2024-11-25 04:39:31 +08:00
---
title: Chinese ZHONGKEWEI ATGM* GNSS modules comparison
author: peter
date: 2024-11-25 04:00:36 +0800
categories: [Electronics] # 0-2 categories. Blogging | Electronics | Programming | Mechanical | SelfHosting | Guides | University
tags: [gps,gnss,cheap,comparison,ublox] # 0-\infty. systems | embedded | rf | microwave | electronics | solidworks | automation | tip
# image: assets/img/2024-11-25-Chinese-ZHONGKEWEI-A/preview.png
---
The ZHONGKEWEI ATGM* series of GNSS modules appear to emulate the popular u-blox NEO and MAX series and are (almost) pin compatible.
| Model | GPS | BDS | GLONASS | Galileo | QZSS | VCC [V] | Interfaces | Internal SOC | TTFF [s] | Maximum output rate [Hz] | CEP50 [m] | Cost [AUD] |
| -------------------- | --- | --- | ------- | ------- | ---- | ------- | -------------------- | ------------ | -------- | ------------------------ | --------- | ---------- |
| ATGM332D-6N-74 | ✅ | ✅ | ✅ | ✅ | ✅ | 2.7-3.6 | UART,I2C,SPI | AT6668 | 23 | 10 | 1.5 | 5.3287 |
| ATGM336H-6N-74 | ✅ | ✅ | ✅ | ✅ | ✅ | 2.7-3.6 | UART,I2C,SPI | AT6668 | 23 | 10 | 1.5 | 5.3171 |
| ATGM336H-5N31 | ✅ | ✅ | ❌ | ❌ | ❌ | 2.7-3.6 | UART1,UART2 | AT6558 | 32 | 10 | 2.5 | 4.6255 |
| ATGM332D-5N31 | ✅ | ✅ | ❌ | ❌ | ❌ | 2.7-3.6 | UART1,UART2 | AT6558 | 32 | 10 | 2.5 | 4.1224 |
| ATGM332D-5NR32 | ✅ | ✅ | ❌ (?) | ❌ | ❌ | 1.8-3.6 | UART1,UART2 | AT6558R | 32 | 5 | 2.5 | 4.0525 |
| ATGM336H-5NR32 | ✅ | ✅ | ❌ (?) | ❌ | ❌ | 1.8-3.6 | UART1,UART2 | AT6558R | 32 | 5 | 2.5 | 3.8498 |
| ATGM332D-5N11 | ✅ | ❌ | ❌ | ❌ | ❌ | 2.7-3.6 | UART1,UART2 | AT6558 | 32 | 10 | 2.5 | 5.9460 |
| ATGM336H-5N11 | ✅ | ❌ | ❌ | ❌ | ❌ | 2.7-3.6 | UART1,UART2 | AT6558 | 32 | 10 | 2.5 | 5.0609 |
| NEO-M9N (**u-blox**) | ✅ | ✅ | ✅ | ✅ | ✅ | 2.7-3.6 | UART,I2C,SPI,**USB** | UBX-M9140-KB | 24 | **25** | 2.0 | 45 |
These parameters seem to be the same for all ATGM modules:
| Key | Value | Note |
| ---------------------------- | -------- | ------------------------ |
| Cold start sensitivity [dBm] | -148 | |
| Tracking sensitivity [dBm] | -162 | |
| Protocols | NMEA0183 | |
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| Assisted GNSS | ✅ | |
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| Battery and RTC | ✅ | |
| Lockout speed [m/s] | 515 | Not specified on AT6668? |
| Lockout altitude [m] | 18000 | Not specified on AT6668? |
| Lockout acceleration [g] | 4 | Not specified on AT6668? |
The main differences compared to the NEO-M9N are:
- Significantly lower cost
- Lower maximum output data rate of only 10 Hz
- Slightly higher lockout speed of 515 m/s
- Lower lockout altitude of 18000 m (compared to 80000 m)
- Lacks USB and lacks UBX or any binary output format
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## AGNSS
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 ).
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.
```py
addr = "121.41.40.95" # Server address
port = 2621 # port
message = b"user=freetrial;pwd=123456;cmd=full;lat=30;lon=120;" # Request message
import socket
socket.setdefaulttimeout(4)
client = socket.socket()
client.connect((addr, port))
client.send(message)
reply_data = b""
while True:
current_reply = client.recv(1024)
if len(current_reply) == 0:
break
else:
reply_data += current_reply
print(reply_data)
import serial
tty = serial.Serial()
tty.port = "COM1"
tty.baudrate = 9600
tty.open()
tty.write(reply_data)
tty.close()
```
The document seems to indicate the AGNSS service is supported by China Aerospace Science and Industry Corporation.
