Add General Motors TPMS #3191

e100 · 2025-02-08T02:25:02Z

This adds a decoder for one of the protocols discussed in #3123

zuckschwerdt · 2025-02-08T11:39:33Z

src/devices/tpms_gm.c

@@ -0,0 +1,161 @@
+/** @file
+    General Motors Aftermarket TPMS


End the first line with a dot.

zuckschwerdt · 2025-02-08T11:39:51Z

src/devices/tpms_gm.c

+*/
+
+#include "decoder.h"
+#include "r_util.h"


include only decoder.h if possible.

zuckschwerdt · 2025-02-08T11:40:07Z

src/devices/tpms_gm.c

+#include <stdio.h>
+#include <inttypes.h>  // Needed for PRIX64
+
+static uint8_t const preamble_pattern[6] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00};


move this into the decoder function.

zuckschwerdt · 2025-02-08T11:40:21Z

src/devices/tpms_gm.c

+static uint8_t const preamble_pattern[6] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
+
+/**
+Data was detected an initially captured using:


first line should be the same as line 2

zuckschwerdt · 2025-02-08T11:40:35Z

src/devices/tpms_gm.c

+/**
+Data was detected an initially captured using:
+
+  rtl_433 -X 'n=name,m=OOK_MC_ZEROBIT,s=120,l=0,r=15600'


four spaces indent for code lines

zuckschwerdt · 2025-02-08T11:40:42Z

src/devices/tpms_gm.c

+
+
+
+130 bits


zuckschwerdt · 2025-02-08T11:40:57Z

src/devices/tpms_gm.c

+130 bits
+AAAAAAAAAAAASSSSDDDDIIIIIIPPTTCCX
+0000000000004c90007849176600536d0
+ Data layout:


no indent for header lines

zuckschwerdt · 2025-02-08T11:41:10Z

src/devices/tpms_gm.c

+Bit 5 of status indicates low battery when set to 1
+Bits 0,1,8 are set to 0 to indicate learn mode and 1 for operational mode.
+The sensors drop to learn mode when detecting a large pressure drop
+or when activated with the learning tool


end sentences with a dot

zuckschwerdt · 2025-02-08T11:41:51Z

src/devices/tpms_gm.c

+    // But I think it might be best to allow the user to
+    // to add their own offset when consuming the data
+    float pressure_kpa = (pressure_raw * 2.75);
+    float pressure_psi = kpa2psi(pressure_kpa);


output native units, don't convert in decoders

zuckschwerdt · 2025-02-08T11:42:21Z

src/devices/tpms_gm.c

+    int bit0 = (status >> 0) & 1;
+
+    // Status bits
+    int learn_mode = ((bit8 == 0) && (bit1 == 0) && (bit0 == 0)) ? 1 : 0;


don't ? 1 : 0 on a bool

zuckschwerdt · 2025-02-08T11:43:15Z

Thanks! Some code style comments :)

e100 · 2025-02-08T14:21:20Z

@zuckschwerdt The docs suggest id should be integer but I noticed that all of the TPMS decoders output a hex string for id, should I change my code to be consistent with other TPMS?

…coders

zuckschwerdt · 2025-02-08T14:54:54Z

A plain int for "id" is preferred. You can use something like "id", "", DATA_FORMAT, "%08x", DATA_INT, id, if you want the hex display in the console to easier match with an id printed on the sensors.

e100 · 2025-02-08T15:46:41Z

I believe all of your suggestions have been addressed.

zuckschwerdt · 2025-02-10T09:43:39Z

Thanks!
For the decoder doc-comment, indent only code blocks, and those by four spaces. E.g. this

/**
    General Motors Aftermarket TPMS.
Data was detected and initially captured using:
    rtl_433 -X 'n=name,m=OOK_MC_ZEROBIT,s=120,l=0,r=15600'
    130 bits
AAAAAAAAAAAAFFFFDDDDIIIIIIPPTTCCX
0000000000004c90007849176600536d0
Data layout:
   AAAAAAAAAAAAFFFFDDDDIIIIIIPPTTCCX

should be


/**
General Motors Aftermarket TPMS.

Data was detected and initially captured using:
    rtl_433 -X 'n=name,m=OOK_MC_ZEROBIT,s=120,l=0,r=15600'

130 bits:
    AAAAAAAAAAAAFFFFDDDDIIIIIIPPTTCCX
    0000000000004c90007849176600536d0

Data layout:
    AAAAAAAAAAAAFFFFDDDDIIIIIIPPTTCCX

computed_checksum % 256 is usually written computed_checksum & 0xff.

flags, pressure_raw, temperature_raw should just be int.

The model must follow https://triq.org/rtl_433/DATA_FORMAT.html, likely GM-Aftermarket.

Run ./maintainer_update.py to get the readme changes.

e100 · 2025-02-10T21:49:14Z

@zuckschwerdt
Thanks for the guidance and patience.

Hopefully I have not overlooked anything this time.
I've also sent a pull request to the test repo with some recordings and json

e100 added 3 commits February 5, 2025 22:26

Added decoder for GM 130bit protocol

4611155

Updated model and added documentation

493f9b2

Removed pressure offset and raw output

aaa43a0

zuckschwerdt reviewed Feb 8, 2025

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src/devices/tpms_gm.c Outdated

@@ -0,0 +1,161 @@

/** @file

General Motors Aftermarket TPMS

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End the first line with a dot.

zuckschwerdt reviewed Feb 8, 2025

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src/devices/tpms_gm.c Outdated

*/

#include "decoder.h"

#include "r_util.h"

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include only decoder.h if possible.

zuckschwerdt reviewed Feb 8, 2025

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src/devices/tpms_gm.c Outdated

130 bits

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indent

zuckschwerdt reviewed Feb 8, 2025

View reviewed changes

Formatting and changed status to flags to be consistent with other de…

f9ac647

…coders

Fixed typo and removed unneded conditional

9bbc7e4

e100 added 2 commits February 10, 2025 16:06

Updated fix checksum, datatype, formatting and model

3e3678c

Updated readme and example config

2a16a4f

zuckschwerdt merged commit 474feb5 into merbanan:master Feb 13, 2025
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Add General Motors TPMS #3191

Add General Motors TPMS #3191

e100 commented Feb 8, 2025

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Add General Motors TPMS #3191

Add General Motors TPMS #3191

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e100 commented Feb 8, 2025

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zuckschwerdt commented Feb 8, 2025

e100 commented Feb 8, 2025

zuckschwerdt commented Feb 8, 2025

e100 commented Feb 8, 2025

zuckschwerdt commented Feb 10, 2025

e100 commented Feb 10, 2025 • edited Loading

e100 commented Feb 10, 2025 •

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