109 lines
5.8 KiB
Markdown
109 lines
5.8 KiB
Markdown
# cat-tracker
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A multi-function application designed to run on a pi node. When used in a mesh network, this app will help track your cat with a CC2500 based radio collar, using complementary CC2500 based radio modules interfaced with your Pi.
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The implementation here uses CC2500 register values which intend to mimic my [Girafus M07A](https://www.girafus.com/en-en/collections/peilsender/products/ersatzteil-basismodul-fur-girafus%C2%AE-pro-track-tor-katzen-hunde-haustier-kleintier-sucher) unit. This unit is paired with my associated [tracker](https://www.girafus.com/en-en/collections/peilsender/products/extra-sender-tag-fur-den-girafus%C2%AE-pro-track-tor-haustier-hund-katze-kleintier-finder-sucher-ortung)
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## Links
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* [Arduion Forum Port](https://forum.arduino.cc/t/replicating-a-signal-from-a-locating-device-2-4ghz-to-locate-tag/321993/2)
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* [cc2500 data sheet](./cc2500.pdf)
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* [C Code transciever example](https://github.com/alexbirkett/cc2500-raspberry-pi)
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## CC2500 to Raspberry Pi GPIO Pin Mapping
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| CC2500 Pin | Function Description | Raspberry Pi GPIO Pin | GPIO Number |
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|------------|------------------------------------------------------|-------------------------------|-------------|
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| GND | Ground | Pin 6 | - |
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| VCC | 3.3V Power (⚠️ **Do not use 5V**) | Pin 1 or Pin 17 | - |
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### SPI Connections
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| CC2500 Pin | Function | Raspberry Pi GPIO Pin | GPIO Number |
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|------------|----------|-------------------------------|-------------|
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| SI | MOSI | Pin 19 | GPIO 10 |
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| SCK | SCLK | Pin 23 | GPIO 11 |
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| CSN | CE0 (Chip Select) | Pin 24 | GPIO 8 |
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| SO | MISO | Pin 21 | GPIO 9 |
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### Optional Pins
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| CC2500 Pin | Function | Raspberry Pi GPIO Pin | GPIO Number |
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|------------|-------------------------------------------|-------------------------------|-------------|
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| GDO0 | Interrupt/Data Ready | Pin 12 | GPIO 18 |
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| GDO2 | Additional Interrupt/Data Line | Pin 22 | GPIO 25 |
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### Power Amplifier Pins (If Applicable)
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| CC2500 Pin | Function | Raspberry Pi GPIO Pin | Notes |
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|------------|-------------------------------------------|-------------------------------|----------------------------------------|
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| PA_EN | Control Power Amplifier (Optional) | Any GPIO Pin | Connect if amplifier control is needed |
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| PA_EX | Reserved | Not Connected | Only connect if required |
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## Reverse Engineering the Registers
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### SmartRF Studio
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#### Install
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[SmartRF Studio](https://www.ti.com/tool/SMARTRFTM-STUDIO#downloads) will automatically generate a configuration for the CC2500 Radio based on some RF parameters
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* A free registration and login is required to download this app from Texas Instruments
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* The app seems to run well via `wine` on linux. I chose to install it on an actual Windows OS, then copy the binaries.
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#### Copy Register JSON template
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When this is installed, copy the code export json file to help export the initial register configuration in a JSON format
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```bash
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cp srfexp_json.xml "~/Documents/Texas Instruments/SmartRF Studio v7/codeexport/."
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# Example copy command for linux+wine
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```
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#### Understanding necessary RF Parameters
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In SmartRF Studio, open the CC2500 Device Controller under the 2.4 GHZ list.
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At the time of writing, it is believed this device uses 250 kBaud MSK encoding. We will choose this option.
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Next we need to figure out the Base Frequency, Channel numbers, and Channel Spacing
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### Singal Capture
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I have captured the initial signal emitted by the handheld unit when it is first powered on. To do this, I have used a HackRF SDR + gqrx application on linux.
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The known frequency range is 2400 – 2483.5 MHz, and my SDR has a 20 MHZ bandwidth. I choose sweep for signals by tuning the following frequencies
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| Sweep # | Center Frequency | Center Frequency (kHz) | Approx. Coverage (MHz) | Approx. Coverage (kHz) |
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|---------|------------------|-------------------------|-------------------------|-----------------------------|
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| 1 | 2410 MHz | 2,410,000 kHz | 2400 – 2420 MHz | 2,400,000 – 2,420,000 kHz |
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| 2 | 2430 MHz | 2,430,000 kHz | 2420 – 2440 MHz | 2,420,000 – 2,440,000 kHz |
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| 3 | 2450 MHz | 2,450,000 kHz | 2440 – 2460 MHz | 2,440,000 – 2,460,000 kHz |
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| 4 | 2470 MHz | 2,470,000 kHz | 2460 – 2480 MHz | 2,460,000 – 2,480,000 kHz |
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| 5 | 2483.5 MHz | 2,483,500 kHz | 2473.5 – 2483.5 MHz | 2,473,500 – 2,483,500 kHz |
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#### Signal 00
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2.423257000 GHz | 2423.257000 MHz | 2423257.000 kHz |
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#### Signal 0
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2.431258000 GHz | 2431.258000 MHz| 2431258.000 kHz
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#### Signal 1
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2.447257000 GHz | 2447.257000 MHz | 2447257.000 kHz
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#### Signal 2
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2.450225000 GHz | 2450.225000 MHz | 2450225.000 kHz
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#### Signal 3
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2.471275000 GHz | 2471.275000 MHz | 2471275.000 kHz
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#### Signal Summary
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* Base frequency: ? MHz
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* Date Rate ? Baud
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* Channel spacing: ? kHz
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* Signal channels:
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* Signal 00 → Channel ?
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* Signal 0 → Channel ?
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* Signal 1 → Channel ?
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* Signal 2 → Channel ?
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* Signal 3 → Channel ?
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## Run
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`python3 read.py` |