76 4G模组境外拨号入网注意

1 引言

最近朋友把国内的设备拿到新加坡了，然后发现原本国内可以使用的设备无法在异国他乡联网，所以就叫我来看看，发现是附网返回状态、入网APN发生了改变导致的。另外，如果在境外使用国产4G模组拨号入网，也需要关注4G模组与本地基站是否能匹配上，如是否支持cat1以及当地基站是否支持模组支持的band（通过硬件手册可以查看到，如下图示）。

2 AT拨号实验

（1）在新加坡使用中国移动卡，AT拨号log如下：

[ Debug]: 1970-01-01 08:04:42, ML302_IO_Send:93: requests :: AT
[ Debug]: 1970-01-01 08:04:43, ML302_AsycnProcess:1501: >RCV:10:AT
OK[ Debug]: 1970-01-01 08:04:43, ML302_IO_Send:93: requests :: ATE0[ Debug]: 1970-01-01 08:04:43, ML302_AsycnProcess:1501: >RCV:12:ATE0
OK[  Info]: 1970-01-01 08:04:43, ML302_IsExist:618: find ml302 device
[ Debug]: 1970-01-01 08:04:46, ML302_IO_Send:93: requests :: AT+CGATT=0 //取消附着网络[ Debug]: 1970-01-01 08:04:47, ML302_AsycnProcess:1501: >RCV:6:
OK[ Debug]: 1970-01-01 08:04:47, ML302_IO_Send:93: requests :: AT+CGDCONT=1,"IP","cmnet" //设置apn[ Debug]: 1970-01-01 08:04:47, ML302_AsycnProcess:1501: >RCV:6:
OK[ Debug]: 1970-01-01 08:04:47, ML302_IO_Send:93: requests :: AT+CGATT=1 //附着网络[ Debug]: 1970-01-01 08:04:53, ML302_AsycnProcess:1501: >RCV:6:
OK[ Debug]: 1970-01-01 08:04:53, ML302_IO_Send:93: requests :: AT+CEREG? //查询网络注册状态[ Debug]: 1970-01-01 08:04:54, ML302_AsycnProcess:1501: >RCV:21:
+CEREG: 0,5 //注册成功5表示漫游
OK[ Debug]: 1970-01-01 08:04:54, ML302_IO_Send:93: requests :: AT+CEREG?[ Debug]: 1970-01-01 08:04:55, ML302_AsycnProcess:1501: >RCV:21:
+CEREG: 0,5
OK

上述发现，查看网络注册状态时，返回的是漫游状态，与境内的不一致。

所以，代码在判断返回值时需要注意。

（2）使用新加坡本地电信卡，AT拨号时需要注意

如果使用AT+CGDCONT=1,"IP","e-ideas" （电信的一个APN接入点），遇到了拨号不成功，

[ Debug]: 2024-07-06 15:42:05, ML302_IO_Send:93: requests :: AT
[ Debug]: 2024-07-06 15:42:06, ML302_AsycnProcess:1501: >RCV:10:AT
OK[ Debug]: 2024-07-06 15:42:06, ML302_IO_Send:93: requests :: ATE0[ Debug]: 2024-07-06 15:42:06, ML302_AsycnProcess:1501: >RCV:12:ATE0
OK[  Info]: 2024-07-06 15:42:06, ML302_IsExist:618: find ml302 device
[ Debug]: 2024-07-06 15:42:09, ML302_IO_Send:93: requests :: AT+CGATT=0[ Debug]: 2024-07-06 15:42:10, ML302_AsycnProcess:1501: >RCV:6:
OK[ Debug]: 2024-07-06 15:42:10, ML302_IO_Send:93: requests :: AT+CGDCONT=1,"IP","e-ideas" //怀疑是apn名字有-，导致模组设置失败[ Debug]: 2024-07-06 15:42:10, ML302_AsycnProcess:1501: >RCV:6:
OK[ Debug]: 2024-07-06 15:42:10, ML302_IO_Send:93: requests :: AT+CGATT=1[ Debug]: 2024-07-06 15:42:16, ML302_AsycnProcess:1501: >RCV:6:
OK[ Debug]: 2024-07-06 15:42:16, ML302_IO_Send:93: requests :: AT+CEREG?[ Debug]: 2024-07-06 15:42:17, ML302_AsycnProcess:1501: >RCV:21:
+CEREG: 0,1
OK[ Debug]: 2024-07-06 15:42:17, ML302_IO_Send:93: requests :: AT+CGACT=1,1[ Debug]: 2024-07-06 15:42:18, ML302_AsycnProcess:1501: >RCV:17:
+CME ERROR: 3 //返回OPERATION_NOT_ALLOWED错误[ Debug]: 2024-07-06 15:42:18, ML302_IO_Send:93: requests :: AT+CGACT=1,1[ Debug]: 2024-07-06 15:42:19, ML302_AsycnProcess:1501: >RCV:17:
+CME ERROR: 3 //返回OPERATION_NOT_ALLOWED错误

此时，更换另外一个电信的APN接入点，AT+CGDCONT=1,"IP","hicard" （电信另一个APN接入点）就可以了。