Avionics: Adding a lot more voice alerts on GRT EFISs!

GRT EFIS Audio Alerts

Update 15-Mar-23:  Added alarm #289.

Update 16-Apr-19:  Added alarm #288.


Executive summary: At least 80 undocumented audio alerts are available on most GRT EFISs. This post explains what they are and how to enable most of them.

Background

The GRT HXr, HX, Sport and Horizon EX, Sport SX, Mini-GA and (I think) Mini Series EFISs have an audio output to provide audio alerts to your intercom using audio files that you must provide.  The output is found on pin B24 with ground on B25 for all but the Minis.  GRT has disclosed only 17 special alerts which use predefined filenames (shown in parentheses below) which are typically copied on to the EFIS from a USB drive using the Set Menu on the EFIS:

• Minimum oil pressure (oil_pressure.wav)
• Minimum fuel pressure (fuel_pressure.wav)
• AoA tone near stall, repeats more frequently closer to stall (filename unknown)
• Obstacle alarm (obstacle.wav)
• New traffic within alert criteria (traffic.wav)
• Autopilot disconnect 
• Manual (ap_disconnect_advisory.wav)
• Automatic(ap_disconnect_warning.wav)
• Maximum oil temperature (oil_temperature)
• Maximum CHT (cht.wav)
• Low/High voltage (low_volts.wav and high_volts.wav)
• Maximum fuel flow (fuel_flow.wav)
• Vne exceeded (speed.wav)
• Trim alert from GRT pitch servo, repeats every 30 seconds (trim.wav)
• SAP height above runway at 500, 200, and 100 feet (500.wav, 200.wav,1500.wav)
• Minimums if decision altitude is set (minimums.wav)
• Approaching minimums when 200 feet above decision altitude (approaching_minimums.wav)
• Waypoint sequence (waypoint.wav)

However, I recently became aware of this post on GRT's forums which explains that "every unique alarm can have its own audio file using an internal alarm number".  The format that GRT uses for those files is alarm####.wav where #### is the four digit number of the alarm.  Unfortunately, GRT did not originally provide documentation of the alarm numbers since releasing the initial firmware update for audio support in 2015 and to date, still has not.   But, that information lead me to identifying nearly 60 undocumented alarms.

Below I...

1. Explain how the EFIS manages audio alerts.
2. Explain how to add the additional alerts.
3. Show the additional undocumented alerts I've identified thus far
4. Provide audio files for you to use.
5. Explain the process I used to determine the undocumented alarms.

GRT EFIS Alert Process

First, it's helpful to understand how the EFIS alert annunciation process works.

Short version:

1. Alarm occurs.
2. EFIS looks for associated file.
3. EFIS plays the file.

Long version:

1. Alarm occurs with unique internal four-digit alarm number..
2. EFIS looks for the associated alarm####.wav or predefined file in the Alerts folder first on the USB drive, then on the EFIS itself.  
3. If the file is found, it is played.  
• If there are duplicate files then the USB file is played first, immediately followed by the EFIS file resulting in a double alert. 
• This would occur with the predefined special alarms like obstacle.wav which is also alarm0091.wav.
• To avoid double alerts, don't provide both files.
• For example you may have already placed obstacle.wav on your EFIS, so don't provide alarm0091.wav also unless you want to hear both wav files:  "obstacle, obstacle".

How to Add Your Own Voiced Alerts

You can find the undocumented alarms in the table shown below in the section "Alarms I Have Identified".  Here are the steps to expand your voiced alarms on your EFIS:

1. Decide what message you want your EFIS to voice for each alarm you're interested in having.
2. Create the voices using an online text-to-voice service.  
• I use Amazon Polly which requires a (free) Amazon Web Services account.
• If you prefer, you can use the files that I made.  The link is found below in the Files You Can Use for Alerts section.
  
3. Save each message with the proper filename (alarm####.wav - must use four digits).
• Use a wav file in 16-bit, Microsoft PCM format with 44.1 kHz or 22.05 kHz sampling rate.  I have confirmed that those work, but other sampling rates and wav formats may also.  
• I suggest using the free Open Source program Audacity to manipulate wav files.
4. Copy your new alarm####.wav files onto your USB drive into a folder named Alerts.
5. Plug the USB drive into your EFIS. 
6. You're done.  Verify it works on the ground with engine off, prior to flight.
• I don't suggest copying the files to your EFIS since I'm not clear on how to delete them without wiping all settings on the EFIS.
7. Consider carrying the full set of alarm files to help identify additional alarms as explained in the "Files You Can Use for Alerts" section below.

Additional items to consider:

• If you decide to copy your alarm files to your EFIS, your collection of selected audio files should not exceed 100 MB in size as the EFIS will not copy more than that.
• Keep in mind that the EFIS will play the entire file when the alarm triggers, so very terse messages are probably best.
• For example, "hey, pilot in command, your cylinder head temperature on cylinder 2 is too high, do something about it!" is not a wise choice for alarm 76.  
• Not all alarms get a preceding tone (a "blip" or "whoop").  If you want your alarms to have a preceding tone, you may need to add the tone to the wav file you plan to use.
• My AUX inputs probably don't match yours.  Be sure to use messages that match your configuration.
• I make mistakes.

Alarms I Have Identified

If you find additional alarms or errors, contact me.  Thanks to user "R" for finding several additional alerts.

Columns:

• Alarm:  Alarm number (remember, the number in alarm####.wav needs to be four digits).
• Message:  My suggested voice message for the alarm.  You can use something different if you prefer.  
• Note:  Your AUX inputs are probably different than mine so you will need to change the associated messages to match your configuration.
• Description:  What the alarm represents.
• Predefined:  If it is also a predefined alarm, the associated special filename. 

Alarm	Message Used	Description	Predefined?
0	Avionics data, unavailable.	Serial and EthLink no data
2	Flight time limit	Flight time limit
3	Interval elapsed	Interval alarm
5	Oil pressure high.	Max Oil Pressure	oil_pressure.wav
6	Oil pressure, low.	Min Oil Pressure	oil_pressure.wav
8	Oil temperature high.	Max Oil Temp
9	Oil temperature, low.	Min Oil Temp
10	RPM high	RPM High
11	RPM low	RPM Low
12	Total fuel low.	Min Fuel
13	Manifold pressure high.	EIS1 Max AUX1
14	Left fuel tank high.	EIS1 Max AUX2
15	Right fuel tank high.	EIS1 Max AUX3
16	Alternator current high.	EIS1 Max AUX4
17	Battery current high.	EIS1 Max AUX5
18	Fuel pressure high.	EIS1 Max AUX6
19	Manifold pressure, low.	EIS1 Min AUX1
20	Left fuel tank, low.	EIS1 Min AUX2
21	Right fuel tank ,low.	EIS1 Min AUX3
22	Alternator current, low.	EIS1 Min AUX4
23	Battery current, low.	EIS1 Min AUX5
24	Fuel pressure, low.	EIS1 Min AUX6
25	Coolant temperature high	Max Coolant Temp
26	Coolant temperature low	Min Coolant Temp
27	EIS voltage high	Max EIS Voltage
28	EIS voltage low	Min EIS Voltage
29	EFIS bus one voltage high	Max EFIS Voltage Bus 1	high_volts.wav
30	EFIS bus one voltage low	Min EFIS Voltage Bus 1	low_volts.wav
31	EFIS bus two voltage high	Max EFIS Voltage Bus 2
32	EFIS bus two voltage low	Min EFIS Voltage Bus 2
33	EFIS bus three voltage high	Max EFIS Voltage Bus 3
34	EFIS bus three voltage low	Min EFIS Voltage Bus 3
35	Carburetor temperature	Carb temp between upper and lower limit
36	Exhaust 1 temperature high.	Max EGT1
37	Exhaust 2 temperature high.	Max EGT2
38	Exhaust 3 temperature high.	Max EGT3
39	Exhaust 4 temperature high.	Max EGT4
40	Exhaust 1 temperature, low.	Min EGT1
41	Exhaust 2 temperature, low.	Min EGT2
42	Exhaust 3 temperature, low.	Min EGT3
43	Exhaust 4 temperature, low.	Min EGT4
72	EGT span high	EGT Span Too Large
75	Cylinder 1 temperature high.	Max CHT1
76	Cylinder 2 temperature high.	Max CHT2
77	Cylinder 3 temperature high.	Max CHT3
78	Cylinder 4 temperature high.	Max CHT4
79	Cylinder 1 temperature, low.	Min CHT1
80	Cylinder 2 temperature, low.	Min CHT2
81	Cylinder 3 temperature, low.	Min CHT3
82	Cylinder 4 temperature, low.	Min CHT4
85	Cylinder 1 cooling fast	EIS1 CHT1 Cooling Too Fast
86	Cylinder 2 cooling fast	EIS1 CHT2 Cooling Too Fast
87	Cylinder 3 cooling fast	EIS1 CHT3 Cooling Too Fast
88	Cylinder 4 cooling fast	EIS1 CHT4 Cooling Too Fast
91	Obstacle	Obstacle	obstacle.wav
92	Altitude deviation	Check Altitude
93	Analog input 1 too high
94	Analog input 2 too high
95	Analog input 3 too high
96	Analog input 4 too high
97	Analog input 5 too high
98	Analog input 6 too high
99	Analog input 7 too high
100	Analog input 8 too high
101	Analog input 1 too low
102	Analog input 2 too low
103	Analog input 3 too low
104	Analog input 4 too low
105	Analog input 5 too low
106	Analog input 6 too low
107	Analog input 7 too low
108	Analog input 8 too low
121	CO guardian unit failure	CO Guardian Unit Failure
122	CO level unsafe	Carbon Monoxide Level Unsafe
123	Cabin pressure unsafe	Cabin Pressure Unsafe
124	Check bio data	Life Guardian periodic bio data check
288	Roll trim required	Roll trim required
289	Pitch trim required	Pitch trim required
302	RPM range limit	TachHi/Lo alarm

*Note:  "Traffic", "Speed", "Autopilot disconnect", G maximum limits and the "AoA" tone do not appear to have an associated alarm number.

Files You Can Use for Alerts

Here are the files with voiced alarms in an 8 MB zip file (let's call these the messaged alarms) and the files for the predefined alerts in a 1.1 MB zip file that I use, if you wish to use them too.

How You Can Help Identify Additional Alarms

I'm also giving this link which has the 10,000 alarm files that I assembled in a 318 MB 7z file that just voices the number of the associated alarm (let's call these the numbered alarms).  For example, alarm1293.wav simply says "one thousand two hundred and ninety three".  To decompress a 7z file you will need to use 7zip (for Windows) or Keka (for Mac).

Why do I provide those numbered alerts files?  If you use them, when your system triggers an alarm I haven't documented yet (e.g., I don't have three props, TIT sensor, etc., so I don't plan to find what their alarm numbers are), you'll hear the number and you can contact me with the information so I can add it to the list. 

To use these numbered alarms and still keep your messaged alarms:

1. Copy the 10,000 numbered alarms onto the USB drive's Alerts folder.
2. Copy the messaged alarm files.
• Overwrite the associated numbered alarms from Step 1 so you still get the messages you want instead of hearing numbers.
3. Delete any file with an associated alarm you're not interested in hearing.
• For example
• Maybe you don't want to hear when your RPM gets too low so delete alarm0011.wav.  
• You already copied obstacle.wav to your EFIS so you don't need alarm0091.wav.
4. Plug the USB drive into your EFIS. 
5. You're done.  If you find additional alarms, please contact me.
   

The Process I Used To Determine Alarm Numbers

Short version:

1. Created 10,000 wav files, each which voices the numbers 0-9,999.
2. Placed them in the Alerts folder on a USB drive connected to the EFIS.
3. Artificially caused as many alarms as I could.
4. Wrote down the number I heard for each alarm.
5. Noted duplicates (i.e., when predefined alarms were followed by a number too).
6. Created alarm files with the messages I want to hear.
7. Updated numbered alarm files with messaged alarm files.
8. Keep numbered alarm files on USB drive to facilitate identification of alerts in the future.

Long version: 

Armed with the file format, it was trivial to decode most of the alarms that were relevant to my installation and setup.  All I needed to do was create 10,000 audio files that announce numbers, then each alarm would annunciate as a number and I could simply write down what each corresponded to.

So, to save myself the time of manually creating one thousand wav files I downloaded pre-recorded number files (0-99, x00, x000).  These represented only 118 of the files I need.  I needed the remaining 9,882 audio files.  But with those 118 files, I could use ffmpeg and some simple basic DOS scripts that I quickly wrote to automatically create and assemble files "alarm0000.wav" through "alarm9999.wav" giving me the complete collection of 10,000 files, each of which annunciates the associated number.  I further used ffmpeg to ensure each had the file format Windows PCM, 44,100 Hz, mono, 16-bit (as that's what I used for the voice alerts defined above, so I knew that format would work) and was amplified 5 dB to make them louder without too much clipping.

Next, knowing that the EFIS will first look for audio files on the USB drive and then use the internal ones, I created an "Alerts" folder with those 10,000 alarm wav files on a USB drive and connected it to my EFIS.  I then sat in the plane in my hangar and forced as many alarms as I could (by adjusting the criteria in the various settings pages), and as I heard each number in my headset, I wrote down what alarm each corresponded to.  Next, I flew the aircraft and forced the remainder of the alerts.  Then I assembled what I learned in a spreadsheet.

Finally, I went home and decided which alarms I actually wanted voiced, typed out what I wanted for each then had them voiced by ivona.  I then took those voices, dumped them into separate wav files with the correct filenames, as determined by their associated alarm numbers, and placed them on the USB drive that stays with my EFIS (it also has the charts and approach plates).

Whilst I would have preferred GRT's documentation, they gave enough information for me to create it for myself.

Contact me.