SIM800C Development Board GSM GPRS Module Support Message bluetooth TTS DTMF Quad-band

Schematic:http://myosuploads3.hobbyant.com/products/20181127/20181127000501SIM800CV2.pdf
Overview
SIM800C is a quad-band GSM / GPRS module, its performance very stable, with small appearance and high cost-performance, to meet the various needs of customers. The operating frequency of SIM800C is GSM / GPRS 850/900/1800 / 1900MHz, can be used worldwide, you can achieve low power consumption of voice, SMS and data transmission, can be applied to a variety of design requirements of compact product.
Features
1. Input voltage range 5V-18V DC;
2. Self-propelled SIM card slot design, support 2G / 3G / 4G card or small card;
3. Module will connected to the network automatically after you power on it;
4. Compatible with a variety of single-chip serial port;
5. Reserved headset and microphone interface;
6. Support TTS DTMF function;
7. bluetooth 3.0 protocol, enhanced bluetooth antenna, support for serial port SPP and audio services;
8. Reserved lithium battery-powered BAT interface, you can use 3.7V lithium battery or 18650 lithium battery;
9. Reserved IPEX interface, SMA interface, spring antenna interface, can be used on different occasions;
10. With work indicator:the LED will flash 1 time per second when no network, no SIM card or SIM card inserted, and will flash 1 time per 3 seconds under normal conditions.
11. Board size:40.9*51.3mm
Interface description
GND:Power ground
VCC_IN:Power supply pin, input DC5V-20V
RI:Ring indicator
DTR:Data terminal preparation
TXD:TTL serial port transmission
RXD:TTL serial port receive
U2_R:module serial port 2 receive
U2_T:module serial port 2 send transmission
V_M:connect to the core voltage (5V/3.3V,it depend on your MCU) of MCU for level match(generally, NC also be OK for this pin)
ADC:ADC detection
SPP:Audio output positive
SPN:Audio output negative
MC-:Audio input negative
MC +:Audio input positive
PWR:Power enable or disable(enable when low level)
BAT:lithium battery input pin, 3.3v-4.4v
Basically instructions
The SIM800C mainly controlled by AT commands, so just find a USB convert to TTL serial port module,and 5V,GND,TXD,RXD pins connect to VCC_IN, GND,RXD, TXD pins of SIM800C
When the module is started, the indicator LED flashes once every 1 seconds, and after a period of time, the indicator LED flashes once every 3 seconds, it means the SIM800C start works normally.
Package included
1 x SIM800C Development Board
1 x Antenna
2 x normal pin