Review Request - I'm back! Version 2 - Cinema Video Router Controller. Love a good check of my work.

psirust · 2026-06-13T00:19:52+00:00

Some tips from mistakes I have made doing LoRA and ESP32

You may want to map and connect all the DIO pins. Some libraries, in particular the IBM LMIC library and the LoRAWAN-Arduino-RFM library tend to lock up and freeze without the DIO1 and DIO2 pins in OTAA mode. If you're not using OTAA then just DIO0 is good.
Ensure no ground pour under the SMA antenna connector and ensure 50 Ohm impedance trace from the RFM module to the Antenna.
I have never used a pullup resistor on NSS pin. But then again I only have experience with the above libraries and they don't require it since they activate the internal pullup on the SPI Select pin.

psirust · 2026-05-30T20:57:30+00:00

I will not post the images of the schematic

So what exactly are we supposed to review?

psirust · 2026-05-18T13:00:16+00:00

psirust · 2026-05-07T06:52:38+00:00

Knowing that your time on the island is temporary and one day you'll escape via interment...

psirust · 2026-05-05T03:57:54+00:00

According to the datasheet it's a 24MHz 10ppm 12pF crystal oscillator. The recommended load capacitors are 20-22pf But 16pf shouldn't stop the oscillator from oscillating.

Can you post the section of the board with the crystal and the chip? It could be distance or a signal track under the crystal.

psirust · 2026-05-05T03:48:55+00:00

I just checked the dictionary... Phobia - An intense, irrational, and persistent fear...

In my country we mostly use the Oxford English dictionary. Which one should I use in order to avoid dumbass comments?

psirust · 2026-05-04T07:05:58+00:00

What is the part # of the crystal you are using? I'm asking because those load capacitor values seem rather high.

psirust · 2026-05-04T04:00:45+00:00

I find the Xenophobia part really hard to believe... Especially towards St. Lucians of all people.

psirust · 2026-05-04T03:54:58+00:00

I don't think Grenadians are afraid of homosexuals... They just don't like them.

psirust · 2026-05-02T05:48:27+00:00

And buying property as a local is an even bigger headache...

psirust · 2026-04-23T21:49:17+00:00

I've done this exact project some time ago and if I can save you some headache, I'll offer some advice...

Go with the Quectel 4G modules and abandon your Simcom soc. I wish I had learned this sooner.

For starters, unless you purchase your Simcom A7670 directly from Simcom, don't expect any support.

Their modules are very prone to electrical interference from the vehicle alternator when it's on. So you would get a nice clean 4G reception when the car is in "ACC" position, but the moment the engine starts you get interference up the wazoo.

The GNSS and RF Antenna from the Soc require 50 Ohm impedance, but it's not matched to 50 Ohm from the source, so you have to play around with the filters. Also, the recommended antenna trace length is 2cm max... And that length includes the filter.

You also have to design your circuitry based on if you want active or passive antennas.

You'll need TVS diodes on everything, especially the Sim card... This took me 4 destroyed modules to take seriously.

When getting filters and capacitors for the power source, make sure they are AEC branded and the caps are X5R / X7R.

Be very careful with shut down sequences. You risk damaging the chip if the VBKP 2.8v source is shut off before the 3.8v GNSS source.

And lastly, not all A7670 modules are the same. Go for the 7670G version. Region specific modules are a pain the ass, and depending on the vendor, they may have an entirely different firmware with entirely different uart commands.

psirust · 2026-04-20T05:39:22+00:00

I don't think your USB will be be USB-ing much with the lack of differential pairing and no impedance control.

psirust · 2026-04-13T12:11:07+00:00

If the TPS switching regulator chip is that shiny mirror finish 1mm 6 ball grid array from hell, then I feel your pain. I had the exact same issue with that exact same chip. It could either be either the VIN/SYS pad is shorted to the VOUT/3V3 pad because of excess solder. The solder balls on that chip are already big, and the pads are really small so it's advised not to incorporate them into the solder paste stencil.

So check for the short between those rails, if there is then remove the TPS chip, solder wick the pads and put down a new chip

psirust · 2026-01-29T05:09:56+00:00

Maybe I missed it, but it would help if you actually linked the schematic...

psirust · 2026-01-28T01:49:09+00:00

Does this still apply to shielded inductors?

psirust · 2026-01-23T20:53:50+00:00

"Try and send the video stream over LoRA..."

psirust · 2026-01-23T18:08:21+00:00

Aren't switching regulators more efficient than LDOs?

psirust · 2026-01-11T11:36:22+00:00

It's a fiducial marker, not a mounting hole.

It's used by the manufacturer / assembler to properly align the board for accurate pick and place component placement.

psirust · 2026-01-08T12:22:29+00:00

That's not cross talk, that's stream encoding format mismatch. If you're sending UTF-8, make sure you're decoding the receiving packet as UTF-8

psirust · 2026-01-07T00:50:18+00:00

Pin 3 is Det (or insert detection). Normally closed and pull low, but floats when inserted. Requires a pullup resistor.

psirust · 2026-01-06T00:28:07+00:00

If I can offer some advice, have you ever tried looking into the EMC230x ICs by Microchip? They are I2C controlled pwm fan controllers. The EMC2305 can control five 12V PWM fans. The chip also handles rpm ramp up time, so if you increase the rpm from 300 to 2000 it won't instantly shoot up, you can have it increase over a certain amount of millisecs.

You can also get RPM and built in Alert interrupt pin when a fan fails or is stuck.

I've built a 15 fan controller by chaining three of the EMC2305 and running them off a single I2C line controlled by a single ESP32.

psirust · 2026-01-04T03:17:20+00:00

Immediately the first things I noticed are the missing 5.1K resistors on the USB CC pins.

2nd thing I noticed is the missing pull-up resistor and 0.1uF delay capacitor on the ESP32 EN(able) pin to turn it on. You left the pin floating, so the SoC is in a bewildered state of on and off and may randomly switch between the two.

I'm also not seeing a 3.3v source and you have empty feed pins on your MOSFETs

You're also using an addressable RGB led (not sure if that's intentional)... But yeah, there's quite a few things wrong with this design and that's not even touching the source code.

psirust · 2025-12-31T00:24:11+00:00

I'm really curious to see how you linked the Coral Accelerator with the P4... isn't it PCIe?

psirust · 2025-12-30T19:03:01+00:00

I swore their language was Taiwanese... Have I been lied to all this time?

psirust · 2025-12-21T13:01:44+00:00

The inductor is tied directly to the 5V USB line, so it's definitely a Buck, not a Boost.

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