This is a 2G and industrial wireless communication module, integrated an GSM/GPRS module M6315, released by China Mobile,
supported GPRS class12 and GPRS CS-1, CS-2, CS-3, CS-4 encode, M6315 has LCC package type, features tiny dimension, highly reliability, strong anti-interference capability.
It can apply to the communication requirement on diversity industrial, electricity, petroleum, transportation, financial, etc
In the GSM module scheme, we added more hardware resources, 1 reserved speaker- SPK1, 1 onboard speaker-SPK2, LEDs, 2 alternative antenna.
M6315 is 2.8V power input, so in the hardware of GSM module, we added a Bidirectional Voltage-Level Translator (TXS0104E), to switch the power supply to 2.8V.
The Global System for Mobile Communications (GSM) is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe the protocols for second-generation (2G) digital cellular networks used by mobile devices such as mobile phones and tablets.
M5Stack Fire has occupied GPIO16 / 17 to connect with the PSRAM by default, it's conflict with TXD / RXD (GPIO16, GPIO17) of GSM module. Therefore, when using the GSM module with the M5Stack Fire, you might have to cut the TXD and RXD from GSM module and wire fly to another set of UART pin
M5Stack GSM Module (M6315)