Millett LR + TP Opus + AMB α24 reboot

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jack
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#106 Re: Millett LR + TP Opus + AMB α24 reboot

Post by jack »

Have you 'scoped the power rails?

Screwed up TWI/I2C could easily be the issue here:

SDA & SCL should really have 4K7 pull-ups on them - this is a massive design omission. All TWI-compliant devices are open collector or open-drain and all bets are off without the pull-ups.

Quoting from the ATmega328P data sheet, page 172, section 21.2.2:
21.2.2 Electrical Interconnection
As depicted in Figure 21-1 on page 173, both bus lines are connected to the positive supply voltage through pull-up
resistors. The bus drivers of all TWI-compliant devices are open-drain or open-collector. This implements a wired-AND
function which is essential to the operation of the interface. A low level on a TWI bus line is generated when one or more TWI
devices output a zero. A high level is output when all TWI devices tri-state their outputs, allowing the pull-up resistors to pull
the line high. Note that all AVR® devices connected to the TWI bus must be powered in order to allow any bus operation.
Later, in 21.5.1:
21.5.1 SCL and SDA Pins
These pins interface the AVR TWI with the rest of the MCU system. The output drivers contain a slew-rate limiter in order to
conform to the TWI specification. The input stages contain a spike suppression unit removing spikes shorter than 50ns. Note
that the internal pull-ups in the AVR pads can be enabled by setting the PORT bits corresponding to the SCL and SDA pins,
as explained in the I/O port section. The internal pull-ups can in some systems eliminate the need for external ones.
(my italics)

This is generally not great practice as the internal pull-ups are weak (deliberately) - they are 20K - 50K (section 28.2 of the datasheet) so not great at holding the data lines in case of noise.

Even if this is what they are doing, I would strongly recommend adding a minimum 10K and preferably 4K7 from each of SDA and SCL to Vcc - you can easily test that on the I2C pin header on the board - between each of J4-5 & J4-6 to J4-1.

Further to Nick's comment below, screwed up I2C will cause all sorts of issues like this.
Last edited by jack on Thu Dec 16, 2021 1:01 pm, edited 3 times in total.
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#107 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Nick »

If it's killing the flash then it's very broken. I would look at reset as it may be putting it into HV prog mode or something odd. I was assuming you were just getting reset to start or hangs. Btw. Don't trust the first byte of eeprom unless you have solid reset and shutdown logic in place.
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#108 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

jack wrote: Thu Dec 16, 2021 11:50 am I would strongly recommend adding a minimum 10K and preferably 4K7 from each of SDA and SCL to Vcc - you can easily test that on the I2C pin header on the board - between each of J4-5 & J4-6 to J4-1.

Further to Nick's comment below, screwed up I2C will cause all sorts of issues like this.
It looks as though there are pull-up resistors on the relay boards that J4 interfaces to... here's the schematic of the attenuator board (source select is much the same), see J1 that connects to J4 on the LCDuino with R3 and R4:

Image

R3 and R4 are defined in the parts list as 3.3KΩ, with a note to say "If you will be stacking multiple δ1/δ2 boards, then only one of them needs to have R3, R4 and L1 installed" so I think those are intended to be the pull-ups. The wires connecting the two boards together are not too long, see the 'rainbow' loom going from the processor to the relay stack:

Image
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
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#109 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Nick »

Further to Nick's comment below, screwed up I2C will cause all sorts of issues like this.
Yes, agreed, but not to the point where the processor wont start without a reflash.
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#110 Re: Millett LR + TP Opus + AMB α24 reboot

Post by jack »

Thermionic Idler wrote: Thu Dec 16, 2021 1:13 pm
jack wrote: Thu Dec 16, 2021 11:50 am I would strongly recommend adding a minimum 10K and preferably 4K7 from each of SDA and SCL to Vcc - you can easily test that on the I2C pin header on the board - between each of J4-5 & J4-6 to J4-1.

Further to Nick's comment below, screwed up I2C will cause all sorts of issues like this.
It looks as though there are pull-up resistors on the relay boards that J4 interfaces to... here's the schematic of the attenuator board (source select is much the same), see J1 that connects to J4 on the LCDuino with R3 and R4:

Image

R3 and R4 are defined in the parts list as 3.3KΩ, with a note to say "If you will be stacking multiple δ1/δ2 boards, then only one of them needs to have R3, R4 and L1 installed" so I think those are intended to be the pull-ups. The wires connecting the two boards together are not too long, see the 'rainbow' loom going from the processor to the relay stack:
That would be fine so long as the boards are stacked... still need to look at noise on the power & reset line though...

Are you sure you don't have an I2S address clash anywhere?
Nick wrote: Thu Dec 16, 2021 1:21 pm
Further to Nick's comment below, screwed up I2C will cause all sorts of issues like this.
Yes, agreed, but not to the point where the processor wont start without a reflash.

...hence my comments regarding implementation of reset in noisy environments.

If you have a spare lcduino board, maybe just try that?
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#111 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

jack wrote: Thu Dec 16, 2021 1:31 pm still need to look at noise on the power & reset line though...
I'm suspecting the power line as that's the thing that has undergone major change. The reset line isn't normally connected to anything beyond J3 if I'm not re-flashing the software, so it would only pick up noise from the tracks connecting J3 pin 6 to the processor socket, C3 and reset button. I can't see how there would be any more noise in that location than before, in fact if anything there should be less as there were three power transformers in the chassis near there previously.

Image
jack wrote: Thu Dec 16, 2021 1:31 pm Are you sure you don't have an I2S address clash anywhere?
Yep, the board I2C addresses have remained the same all the time I've had it. Sadly I don't have a spare board.

Thanks to all for the input so far, it's greatly appreciated.
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
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#112 Re: Millett LR + TP Opus + AMB α24 reboot

Post by jack »

A simple test would simply be to put the lcduino back on the old PSU.

Sounds (!) like you need to locate the source of the issue by a process of elimination.

Change one thing and one thing only at a time.
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#113 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

jack wrote: Thu Dec 16, 2021 2:17 pm A simple test would simply be to put the lcduino back on the old PSU.

Sounds (!) like you need to locate the source of the issue by a process of elimination.

Change one thing and one thing only at a time.
That's sort of the plan - putting the actual PSU back is not straightforward as I've taken out the transformers and IEC socket, and replaced it with the 5V inlet - and 5V is not high enough for the regulator to work. And I need to have the battery infrastructure there to power the LR phono that I'll be building and testing over Christmas. I figured that a good way to avoid hum in a phono stage that uses step-up iron and inductors, was to not have any mains transformers nearby to induce it in the first place.

But yes, I'm currently knocking up something in KiCad which will have improved battery monitoring (taking Nick's advice to use a voltage reference and comparitor) and a regulated 5V supply to the LCDuino, which will basically be modelled on the previous supply, just with a 12V DC input voltage instead of rectified AC. This time I'll also make sure to include the flyback diodes!
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
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#114 Re: Millett LR + TP Opus + AMB α24 reboot

Post by jack »

You can get cheap single chip power management ICs (PMICs) from TI and others.

They're really very nice.
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#115 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Nick »

Just try shorting the j6 to that cap to the reset pin to ground. At least that will see if its the problem. Supply line noise should be being fixed by the decoupling caps on all the processor supply inputs. That reset pin looks to me very much like an antenna that's sitting there looking for HF noise and injecting it directly into the reset pin of the processor.

I know from getting atmel processors to cope with ESD testing, any and all external lines into the processor need to be actively clamped with protection circuits.
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#116 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

Thanks Nick - I looked at the AMB forums and I've seen posts elsewhere from people who've seen a benefit from shorting the reset switch out with a small cap - which is exactly the same as shorting pin 6 to ground as C3 becomes the small cap in question. I've included that in my cunning plan.
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
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#117 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

All done with work until 10th January - so it's time to start the LR phono project build.

Opening ceremony completed - a picture of the empty PCB and a playout of "What's he building in there?".

(My vinyl copy of Mule Variations arrived today, apparently the current reissue doesn't sound very good so I searched out an original first pressing - which sadly wasn't cheap).

Image
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
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#118 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Dave the bass »

.... "what's he building in there....." ... :shock: :)
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#119 Re: Millett LR + TP Opus + AMB α24 reboot

Post by Thermionic Idler »

Dave the bass wrote: Thu Dec 23, 2021 3:21 pm .... "what's he building in there....." ... :shock: :)
Eventually it should look like this:

Image

At the end of today's session, mine looked like this:

Image

More tomorrow.
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
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#120 Re: Millett LR + TP Opus + AMB α24 reboot

Post by IslandPink »

Pete's what you call a stalwart. Lovely fella, met him in 2005 at ETF.
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