Pi OS 64-bit Ultimate GPS Hat no serial output

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jarrad_s
 
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Joined: Sat Apr 01, 2023 9:51 pm

Pi OS 64-bit Ultimate GPS Hat no serial output

Post by jarrad_s »

Hi all,

I had a RasPi 4 4Gb running 32-bit Pi OS (Bullseye) with the Ultimate GPS HAT and all was working fine. I decided I wanted to move to 64-bit for some container stuff that only worked on aarch64 and given the 64-bit version of Pi OS had been out for a while and it was working fine on another RasPi 4 4Gb I figured why not.

Unfortunately the HAT hasn't worked since the shift to 64-bit. I've replicated all the things from the 32-bit and even gone so far as to take one of my spare Pi's, wipe the OS and start fresh again with 64-bit to get it to work and zilch.

As it stands now, I have a Pi 4 4Gb running 64-bit Pi OS and I've done the following config:
Used raspi-config to disable serial console and enable serial port
Install screen and minicom
sudo systemctl disable hciuart
Edited /boot/config.txt to add dtoverlay=disable-bt

When I try to run sudo screen /dev/serial0 with the HAT attached, I get no data but the HAT LED shows it has a good fix (flashes red every 10 seconds).

When I do a loopback test on pins 8/10 GPIO 14/15, and I type something in, the data doesn't echo but I can see my key strokes.

Other things I have tried:
Edited /boot/config.txt to add nohz=off
Edited /boot/config.txt to add force_turbo=1
Edited /boot/config.txt to add dtoverlay=miniuart-bt
Edited /boot/config.txt to set minimum CPU frequencies
set CPU Governor to Performance
Tried using ttyAMA0 instead of serial0

None of the above works across 2 Pis. I'm leaning towards my HAT is fried.

I'm also not the best at soldering, but prior to the 32 to 64-bit cutover it was fine. I have re-soldered the pins to make sure that there is adequate connections. I am not the best at soldering at all, but I'm attaching a photo just in case.
IMG_7369.jpg
IMG_7369.jpg (856.05 KiB) Viewed 138 times
Am I right? Is the HAT faulty?

Thanks all

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adafruit_support_mike
 
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Joined: Thu Feb 11, 2010 2:51 pm

Re: Pi OS 64-bit Ultimate GPS Hat no serial output

Post by adafruit_support_mike »

The solder joints shown above could use some work. I see a lot of exposed gold on the pads, which often means the solder hasn't wetted the pads properly.

Take a look at our soldering tutorial:

https://learn.adafruit.com/adafruit-gui ... -soldering

Then give each joint a dab of flux and reheat it. You want a smooth, shiny cone that covers the pad and sweeps smoothly up to the pin.

From the photo, it looks like the solder stayed hot too long. Molten solder oxidizes in contact with air, and the oxide breaks into a powder that can mix into the molten metal. The oxide powder makes the solder pasty and incapable of flowing properly.

Flux improves things in two ways:

First, flux contains acids.. usually organic acids that are mostly neutral at room temperature, but become aggressive at soldering temperatures. The acid dissolves the oxide and purifies the molten metal.

Second, the flux floats on top of the molten solder, making a barrier that keeps air away from the molten metal and prevents new oxide from forming.

The surface tension of well-fluxed molten solder is very low, and gets lower as the solder gets hotter. That produces the effect of solder 'following' the heat.. the metal's natural tendency to flow improves as it gets closer to the tip of your iron.

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jarrad_s
 
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Joined: Sat Apr 01, 2023 9:51 pm

Re: Pi OS 64-bit Ultimate GPS Hat no serial output

Post by jarrad_s »

Thanks Mike,

Embarassingly, this was it. I got some flux, tidied up my soldering, and it worked straight away.

I'm not sure why that is seeing as it was working prior to the SD card swap, but at least the soldering is a lot better than it was.

Cheers!

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adafruit_support_mike
 
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Joined: Thu Feb 11, 2010 2:51 pm

Re: Pi OS 64-bit Ultimate GPS Hat no serial output

Post by adafruit_support_mike »

Glad to hear you got it working. Happy hacking!

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jbouse
 
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Joined: Sat Aug 20, 2016 10:26 pm

Re: Pi OS 64-bit Ultimate GPS Hat no serial output

Post by jbouse »

I'm also experiencing an issue with my Ultimate GPS HAT on a RPi 4B 4GB. I have two of the Ultimate GPS HATs with the PA6H GPS module. One, I soldered the header the other, I used the hammer solder-less header; both of them work fine in my RPi 2B without a problem but on the 4B, all I seem to get working is the PPS0. Still, the GPS serial doesn't provide any data despite the LED blinking like it has gotten a fix. I've tried both boards in the 2B and 4B with the exact GPS antenna, and everything works except when on the 4B.

Is this a 32- vs 64-bit issue or something specific with the 4B vs a 2/3B board? I'd like to get this working on the 4B instead of my 2B so I can have the WiFi support on board for the project I'm trying to use this for.

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adafruit_support_mike
 
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Re: Pi OS 64-bit Ultimate GPS Hat no serial output

Post by adafruit_support_mike »

Have you reconfigured the RasPi so its GPIO Serial port works?

The RasPi's microprocessor only has one real UART, and every version of the RasPi with built-in Wifi connects that UART to the BLE radio in the default configuration.

The microprocessor also has a software-based UART that derives its baudrate from the CPU clock. That's the one connected to the GPIO Serial pins on a RasPi with Wifi.

That would be fine except for one thing: Raspbian uses automatic clock throttling. When the CPU is idle, the OS slows the CPU clock down to save power. Then when the CPU is busy, the OS speeds the CPU clock up to keep the system responsive. Every time one of those changes happen, the baudrate of the software UART changes.

Putting all those pieces together, the GPIO Serial port is useless on RasPis with built-in Wifi.. at least with the default system configuration.

You can reconfigure the system so the GPIO Serial port works, but you have to give up something: either swapping the UARTs so GPIO Serial works but the BLE radio doesn't, or disabling automatic clock throttling so the software UART's baudrate never changes.

The RasPi Foundation has a page of documentation that explains the issue and the different ways to configure the system:

https://www.raspberrypi.com/documentati ... ring-uarts

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