F
~~ SNIP  1 - size:  18 byte, type: NETTYPE_NETIF (-1)
if_pid: 3  rssi: -75  lqi: 229
flags: 0x0
src_l2addr: 1B:A5
dst_l2addr: 00:12:4B:00:06:15:A0:04
~~ PKT    -  2 snips, total size:  23 byte
  • remote-reva receives packets with RSSI of -97 (@ -20dBm sending) and does not print assertion
PKTDUMP: data received:
~~ SNIP  0 - size:   5 byte, type: NETTYPE_UNDEF (0)
00000000  68  65  6C  6C  6F
~~ SNIP  1 - size:  18 byte, type: NETTYPE_NETIF (-1)
if_pid: 3  rssi: -97  lqi: 229
flags: 0x0
src_l2addr: 1B:A5
dst_l2addr: 00:12:4B:00:06:15:A0:04
~~ PKT    -  2 snips, total size:  23 byte

PeterKietzmann
PeterKietzmann approved these changes Aug 3, 2020
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Although I'm not sure this PR fixes the crash in #14655, my ACK holds for this change.

@PeterKietzmann PeterKietzmann merged commit 6adf07c into RIOT-OS:master Aug 3, 2020
@PeterKietzmann PeterKietzmann mentioned this pull request Aug 3, 2020
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@fjmolinas fjmolinas mentioned this pull request Dec 11, 2020
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@PeterKietzmann PeterKietzmann PeterKietzmann approved these changes

@maribu maribu Awaiting requested review from maribu

@fjmolinas fjmolinas Awaiting requested review from fjmolinas

@smlng smlng Awaiting requested review from smlng

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