Go to advanced search

by John Westlake
Wed Oct 31, 2018 10:58 pm
Forum: Compute Module
Topic: Expandable baseboard (slot system) for CM3
Replies: 28
Views: 4669

Re: Expandable baseboard (slot system) for CM3

That's brilliant news that someone is working with the dual framebuffer beta testing - sadly software is well beyond my skills. Will your board be available for sale? I'm really keen on adding a display panel on the DPI port for the products "Front Panel" interface / user controls and still have HDM...
by John Westlake
Wed Oct 31, 2018 9:39 pm
Forum: Compute Module
Topic: Expandable baseboard (slot system) for CM3
Replies: 28
Views: 4669

Re: Expandable baseboard (slot system) for CM3

Very nice work :) Are you running two independent displays (two frame buffers) on a single CM3? - if so how are they interfaced?

Again, nice to see such professional design work :)
by John Westlake
Tue Oct 09, 2018 4:48 pm
Forum: Compute Module
Topic: USB [LAN9514I] Enumeration Issue in Compute Module 3L Custom Carrier Board
Replies: 14
Views: 908

Re: USB [LAN9514I] Enumeration Issue in Compute Module 3L Custom Carrier Board

Sorry, I don't work for raspberry pi so cannot publish a raspberry pi reference design (I'm a retired Engineer). I've looked at your PCB design and it does not look too badly designed at all (from what I can tell from PDF overlays) - I'm struggling to understand what the issue could be - I really ne...
by John Westlake
Mon Oct 08, 2018 10:35 am
Forum: Compute Module
Topic: USB [LAN9514I] Enumeration Issue in Compute Module 3L Custom Carrier Board
Replies: 14
Views: 908

Re: USB [LAN9514I] Enumeration Issue in Compute Module 3L Custom Carrier Board

Very odd - have you tried with the ESD protection removed? I have full tools here in my lab to diagnose USB issue (including TDR) - if you want I'd be happy to diagnose your PCB if you can send one to me (with just the USB section built ok) - I'm located in the Czech Rep. I'm pretty sure I'd be able...
by John Westlake
Sun Oct 07, 2018 11:41 am
Forum: Compute Module
Topic: USB [LAN9514I] Enumeration Issue in Compute Module 3L Custom Carrier Board
Replies: 14
Views: 908

Re: USB [LAN9514I] Enumeration Issue in Compute Module 3L Custom Carrier Board

I cannot open your PCB layouts - can you post them as PDF files? Also, I'm not sure if its normal to see USB OTG messages (Maybe it IS normal), but a thought occurs to me - have you tied the CM3 USB OTGID pin to ground (CM3 Pin 168)? Pin 168 should be grounded. "The BCM283x USB port is On-The-Go (OT...
by John Westlake
Thu Oct 04, 2018 4:35 pm
Forum: Compute Module
Topic: USB [LAN9514I] Enumeration Issue in Compute Module 3L Custom Carrier Board
Replies: 14
Views: 908

Re: USB [LAN9514I] Enumeration Issue in Compute Module 3L Custom Carrier Board

@John Westlake: Sir we have tried adding up pull-up on the PRTCTL2 pin but there is no change , the bug is not resolved. Can you show us your PCB layout? Might be worth confirming your 25MHz Clock frequency, 33pf seems like a large crystal loading (depends on the crystal Spec) - if you don't have a...
by John Westlake
Mon Oct 01, 2018 9:40 pm
Forum: Compute Module
Topic: USB [LAN9514I] Enumeration Issue in Compute Module 3L Custom Carrier Board
Replies: 14
Views: 908

Re: USB [LAN9514I] Enumeration Issue in Compute Module 3L Custom Carrier Board

Can you show us your PCB layout? Might be worth confirming your 25MHz Clock frequency, 33pf seems like a large crystal loading (depends on the crystal Spec) - if you don't have an accurate Frequency counter then try reducing the Crystal loading caps to say 18pF Best location to measure the clock is ...
by John Westlake
Mon Oct 01, 2018 8:33 pm
Forum: Compute Module
Topic: LAN9514
Replies: 23
Views: 1132

Re: LAN9514

To improve your Ground "decoupling path" you can simply Ground pins 29, 30 & 32 - this gives you a tight direct Ground connection to the two local PSU decoupling capacitors.

We Ground these pins on our designs....
by John Westlake
Sun Sep 30, 2018 6:22 pm
Forum: Compute Module
Topic: USB [LAN9514I] Enumeration Issue in Compute Module 3L Custom Carrier Board
Replies: 14
Views: 908

Re: USB [LAN9514I] Enumeration Issue in Compute Module 3L Custom Carrier Board

I wonder if your issue is related to the Over Current (OC) protection arrangement you've used - I seem to recall that the LAN9514 supports various software defined OC operating modes. You have configured your device with individual Port current protect which is not the default hardware and 'Software...
by John Westlake
Sun Sep 30, 2018 5:28 pm
Forum: Compute Module
Topic: SDIO on CM3
Replies: 3
Views: 320

Re: SDIO on CM3

Broadcom may have the interface locked to be compatible with only the 4GB eMMC on the CM3, so as to prevent individuals from rolling their own eMMC boot devices. We use a 16GB eMMC with the CM3Lite..... and have used bigger devices on the lab bench - so I can answer that its not "Locked" to 4GB dev...
by John Westlake
Fri Sep 28, 2018 3:57 am
Forum: Compute Module
Topic: LAN9514
Replies: 23
Views: 1132

Re: LAN9514

Apart from the PCB layout need to be take care, does this “undocumented mode of operation” need any software changes to support it? Thanks. I really cannot recommend using the LAN9514 in this way - its undocumented by Microchip for a reason as I went into some length to explain... As others have al...
by John Westlake
Wed Sep 26, 2018 9:55 pm
Forum: Compute Module
Topic: LAN9514
Replies: 23
Views: 1132

Re: LAN9514

The “undocumented mode of operation” is related to reducing the total power consumption and heat dissipation of the LAN9514 – but at the potential expense of performance. Essentially, the LAN9514 internal 3.3V to 1.8V LDO’s that power the USB PLL, LAN PLL circuits and Cores are externally powered fr...
by John Westlake
Tue Sep 25, 2018 2:46 pm
Forum: Compute Module
Topic: I2C Problems on SDA
Replies: 42
Views: 1550

Re: I2C Problems on SDA

at the second image that he posted, the rise time was give a take 1-2us. And that value is at the high side for a I2C bus. Yes, I was thinking about that. certainly seems borderline, and this might help explain why performance improves when pull up R is reduced (faster rise times). But it is not th...
by John Westlake
Mon Sep 24, 2018 6:18 pm
Forum: Compute Module
Topic: I2C Problems on SDA
Replies: 42
Views: 1550

Re: I2C Problems on SDA

You clk is reasonable low 50kHz. And I expect that your probe is 10:1, and this should normally not be a issue. Don't confuse Data rate with Edge speeds, sure I2C Data rate is slow, but its edge speed can be measured in nS... the fact that probe loading and series termination resistors are affectin...
by John Westlake
Mon Sep 24, 2018 4:46 pm
Forum: Compute Module
Topic: I2C Problems on SDA
Replies: 42
Views: 1550

Re: I2C Problems on SDA

If we are lucky added a couple of 100nF directly across Pin 1 - Pin 28 and Pin 27 - Pin 28 will resolve the problem ... fingers crossed Sadly this didn't change the situation :( But thanks for pointing it out, I'll definitely fix those caps on the next board! Another observation: if I remove the sc...
by John Westlake
Sat Sep 22, 2018 7:59 pm
Forum: Compute Module
Topic: I2C Problems on SDA
Replies: 42
Views: 1550

Re: I2C Problems on SDA

Cirrus Logic now Co. owns one of my Patents when they bought out Wolfson... Interesting about Cirrus Logic, what was your patent for? Gosh, IIRC it was a method to limit the Modulation index of a Class D Feedback system.... Keeping the Modulator well behaved during extremes of modulation... it was ...
by John Westlake
Sat Sep 22, 2018 3:59 pm
Forum: Compute Module
Topic: I2C Problems on SDA
Replies: 42
Views: 1550

Re: I2C Problems on SDA

Ok, maybe we have been looking at this all wrong, looking at your PCB design and I cannot see from the Low Res Picture any High Frequency PSU decoupling near the Digital PSU pin DBVDD - you could try placing a 100nF High Quality (= Low Inductance) Ceramic capacitor DIRECTLY across Pin 1 DBVDD and Pi...
by John Westlake
Sat Sep 22, 2018 3:23 pm
Forum: Compute Module
Topic: I2C Problems on SDA
Replies: 42
Views: 1550

Re: I2C Problems on SDA

Might be worth a shot, but they don't have that note listed next to the control interface SDIN, SCLK (I2C) pins. I already have MODE and CSB externally pulled low. My bad, re-reading the Datasheet and the Pull-up refers to the mode select Pins themselves not the actual SDA/SCL pins....! Shame, it w...
by John Westlake
Sat Sep 22, 2018 3:11 pm
Forum: Compute Module
Topic: I2C Problems on SDA
Replies: 42
Views: 1550

Re: I2C Problems on SDA

Reading the Wolfson Datasheet and the 2 Wire interface is described as a 2-wire MPU serial interface with NO mention of I2C so I would suspect I2C 'like' but not necessarily 100% I2C compatible I was wondering about this. But it might also be a licensing thing. Yes, I suspect it might be, everyone ...
by John Westlake
Sat Sep 22, 2018 1:56 pm
Forum: Compute Module
Topic: I2C Problems on SDA
Replies: 42
Views: 1550

Re: I2C Problems on SDA

Reading the Wolfson Datasheet and the 2 Wire interface is described as a 2-wire MPU serial interface with NO mention of I2C so I would suspect I2C 'like' but not necessarily 100% I2C compatible.... "The WM8731/L supports a 2-wire MPU serial interface. " Might be a clue here in this control register ...
by John Westlake
Fri Sep 21, 2018 4:02 pm
Forum: Compute Module
Topic: I2C Problems on SDA
Replies: 42
Views: 1550

Re: I2C Problems on SDA

Also, notice the Ground floor modulation one clock period proceeding and reasserts slightly post the successful ACK - I wounder if this is telling us anything? It really does look like some kind of pull-up is being released one clock period prior to the successful ACK.
by John Westlake
Fri Sep 21, 2018 3:57 pm
Forum: Compute Module
Topic: I2C Problems on SDA
Replies: 42
Views: 1550

Re: I2C Problems on SDA

Thanks for this info. Removing pull-ups I can still see some activity on SDA and SCL, but not really spikes. I thought I read that GPIO 2 and 3 have weak internal (50k?) pull-ups, and what I see is in line with that, very slow rise times that do not make thresholds. So I don't know if it is an acti...
by John Westlake
Fri Sep 21, 2018 12:10 am
Forum: Compute Module
Topic: I2C Problems on SDA
Replies: 42
Views: 1550

Re: I2C Problems on SDA

I'm not saying this is the case here - But I've seen IC's that use Active drive (Active pull-up) 'Open Drain' outputs for a very brief period to allow a faster edge (due to the Low impedance drive) - after this brief edge 'period' the outputs resort to standard Open Drain operation - we got caught o...
by John Westlake
Wed Sep 12, 2018 10:05 am
Forum: Compute Module
Topic: SOLVED: LAN9514 Ethernet issue after reboot
Replies: 19
Views: 925

Re: SOLVED: LAN9514 Ethernet issue after reboot

Great you have it working, always hard when your not sure if its a software or hardware issue...
by John Westlake
Sat Sep 01, 2018 1:23 pm
Forum: Compute Module
Topic: SOLVED: LAN9514 Ethernet issue after reboot
Replies: 19
Views: 925

Re: LAN9514 Ethernet issue after reboot

Yep i have a 1MOhm resistor across my 25MHz crystal. I closely based my design on the following document released by microchip: http://ww1.microchip.com/downloads/en/DeviceDoc/9514_sch.pdf PS to your PS :D - The crystal is still something that has left me wondering, so it is something i might still...

Go to advanced search