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Xinyuan-LilyGO / T-SIM7600X

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NMEA-0183 register bit 11 - RESERVED ?? #103

Closed PsySc0rpi0n closed 1 month ago

PsySc0rpi0n commented 1 month ago

Hello.

I was digging through the configuration bits of NMEA-0183 messages in the SIM7600 datasheet. I believe that, probalbly this is not a question for the firmware developers, but probably they know about this and I would love confirmation (or not).

In the datasheet, the descritption for AT commands to configure the NMEA-0183 messages, says that bit 11 is RESERVED. However, the example given there in the datasheet, and also the one used in the firmware examples, the decimal number to setup the NMEA-0183 messages, which is 200191 (binary 110000110111111111) show us that bit 11 is set to 1. Is this supposed to be set to 1? All the other RESERVED bits are set to 0, at least in this 200191 number!

Datasheet here Page 375 and 376

Line of code using this setting: Line 96

PsySc0rpi0n commented 1 month ago

Apparently, the value 200191 is not correct. If we try to force this value, it will respond OK, however if you query the command with AT+CGPSNMEA? it will respond +CGPSNMEA: 198143 which is 200191 minus that bit 11 (counting from 0), meaning 200191 - 2048 = 198143.

I think we can conclude that the value 200191 is not accepted because that bit 11 will not be set due to being a RESERVED bit!