USFlyer wrote:
AHRS/ADHRS are embedded devices part electronics (discrete device chips) and part mechanical (gyros etc). They do not have a general CPU, RAM, disk. The firmware is chip based and not updated by anyone except the manufacturer. That would require removal of the device and shipment back to the factory…
Sure it is an embedded device with a microprocessor which contains it’s memory internally. This microchip firmware is updated by avionics shops (and offcourse supplied by manufacturer). 100% sure that updating is done on these. That it doesn’t have external RAM or disk, doesn’t mean it doesn’t get updated.
It does not get updated by the end customer in these cases.
NIL: Here’s a video I made in a Cessna 182T w G1000 a couple years ago .
When I first posted this on another forum I got a call from Garmin asking if they could “help” 
ps: luckily, we were VFR at the time ..
I had the same rapid rotation of the GPS track (but not the compass i.e. the fluxgate + the DG) in 2004, on the flight from Wangen Lachen LSPV to Corfu LGKR. We were at about 1000ft, going down the middle of the Adriatic because the Italian controller told me to get out of his airspace after the one before him cleared me through it I had two GPS receivers and both did the same.
From the writeup:
I wonder whether that G1000 HSI in the video was based on the GPS track? What was the outcome of any investigation?
Peter wrote:
I wonder whether that G1000 HSI in the video was based on the GPS track?
Normally the HSI is magnetic. There should be a magenta diamond at the circumference of the HSI “card” showing GPS track, but I can’t find it in the video…
Peter wrote:
What was the outcome of any investigation?
All I know is the plane was dropped off at Troyes Aviation and that was the last I heard of it.
The HSI is normally magnetic, sure, but on some systems you get an “auto switch” on the map, if the map is set to “track up”, in that when stationary on the ground you get an orientation based on the compass heading, and when you start moving, and it gets a GPS track computed, it switches to the GPS track. This might be a possible mechanism for this kind of failure, especially if more than one thing packs up.
What does the map orientation have to do with HSI?
Tablet type “pseudo HSI” are often track based, due to lack of magnetometer or lack of tie down to the airframe, but I’ve never seen this in certified avionics, I’d be surprised you could get something like that approved. And I’ve not seen a HSI you could set to north up 
USFlyer wrote:
AHRS/ADHRS are embedded devices part electronics (discrete device chips) and part mechanical (gyros etc). They do not have a general CPU, RAM, disk. The firmware is chip based and not updated by anyone except the manufacturer. That would require removal of the device and shipment back to the factory…
I think you’re splitting hairs. You’ll probably find that most of these DO have a general purpose CPU, RAM and flash – but it’s all integrated into a single chip (the microcontroller) rather having an external CPU bus. But that ARM M0 core inside your AHRS is most certainly a general purpose CPU core. The real difference is the CPU bus never leaves the microcontroller die, but it’s still very much there, and still has RAM, flash ROM and peripherals attached to it.
Most things these days that involve “intelligence” have a processor, which is typically a PIC, Atmel AT-something, ARM (rapidly taking over the embedded scene AFAICT), and some extended temp range applications use the old 8051 cores.
The data and address buses don’t leave the package and there is no hard disk, but it’s all definitely “software”.
The susceptibility to bugs, and vulnerabilities to “not previously seen” external data, is still there.
The main positive factor is that the software probably doesn’t get changed for years, and there is little or no external data going into the code. For example my Sandel SG102 AHRS 100.000% definitely contains a processor (it has RS232 and ARINC429 serial comms to the aircraft, and interfaces to the MT102 fluxgate via RS422) but there is no serial (digital) data going into it, except when running the RS232 laptop config. The data going out of it, both analog and digital serial, is obviously OK. So if it worked for a bit, it should continue. But…
Search here for “1/2012” and read on…
Software is ‘soft’ that means it can be easily and readily changed and may be more prone to ‘bugs’ because the changes are done more often. Firmware is NOT software. It is embedded code in a EPROM or PROM and is not committed to that state unless it is well debugged. To change firmware one must either replace the PROM, or reload the EPROM using special hardware. Microcode is even more static…it resides unchangeable in the design of the chip like a UART or a device controller (similar to what AHRS and ADHRS uses).
Software is found in general CPU machines with rotating or solid state disk and RAM.
There is no evidence that glass panel systems are ‘buggy’ and dangerous to use due to software issues. The code base for an avionics panel is well tried and tested. They have been around for decades now. New features are constantly being added by Dynon and Garmin and those may experience some issues, but those problems will not affect the basic six-pack of instrumentation on the panel.
