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meereck
Joined: 09 Nov 2006
Posts: 173
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| how to implement a device with AT command interface |
 Posted: Fri Nov 21, 2008 4:35 pm |
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Hello,
my intent is to develop a device which responds to sort of AT-commands via its serial line. I would like to set and get settings which will be stored in internal EEPROM with the help of those commands.
Example:
1) I want to set the attribute "speed" to the value of 10 by sending "speed 10\n" to the device.
2) I want to get the same attribute by sending (speed\n), the device should reply "speed=10\n"
3) all values will be stored in internal eeprom when "write\n" command has been issued.
Basically, I will do something like this:
| Code: | #int_rda
void serreceive()
{
char c;
c=getc();
if(c=='\n')ProcessBuffer();
else
{
// fill the buffer and overflow protection....
}
} |
My question is what is the easiest way how to deal with the incoming buffer?
Is the only way using strcmp(parsed_buf,"speed")? I would take too many "if, else if" etc.
For saving entire "configuration" into the internal eeprom - is there any way how to make it "automatic". I mean to write/read those values in a "for" loop? Majority of them will be int8 and int16. Or would it ease it up by using structures?
Thank you for any help,
meereck |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Fri Nov 21, 2008 5:03 pm |
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| Quote: |
My question is what is the easiest way how to deal with the incoming buffer?
Is the only way using strcmp(parsed_buf,"speed")? I would take too many "if, else if" etc.
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Look at Ttelmah's method for detecting a match between incoming
commands and strings stored in a table:
http://www.ccsinfo.com/forum/viewtopic.php?t=31144 |
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meereck
Joined: 09 Nov 2006
Posts: 173
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| Posted: Sun Nov 23, 2008 4:24 am |
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Hello, thank you. It looks straight-forward.
Any idea about saving plenty of variables into EEPROM memory? I was thinking about an array and variables in "union" . The array would be used for cyclic reading/writing into the EEPROM. Is it feasible this way? I dont know much about union type.
have a nice weekend,
M. |
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Ttelmah
Guest
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| Posted: Sun Nov 23, 2008 3:46 pm |
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A union, allows two different variables to reside in the same RAM space.
You could (for instance), have a declaration like:
| Code: |
struct data_layout {
int8 avalue[2];
int16 a16bitvalue;
float afloatvalue;
int16 anothervalue;
float asecondfloat;
int16 afinal16bitvalue;
};
union {
int8 b[16];
int16 i[8]
float vals[4];
struct data_layout d;
} fred;
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Then talk to the four floating point numbers 'fred.vals[0..3]', or to the bytes representing these numbers as 'fred.b[0..15]'. Also though, to the parts of the 'data_layout' structure, as: 'fred.d.afloatvalue' for example.
It is 'great' for sending numbers of one type across RS232 for example, and then re-assembling them into a different type (send fred.b[0...15], but access the floats locally for example).
However, for simply storing a data structure into/out of the EEPROM, an integer pointer is probably simpler.
So [for instance]:
| Code: |
void EEPROM_GET(int *ptr,int num,int addr) {
int count;
for (count=0;count<num;count++)
{
ptr[count]=READ_EEPROM(addr+count);
}
}
void EEPROM_PUT(int *ptr,int num,int addr) {
int count;
for (count=0;count<num;count++)
{
WRITE_EEPROM(addr+count,ptr[count]);
}
}
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Then if you have a data structure containing your configuration information, called 'config', you can write this to the start of the EEPROM, using:
EEPROM_PUT(&config,sizeof(config),0);
and load it with the equivalent 'get'.
If you want to load a second structure, the same call, but with the last number (the EEPROM start address), set to the 'sizeof' the first stucture, handles this.
I don't really think a union 'helps' for this.
Best Wishes |
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meereck
Joined: 09 Nov 2006
Posts: 173
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| Posted: Sun Nov 23, 2008 5:06 pm |
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If I could, I would issue Ttelmah.Karma=KARMA_MAX
Thanks a lot for the explanation. It is crystal clear now.
I will post my entire source code once it has been finished and debugged.
Meereck |
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meereck
Joined: 09 Nov 2006
Posts: 173
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| Posted: Wed Dec 03, 2008 10:20 am |
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Hello again, I tried that "union" stuff (Intending to send that VehicleBuffer array over RS-232 (I hope that "BinarySendVehicle" is ok)), but it does not work as you wrote:
| Code: |
struct _Vehicle{
unsigned int32 DateTime;
unsigned int16 LaneLength;
char Speed;
};
union Veh{
int8 bytes[7];
struct _Vehicle vehicle;
};
Veh VehicleBuffer[VEHICLE_BUFFER_LENGTH]; // i get error : expecting a (
void BinarySendVehicle(unsigned int16 index)
{
char i;
for(i=0;i<7;i++)fputc(VehicleBuffer[index].bytes[i],RS232);
}
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EDIT: I was seaching the forum, and found some source codes with "typedef". The following gets compiled without any errors (though dont understand why typedef helps)
| Code: | typedef union {
int8 bytes[7];
struct {
unsigned int32 DateTime;
unsigned int16 LaneLength; // lower 12 bits = length in cm, higher 4 bits=lane
char Speed;
} vehicle;
} Vehicle;
//Now declare the array
Vehicle VehicleBuffer[VEHICLE_BUFFER_LENGTH]; |
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