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+--- Thread: PWM whine near earpiece in low signal phone call and loud sound sent to the other end (/showthread.php?tid=13922)
RE: PWM whine near earpiece in low signal phone call and loud sound sent to the other end - dsimic - 06-11-2021
(06-10-2021, 02:01 PM)vortex Wrote:(06-04-2021, 09:26 AM)dsimic Wrote: I might be wrong, bit I think that at least some of the weird noises I've described above were caused by the voice of the called party being played through the PinePhone's built-in speaker. That surely created an audio spill, which at least contributed to those weird pulsating noises.
Could an audio spill be one of the reasons for the original problem you're experiencing? If so, something inside the phone could be picking up the audio output signal and emitting it, in some way or form, through the built-in speaker. The microphone could be picking that, creating a spill.
I had originally dismissed this possibility, but the two of you convinced me I had prematurely dismissed it and should actually test it. So I did two phone calls where I turned the earpiece speaker volume all the way to zero so that there would be no audio spill except via RF pickup in the earpiece speaker and then producing sound.
On a 4G call (I think it was 4G, but it might have been 3G), there were no problems. The recording was nice and quiet and the frequency comb was not there as seen in the spectrogram below.
However, in a call with a worse signal and on 2G, the frequency comb is still there as seen by the spectrogram below.
From this, I think there is an issue independent of audio spill. Now, that isn't to say that audio spill couldn't also be a problem with a similar fequency comb and just adding more noise on top. But, there is definitely at least something there that isn't audio spill.
Thank you for doing this additional testing! Based on the test results, I agree it's safe to conclude that the root cause of the issue isn't an audio spill. In the above-described tests, the issue was clearly demonstrated to be caused by changing the network access type and the strength of network reception, while the audio spill was completely ouf of the equation.
(06-10-2021, 02:01 PM)vortex Wrote:(06-04-2021, 09:26 AM)dsimic Wrote: Sorry, I wasn't clear enough... The above-linked repository contains the latest version of the official, proprietary modem firmware, which is provided by Quectel. It would be advisable to update the modem firmware to the latest available official version; just have a look at the mile-long update release notes.
I see I misunderstood you. I probed the modem and I am definitely running some version of the EG25GGBR07A08M2G firmware, but it is possible I am not running the very latest version of it. I am going to try to update it to this version for some next tests and see if that does anything. Hopefully I can do this soon, but I have been a bit busy lately.
As a note, the latest available version of the proprietary modem firmware should be EG25GGBR07A08M2G_01.002.01.002.
RE: PWM whine near earpiece in low signal phone call and loud sound sent to the other end - vortex - 07-18-2021
I got side tracked for a while and wasn't able to work on this for a while. I just flashed the very latest modem firmware to make sure that it is the newest and ran the tests again.
This time, I upgraded the analysis and plotting code to make a fourth subplot that zooms in on the first peak of the frequency comb and increased the default number of samples per segment by 16 times to better resolve the peak. The code also lets one see the plot in a matplotlib gui, which makes it easier for anyone wanting to inspect it closely. The spectrogram is below
![[Image: Freja_Nordsiek_2021_07_18_2G_call_latest...rmware.png]](https://raw.githubusercontent.com/frejanordsiek/pinephone_call_noise_investigation/main/plots/Freja_Nordsiek_2021_07_18_2G_call_latest_modem_firmware.png)
The frequency comb is still there, unfortunately.
With the new subplot and the higher frequency resolution, the frequency comb's base frequency appears to be about 216.65 Hz and is about 0.5-1.0 Hz wide.
RE: PWM whine near earpiece in low signal phone call and loud sound sent to the other end - mouffa - 07-19-2021
have a look at the AT commands manual Chapter 12 (Audio Commands), there are various parametres to be configured, I have the latest version (2.0 - 24/02/2021) of the manual which is very extensive
12 Audio Commands ............................................................................................................................ 227
12.1. AT+CLVL Loudspeaker Volume Level Selection ................................................................ 227
12.2. AT+CMUT Mute Control ...................................................................................................... 228
12.3. AT+QAUDLOOP Enable/Disable Audio Loop Test ............................................................. 229
12.4. AT+VTS DTMF and Tone Generation ................................................................................. 229
12.5. AT+VTD Set Tone Duration................................................................................................. 231
12.6. AT+QAUDMOD Set Audio Mode ........................................................................................ 232
12.7. AT+QDAI Digital Audio Interface Configuration .................................................................. 233
12.8. AT+QEEC Set Echo Cancellation Parameters ................................................................... 235
12.9. AT+QSIDET Set the Side Tone Gain in Current Mode ....................................................... 236
12.10. AT+QMIC Set Uplink Gains of Microphone ........................................................................ 237
12.11. AT+QRXGAIN Set Downlink Gains of RX .......................................................................... 237
12.12. AT+QIIC Read and Write Codec via IIC ............................................................................. 239
12.13. AT+QTONEDET Enable/Disable DTMF Detection ........................................................... 240
12.14. AT+QLDTMF Play Local DTMF .......................................................................................... 241
12.15. AT+QWDTMF Play or Send DTMF Files to Far End .......................................................... 242
12.16. AT+QLTONE Play a Local Customized Tone ..................................................................... 243
12.17. AT+QAUDRD Record Media File ........................................................................................ 245
12.18. AT+QPSND Play WAV File ................................................................................................. 247
12.19. AT+QTTS Play Text ............................................................................................................ 248
12.20. AT+QTTSETUP Set TTS .................................................................................................... 250
12.21. AT+QWTTS Play Text or Send Text To Far End ................................................................. 251
12.22. AT+QAUDCFG Query and Configure Audio Tuning Process ............................................. 253
12.22.1. AT+QAUDCFG="alc5616/dlgain"
Set the Downlink Gain Level for Codec
ALC5616…… .............................................................................................................................. 253
12.22.2. AT+QAUDCFG="alc5616/ulgain" Set the Uplink Gain Level for Codec ALC5616 ... 254
12.22.3. AT+QAUDCFG="tonevolume" Set the Tone Volume ................................................ 255
12.22.4. AT+QAUDCFG="alc5616/pwrctr" Enable/Disable the Power Reset ........................ 256
12.22.5. AT+QAUDCFG="nau8814/dlgain" Set the Downlink Gain Level for Codec NAU8814…................................................................................................................................ 257
12.22.6. AT+QAUDCFG="nau8814/aoutput" Set the Analog Output for Codec NAU8814 ... 258
12.22.7. AT+QAUDCFG="encgain" Set Uplink ENC Gains ................................................... 259
12.22.8. AT+QAUDCFG="voltedtmfcfg" Set Duration and Volume of VoLTE DTMF Tone .... 260
12.22.9. AT+QAUDCFG="decgain" Set Downlink DEC Gains ............................................... 261
12.22.10. AT+QAUDCFG="fns" Enable/Disable Noise Suppression ................................ 262
12.22.11. AT+QAUDCFG="nau8810/config" Set Register Value of Codec NAU8810 ............. 263
12.23. AT+QAUDPLAY Play Media File ........................................................................................ 264
12.24. AT+QAUDPLAYGAIN Set Audio Playing Gain ................................................................... 265
12.25. AT+QAUDRDGAIN Set Audio Recording Gain .................................................................. 266
12.26. AT+QACDBLOAD Write ACDB File .................................................................................... 267
RE: PWM whine near earpiece in low signal phone call and loud sound sent to the other end - dsimic - 07-28-2021
A few days ago, one community member complained on the #pinephone IRC channel about having some kind of weird interference on his PinePhone, during a 2G voice call. After some debugging, which included changing the audio-related modem settings through some of the above-listed AT commands (with no success), we came to a conclusion that we need a weird approach: let's make the modem antenna larger.
With that mod in place, signal strength (as reported by the "AT+CSQ" command) went up from around -100 dBm, which is considered poor, to around -70 dBm, which is considered very good, and no interference was present during a voice call. Thus, I'd suggest that you try something similar, just to verify whether the issues are caused by the network and low signal strength. Of course, improving the modem antenna is nowhere nearly as easy as sticking a randomly shaped piece of aluminum foil to the back cover, but that's all just for the purpose of testing.
The attached picture shows what the "early prototype" looked like.
RE: PWM whine near earpiece in low signal phone call and loud sound sent to the other end - mouffa - 07-29-2021
I thought down there was the Wifi/BT antenna and the 3 antennae on the top were for the modem.
RE: PWM whine near earpiece in low signal phone call and loud sound sent to the other end - mouffa - 07-29-2021
I believe with a good tuning of the modified antenna you could achieve very strong signal, you could use thin wires, do some theoretical or simulated calculations and in the end microadjust with an oscilloscope or something like this
RE: PWM whine near earpiece in low signal phone call and loud sound sent to the other end - vortex - 08-14-2021
(07-28-2021, 10:27 AM)dsimic Wrote: A few days ago, one community member complained on the #pinephone IRC channel about having some kind of weird interference on his PinePhone, during a 2G voice call. After some debugging, which included changing the audio-related modem settings through some of the above-listed AT commands (with no success), we came to a conclusion that we need a weird approach: let's make the modem antenna larger.
With that mod in place, signal strength (as reported by the "AT+CSQ" command) went up from around -100 dBm, which is considered poor, to around -70 dBm, which is considered very good, and no interference was present during a voice call. Thus, I'd suggest that you try something similar, just to verify whether the issues are caused by the network and low signal strength. Of course, improving the modem antenna is nowhere nearly as easy as sticking a randomly shaped piece of aluminum foil to the back cover, but that's all just for the purpose of testing.
The attached picture shows what the "early prototype" looked like.
Not surprised that the AT commands didn't work since sound stuff on the modem end is way after the microphone. Though AT commands affecting the power systems in the modem might have an effect.
That antenna modification is clever. Makes sense that it helped. Modem is less likely to drop to 2G and crank up the transmit power in a burst fashion.
I am going to try that.
(07-29-2021, 05:24 AM)mouffa Wrote: I thought down there was the Wifi/BT antenna and the 3 antennae on the top were for the modem.
I've tried to look for diagrams of which antenna is which and have not found any. So I don't know. In fact, I don't even know if the whole thing at the bottom is one antenna or two (no information on whether the left most antenna piece is connected electrically to the others).
Anyhow. If the modification was on the right antenna, that is a nice simple work around. If it is the wrong antenna, while it is still a nice work around, the fact it works would imply that there is some interference going on between the different antennas which is a larger problem (adding metal to the wrong antenna
RE: PWM whine near earpiece in low signal phone call and loud sound sent to the other end - eugenr - 01-07-2022
The microphone is definitely pickup noise when the modem is working -- like mobile data activity or in a call.
Easy to detect/record that by making sure you are using only 4G mobile data (i.e. disable Wifi). Then prepare the microphone for capture in alsamixer and increase the Mic1 Boost to maximum so to easier hear the modem noises.
Record the microphone using arecord (alsa-utils package):
arecord -f cd -V mono test.wav
(use Ctrl-C to terminate. Play back with: aplay test.wav for example)
During recording, whenever I use mobile data, the "RF noises" are recorded. Also when I do a voice call.
Can we (better) isolate/shield the microphone line/cable? Is there analog audio signal going on from the microphone (at the bottom of the phone) to the mainboard (at top)? I'm going to check these things out.
RE: PWM whine near earpiece in low signal phone call and loud sound sent to the other end - eugenr - 01-07-2022
I've opened the phone (mine is Mobian Edition 2/16GB) and did some experiments confirming that the modem antenna system is interfering with the microphone when the modem does work.
When I disconnected the antenna black cable the modem had no network signal. But I've successfully use the Wifi antenna cable from my laptop (had to opened it too) that I've connected to ANT_MAIN near the modem ( c2 as used here: https://forum.pine64.org/showthread.php?tid=15474 ).
So with the modem getting the signal using my laptop's Wifi antenna (instead of the phone's bottom antenna), the microphone worked great -- no "digital" noise whatsoever (voice calls or mobile data usage).
It doesn't seem to me to be an easy solution to fix this. There are some possibilities that I'm imaging:
- Pine64 to come up with another USB-C board and/or the plastic frame with printed antennas that doesn't affect the microphone.
- me to make a custom antenna and place it maybe between the battery and the back cover or on the side ...
- don't know... any ideas?
Until then, I'll continue to use the mic without boost (level at 0). The noises are gone, but the sound volume is very low and some people struggle hearing me.... Recording sounds is pretty useless like this too.
RE: PWM whine near earpiece in low signal phone call and loud sound sent to the other end - eugenr - 01-14-2022
The interfering noise disappears when I touch the bottom printed antenna just above the microphone hole (with the phone facing down). It is enough to firmly touch it with a finger or a short wire or loop.
But that seems to negatively affects the antenna's performances as reported by AT+CSQ command. That returns the received signal strength. Without touching the antenna, I get a value of 14, which is reduced to 10 when touching -- which means the received signal is weaker.
Since the transmitting signal is the one interfering with the mic, I'll search for a way to make it weaker from the modem, instead of messing the antenna...