The new GSM modem Falcom A2 is now available! Because of its small dimensions, it represents a practical alternative when traditional phone line is not available for connection between mobile PCs, GPS receivers or any device to connect them.
Some GSM modems on the market, we find the Falcom A1 Funkanlagen in which, through its serial communication port RS232-C, allows the connection with all devices supporting the same standard.
If this modem is GSM, in its category among more per formant market, it is certainly not the cheapest! Indeed, the only modem, without its connectivity, is about 3500 F HT. This parameter can not be neglected when it comes to design achievements for use semi-professional or even amateur, limits its use to industrial applications virtually. This justifies the birth of a baby brother, still manufactured by the same manufacturer and, if you have not already guessed, is called ... Falcom A2! The price of the youngest is about 2500 F, which is still a bit more affordable.
A2 is a simplified version of its predecessor and comes in a traditional metal enclosure. He has neither taken for voice, or DB-9 serial port.
The number of available functions is slightly lower than those of A.
The purpose of this paper is to make the Falcom A2 release that he is missing and to add all the elements necessary for it to be easily used by everyone! A
everyone now to imagine how they could use this assembly in accordance with their needs.
modem and connectors
The structure of our GSM modem gives an impression of robustness and simplicity of implementation. The case, tinned iron, is very compact (thickness 10.5 mm, width 50.5 mm, length 72 mm). The Falcom A2 is provided with a slot for inserting a standard SIM card, similar to that used in mobile phones, as well as 4 connectors, two high density, and an antenna connector (CN5).
CN1 connector, 40 pin (AMP), manages all the functions necessary for serial communication (RTS, CTS, DSR, etc.).. It also manages the circuit on / standby, the output for the speaker, the microphone input and a possible connection to external keyboard matrix of 5 rows of 4 columns.
connector CN2 to 15 pin, is dedicated to the communication port RS232-C. It manages the transmission of signals to CN1. Note that the transmission signals (TXD) and receive (RXD) traveling through CN2 are transmitted and received in + / - 12 V to the difference of the signals passing through CN1 who themselves are at TTL level (+ / - 5 V).
The third connector, CN3, 6-pin, for connecting a "chipcard" external to read the SIM cards without using the internal circuit normally dedicated to this task. This option can be very useful when, in particular applications, the modem is installed in a compact package making it difficult to access the location of the SIM card. CN3 manages, among others, the circuits reset (initialization), Clock (clock) and Data I / O (input / output data) and the 5 V supply for the Sim card reader.
The last connector, CN4, 4 pin main power runs from 4.8 to 5.5 volts (current consumption of 360 mA and 36 mA operating at rest). This voltage can be supplied by any power supply or a battery composed of 4 rechargeable batteries.
View of the male connectors 40-pin CN1 and female. 
The connectors Falcom A2 
Table 1 
Table 2 Operation
Regarding the radio part, the oscillator class 4 operates at a frequency of 900 MHz with an RF power of 2 watts (32.5 dBm) radiated on a GSM antenna. Our
modem communicates to 9600 baud (maximum rate for GSM systems) with a data format to 8 bits + 1 stop bit, no parity check or cash flow.
These parameters can be programmed to using the commands "Hayes." Eg AT + IPR Fixed the "baud rate (transmission speed).
Data management is provided through the standard serial port RS232-C, which can be connected either with the CN1 connector (40 pins), or using the connector CN2 (15 pins) as tables provided by the manufacturer. These tables 1 and 2 provide a description of each pin and signal passing through.
"Motherboard" and installation
On this tour, in addition to connectors for connecting the A2, there is also a female DB-9 PCB (RS232-C), a terminal block for power and two RCA jacks for microphone and speaker.
Finally, the printed circuit includes two buttons, one for "reset" (initialization) and the other for the soft-start (boot) and an integrated circuit regulator 5 V for the main voltage. Once the Falcom
2 installed, the modem is ready and can be connected through a cable with an adapter 25 / 9 pin COM port whatsoever.
Power must provide a voltage between 8 and 12 volts and a current of 400 milliamps.
If you intend to use a additional microphone, you can use a simple electret (the classic two-capsule son ...) with the input sensitivity is 10 mV.
If you want to connect an external speaker, it must have an impedance of 50 Ω. The manufacturer's instructions
complete GSM modem Falcom A2 (in English) is available at electronics-magazine.com format. ZIP. It is in the form of a file. PDF along with a ReadMe.
Operation
Let us now leave the modem unit to analyze the pattern shown in Figure 1.
As you can see, we use the connector 40-pin (CN1) for connection of Falcom. This connector is responsible for control and distribution of all signals except the power supply connector CN4 is taken directly out of the integrated circuit regulator U2.
The motherboard is powered by the points + and V by a voltage between 8 and 12 volts. The diode D1 protects the circuit against possible reversals of polarity.
Capacitor C1 filters the blood before it is applied to the input of 7805 (U2). 5 V voltage supplied by the latter also feeds the serial converter TTL/RS232-C (U1), which converts the signals to the channel input connector TXD SERIAL (DB-9) in 0 / 5 V and those retiring in the RXD channel levels of + / - 12 V. U1 is a well known component named MAX32, produced by Maxim.
TXD line modem, pin 27 of the 40 pin connector is connected to pin 11 of U1, which represents the output of the converter RS232-C/TTL, while the RXD line (pin 28) output of the demodulated data, is connected to pin 12 of MAX32 that converts pulse format + / - 12 V.
Here's how the other outputs of the integrated circuit U1.
The RTS, pin 36 of CN1 is connected to pin 10 and exiting through the pin 7, goes to the PC via the DB-9 serial connector. In turn, the PC sends the CTS signal to pin 8 hits in TTL levels (0 / 5 V) through pin 9 to reach, finally, the pin 34 of Falcom A2.
Electrolytic capacitors C3, C4, C5 and C6 are used for internal converters Maxim Integrated circuit for generating, from 5 V, the voltages required to simulate the levels of the RS232-C, which in practice do not exceed 9 V
Continuing Examination of the system, we report the presence of two buttons which are used respectively to initialize and start or shut down the system.
Activation the pusher P1 connected to pin 26 of CN1 connector, makes mass line RsTf and thus causes the initialization of the forced system.
The pusher P2 generates a pulse of 5 V driver, through the pin 29 of CN1, the On / Standby circuit: a first pulse starts the system, the second turns it off, etc ... To complete this analysis
You will notice that the external microphone must be connected between pins 39 (positive electret capsule) and 40 while the speaker uses pins 37 (positive) and 38, always 40-pin connector CN1.
Remember that it is possible to use as microphone, electret capsule conventional two son while the speaker must have an impedance of 50 Ω and support a power of 100 mW.
Notice the dimensions of connectors! 
Figure 1: Diagram of the plate test for GSM modem Falcom A2. 
Figure 2a and 2b: Plot of double-sided printed circuit scale 1. 
GSM Modem Falcom A2. Tiny! 
The plate test completed 
Figure 3: Implementation plan components. To assemble the plate test you can use a double sided PCB with plated through holes. But in our case, having used a 40-pin connector with a pitch of 0.8 mm, it is essential to achieve our next circuit the traditional engraving technique.
Iist
R1: R2
10 kW: 10 kW
C1: 1000 uF 16 V
C2: 1,000 uF 16 V
C3 10 uF 63 V
C4 10 uF 63 V
C5: 10 uF 63 V
C6 10 uF 63 V
D1: 1N4007
U1: U2 MAX32
: 7805
Miscellaneous:
- terminal two locations
- taken BF RCA (2)
- dip-switch or inter-wire (2)
support - 2 x 8 pin ICs
- 10-pin connector PCB
- 4-pin connector strip
- 40 pin AMP connector
-
antenna cable - 12 V
-
serial connector - 15 pin AMP connector cable
-
GSM Antenna - PCB ref. S278
In practice
We can now look after assembling our "cartemère.
Above all, begin to realize the circuit print (Figures 2a and 2b) following your normal procedure.
Once this is done, solder the components in helping you plan the implementation given in Figure 3.
Start with resistors and the diode, taking care to its polarity.
Then, install the support for the MAX32, by arranging the encochedétrompeur to C5.
Continue mounting by soldering all capacitors and install the two buttons for printed circuit and the DB-9 9-pin, making sure it fits comfortably into place before welding.
Then solder a terminal with two poles at 5 mm pitch for power system and do not forget to install two RCA jacks for microphone and any external speaker.
Solder the integrated circuit in 7805 leading his side to the metal block and end with the connector, the most delicate, AMP 40 pin which is connected to the GSM modem.
For this last operation, we recommend you use a soldering iron with a very fine tip and a power of 30 watts max. because the pitch of the pins of this component is only 1 mm!
To power the modem using 4 pin support "tulip" with 2.54 mm to be fit into the connector CN4.
Finish assembly by inserting the MAX32. Set its encochedétrompeur the same side as that of his support and careful not to bend the pins. Last
task, insert the Falcom GSM modem 2 on the connectors and the system is ready for use!
0 comments:
Post a Comment