[Bug]: ANZ433 and MY433 regions allow frequency outside the permitted range

[NomDeTom]

Category

Other

Hardware

Other

Is this bug report about any UI component firmware like InkHUD or Meshtatic UI (MUI)?

• Meshtastic UI aka MUI colorTFT
• InkHUD ePaper
• OLED slide UI on any display

Firmware Version

???

Description

In #7036 the ANZ433 range was added, which changed the tx power limits. I note that it states the lower frequency bound (433.05) correctly, but it allows 8 frequency slots in the range, starting at 433.00 (edge of slot, below the permitted range) which takes it to 434.875 (centre frequency) which is 435.00 (edge of slot) and over 434.79, which is the upper limit.

If the correct range is used, there should only be 6 slots.

Relevant log output

[NomDeTom]

@fifieldt is this because the other 433 band ones were based off the bugged eu433 band?

[fifieldt]

Help me understand, oh great @NomDeTom :)

ANZ_433 is new enough we can fix it. MY_433 is before my time. When I checked EU_433, it looked like the values in the code did not match the legal documents and so I understood it to be wrong.

I just read freq_start, freq_end and assumed the start and end values of the range were the appropriate ones, and the code would do all the relevant slot things.

[NomDeTom]

@fifieldt I tried tracking down how it is used, but it is packaged up and sent away pretty quickly. I'm away from my hardware right now, and I'm not sure if the frequency range that the android app uses is even real.

I'll try and look at it this weekend.

[fifieldt]

Looking at the code ...

RDEF(ANZ_433, 433.05f, 434.79f, 100, 0, 14, true, false, false),


bw = (myRegion->wideLora) ? 812.5 : 250;

uint32_t numChannels = floor((myRegion->freqEnd - myRegion->freqStart) / (myRegion->spacing + (bw / 1000)));


 uint32_t numChannels = floor((434.79f - 433.05f) / (0 + (250 / 1000)))

so numChannels should be 6 ... but due to bw and 1000 both being ints, it's not?

need a log to check

[fifieldt]

INFO  | 00:59:47 0 Radio freq=434.425, config.lora.frequency_offset=0.000
INFO  | 00:59:47 0 Set radio: region=ANZ_433, name=LongFast, config=0, ch=5, power=14
INFO  | 00:59:47 0 myRegion->freqStart -> myRegion->freqEnd: 433.049988 -> 434.790009 (1.740021 MHz)
INFO  | 00:59:47 0 numChannels: 6 x 250.000kHz
INFO  | 00:59:47 0 channel_num: 6
INFO  | 00:59:47 0 frequency: 434.424988

[fifieldt]

so

6 * 250kHz < 1.74 MHz

so it should be OK

weird that it sets

433.049988

rather than

433.05

[fifieldt]

@NomDeTom , where are you seeing 8 slots?

[fifieldt]

Fixed by meshtastic/Meshtastic-Android#2466

[fifieldt]

@danditomaso @garthvh - if you get a moment, could you do a quick check of the algorithm that calculates the number of slots for a given frequency in web and ios? We found a discrepancy between the firmware and Android for ANZ_433 (6 vs 8).

This appears to get the correct result:

numChannels = floor((myRegion->freqEnd - myRegion->freqStart) / (myRegion->spacing + (bw / 1000)));

Will close this firmware issue assuming there is no bug in either :)