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81 lines
4.9 KiB
Markdown
81 lines
4.9 KiB
Markdown
---
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title: Chinese ZHONGKEWEI ATGM* GNSS modules comparison
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author: peter
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date: 2024-11-25 04:00:36 +0800
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categories: [Electronics] # 0-2 categories. Blogging | Electronics | Programming | Mechanical | SelfHosting | Guides | University
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tags: [gps,gnss,cheap,comparison,ublox] # 0-\infty. systems | embedded | rf | microwave | electronics | solidworks | automation | tip
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# image: assets/img/2024-11-25-Chinese-ZHONGKEWEI-A/preview.png
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---
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The ZHONGKEWEI ATGM* series of GNSS modules appear to emulate the popular u-blox NEO and MAX series and are (almost) pin compatible.
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| Model | GPS | BDS | GLONASS | Galileo | QZSS | VCC [V] | Interfaces | Internal SOC | TTFF [s] | Maximum output rate [Hz] | CEP50 [m] | Cost [AUD] |
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| -------------------- | --- | --- | ------- | ------- | ---- | ------- | -------------------- | ------------ | -------- | ------------------------ | --------- | ---------- |
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| ATGM332D-6N-74 | ✅ | ✅ | ✅ | ✅ | ✅ | 2.7-3.6 | UART,I2C,SPI | AT6668 | 23 | 10 | 1.5 | 5.3287 |
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| ATGM336H-6N-74 | ✅ | ✅ | ✅ | ✅ | ✅ | 2.7-3.6 | UART,I2C,SPI | AT6668 | 23 | 10 | 1.5 | 5.3171 |
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| ATGM336H-5N31 | ✅ | ✅ | ❌ | ❌ | ❌ | 2.7-3.6 | UART1,UART2 | AT6558 | 32 | 10 | 2.5 | 4.6255 |
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| ATGM332D-5N31 | ✅ | ✅ | ❌ | ❌ | ❌ | 2.7-3.6 | UART1,UART2 | AT6558 | 32 | 10 | 2.5 | 4.1224 |
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| ATGM332D-5NR32 | ✅ | ✅ | ❌ (?) | ❌ | ❌ | 1.8-3.6 | UART1,UART2 | AT6558R | 32 | 5 | 2.5 | 4.0525 |
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| ATGM336H-5NR32 | ✅ | ✅ | ❌ (?) | ❌ | ❌ | 1.8-3.6 | UART1,UART2 | AT6558R | 32 | 5 | 2.5 | 3.8498 |
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| ATGM332D-5N11 | ✅ | ❌ | ❌ | ❌ | ❌ | 2.7-3.6 | UART1,UART2 | AT6558 | 32 | 10 | 2.5 | 5.9460 |
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| ATGM336H-5N11 | ✅ | ❌ | ❌ | ❌ | ❌ | 2.7-3.6 | UART1,UART2 | AT6558 | 32 | 10 | 2.5 | 5.0609 |
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| NEO-M9N (**u-blox**) | ✅ | ✅ | ✅ | ✅ | ✅ | 2.7-3.6 | UART,I2C,SPI,**USB** | UBX-M9140-KB | 24 | **25** | 2.0 | 45 |
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These parameters seem to be the same for all ATGM modules:
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| Key | Value | Note |
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| ---------------------------- | -------- | ------------------------ |
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| Cold start sensitivity [dBm] | -148 | |
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| Tracking sensitivity [dBm] | -162 | |
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| Protocols | NMEA0183 | |
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| Assisted GNSS | ✅ | |
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| Battery and RTC | ✅ | |
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| Lockout speed [m/s] | 515 | Not specified on AT6668? |
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| Lockout altitude [m] | 18000 | Not specified on AT6668? |
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| Lockout acceleration [g] | 4 | Not specified on AT6668? |
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The main differences compared to the NEO-M9N are:
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- Significantly lower cost
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- Lower maximum output data rate of only 10 Hz
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- Slightly higher lockout speed of 515 m/s
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- Lower lockout altitude of 18000 m (compared to 80000 m)
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- Lacks USB and lacks UBX or any binary output format
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## AGNSS
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The GNSS receivers support assisted GNSS. The datasheet refers to another file, "AGNSS solution of ZhongKe micro". I could only find these slides from an [unofficial source](https://espruino.microcosm.app/api/v1/files/b589417f21931e2a2182c6785b846ac64ef64b40.pdf).
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The document contains the following code and the password and username of a free trial account which is rate-limited to 1000 requests per hour. The code works and the server is still online and will complain if you don't provide a username/password. I could not confirm that this account worked, either due to bots hitting the 1000 requests per hour rate limit or due to it being deactivated since the document was made.
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```py
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addr = "121.41.40.95" # Server address
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port = 2621 # port
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message = b"user=freetrial;pwd=123456;cmd=full;lat=30;lon=120;" # Request message
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import socket
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socket.setdefaulttimeout(4)
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client = socket.socket()
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client.connect((addr, port))
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client.send(message)
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reply_data = b""
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while True:
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current_reply = client.recv(1024)
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if len(current_reply) == 0:
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break
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else:
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reply_data += current_reply
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print(reply_data)
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import serial
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tty = serial.Serial()
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tty.port = "COM1"
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tty.baudrate = 9600
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tty.open()
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tty.write(reply_data)
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tty.close()
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```
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The document seems to indicate the AGNSS service is supported by China Aerospace Science and Industry Corporation.
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