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chrisatwan
Joined: 07 Apr 2005
Posts: 3
Location: newark, nj
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| Basic Modbus RTU |
 Posted: Tue Apr 12, 2005 1:48 pm |
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I am sorry. I am just not sure if this should be called when an interrupt occurs or on a timer. Do you call it from another piece of code.
Chris Atwan |
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Mark
Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA
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| Re: Basic Modbus RTU |
| Posted: Tue Apr 12, 2005 2:05 pm |
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| chrisatwan wrote: | I am sorry. I am just not sure if this should be called when an interrupt occurs or on a timer. Do you call it from another piece of code.
Chris Atwan |
You definitely wouldn't call it from an interrupt since the code will enable_interrupts(global). Notice the routine doesn't really do much if Comm1.Packet is not set. This is set from timer1 which is used as a timeout after receiving a byte of data. Since this function is #inline and it checks the Packet flag before doing anything, you want to call this frequently. How frequent? I would do it as often as possible since calling it will do nothing but a couple of bit_tests. You could set a flag when a packet is complete and check that flag but wait, that is actually what the code is doing since it is inline. You could make it just a bit more efficient by handling the Initalized portion yourself and removing it from the service routine. |
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chrisatwan
Joined: 07 Apr 2005
Posts: 3
Location: newark, nj
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| Basic Modbus RTU |
| Posted: Wed Apr 13, 2005 7:22 am |
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I guess I am having so much trouble becuase I am trying to port this code to an Atmel chip. I have no PIC chip or programmer to try this with. It is harder than I thought to do this.
Chris |
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Neutone
Joined: 08 Sep 2003
Posts: 839
Location: Houston
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| Re: Thanks |
| Posted: Wed Apr 13, 2005 3:12 pm |
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| Barney wrote: |
Figure out a way to shoe horn the CRC look up table into the code. |
You could use the bit shift method in the first post in this thread. It's much smaller. |
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Barney
Joined: 18 Oct 2004
Posts: 41
Location: Newark, CA
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| Posted: Thu Apr 14, 2005 12:58 pm |
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| Yep, that is what I am doing. But I am an efficiency freak and I don't like having my MPU wasting clock cycles if I don't have to. So for now I am using the bit shift algorithm and looking for a way to move to the table look up. |
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Pbernardi
Joined: 14 Sep 2005
Posts: 12
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| Posted: Mon Jun 26, 2006 2:24 pm |
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Hi,
Reviving the topic.
I�ve tried to use the Neutone�s Code in a PIC18F452 with PCH 2.234, and I use the ModBusView (www.oceancontrols.com.au) to try to communicate to my PC.
I used the following code:
| Code: |
void main()
{
config();
COMM1.Network_Address = 1;
Registry_Map[1] = 23; //a debug value
while(1)
{
COMM1_Service();
}
}
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But it doens�t seem alive; The ModBusView accuses TimeOut.
The #Fuses and PIC configurations are OK, there is some code running, and I created this code just for testing.
The PIC appears receive data; The variable COMM1_Buffer usually is somethink like {0xCE,0x80,0x01}, but I�ve not seen it receiving more than 3 words.
Any idea?
Paulo Bernardi.
_________________
Paulo Bernardi |
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Pbernardi
Joined: 14 Sep 2005
Posts: 12
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| Posted: Tue Jun 27, 2006 8:11 am |
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Hi,
I changed this page code by by code library�s code (http://www.ccsinfo.com/forum/viewtopic.php?t=19306&highlight=modbus) that looks more complete.
Debugging my code, I see that the master�s chars are coming, but the CRC isn�t working weel.
the master sends : [01][03][00][00][00][0A][C5][CD], I receive this, but the CRC ([C5][CD]) isn�t the same of the program (that changes everytime)
So, the program discards the data and receive a new one, and discars and receive other... with no response.
Does anybore can help me?
_________________
Paulo Bernardi |
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Neutone
Joined: 08 Sep 2003
Posts: 839
Location: Houston
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| Posted: Wed Jun 28, 2006 9:22 am |
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| It's been a long time since that code was posted. If you find a bug in the code library please post how you fixed it. The code I posted was written to demonstrate a method. The flow of the code is right. It's not the code I actually used real products because I don't own that code. |
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Pbernardi
Joined: 14 Sep 2005
Posts: 12
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| Posted: Wed Jun 28, 2006 10:35 am |
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Neutone,
Thanks for reply.
I�ve found a little mistake on your code, after change it worked.
| Code: | /****************************************************/
/* Mean time to decode CRC ~ xxuS per byte */
/****************************************************/
COMM1.CRClo_Index=Comm1.CRChi_Index-1; // Solve this index once instead of once per byte
Comm1.Index = 0; // Start at begining of packet
COMM1.CRC_Lo = COMM1.CRC_Hi = 0xFF; // Prepare to CRC (missing on original code)
while(Comm1.Index < COMM1.CRClo_Index) // Use all bytes prior to CRClo_Index
{ Comm1.Table_Index = COMM1_Buffer[Comm1.Index]; // Generate CRC
Comm1.Table_Index ^= Comm1.CRC_Lo; // Generate CRC
Comm1.CRC_Lo = Table_CRC_Hi[Comm1.Table_Index]; // Generate CRC
Comm1.CRC_Lo ^= Comm1.CRC_Hi; // Generate CRC
Comm1.CRC_Hi = Table_CRC_Lo[Comm1.Table_Index]; // Generate CRC
Comm1.Index++;
} |
But wasn�t it the real problem. It was a strange behavior (bug?) using this code on PIC18F452. When I declared:
| Code: | | char Table_CRC_Lo[256] |
It didn�t work well. But using:
| Code: | | const char Table_CRC_Lo[256] |
 It worked fine. Why? I don�t kwon.. 
_________________
Paulo Bernardi |
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Guest
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| Posted: Mon Jul 10, 2006 5:14 pm |
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But wasn�t it the real problem. It was a strange behavior (bug?) using this code on PIC18F452. When I declared:
| Code: | | char Table_CRC_Lo[256] |
It didn�t work well. But using:
| Code: | | const char Table_CRC_Lo[256] |
It worked fine. Why? I don�t kwon.. [/quote]
It�s easy... when you put char Table_CRC_Lo[256] the array is allocated in RAM, but when you use const char Table_CRC_Lo[256] it�s created in ROM (program FLASH, in reality). So if you are using a lot of the 18F452 RAM, it can easylly overflow and not compile. |
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buneri
Joined: 23 Aug 2007
Posts: 14
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| How to access 43001 Adress |
| Posted: Fri Nov 02, 2007 12:25 am |
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Int16 Registry_Map[128];
#locate Registry_Map = 0x200
Int8 REG_Map[256];
#locate REG_Map = Registry_Map
Int16 Recieved_Packets; // Accessed in holding register 400001 via MODBUS
#locate Recieved_Packets = Registry_Map
Int16 Reply_Packets_This_Second; // Accessed in holding register 400002 via MODBUS
#locate Reply_Packets_This_Second = Registry_Map + 2
In the above coding you have accessed the input registers at 40001 and 40002.
I want to read or write the input registers at 43001 onward in slave.
What will be the code for that?
Plz tell me in hurry |
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Neutone
Joined: 08 Sep 2003
Posts: 839
Location: Houston
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| Re: How to access 43001 Adress |
| Posted: Fri Nov 02, 2007 4:05 pm |
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| buneri wrote: | Int16 Registry_Map[128];
#locate Registry_Map = 0x200
Int8 REG_Map[256];
#locate REG_Map = Registry_Map
Int16 Recieved_Packets; // Accessed in holding register 400001 via MODBUS
#locate Recieved_Packets = Registry_Map
Int16 Reply_Packets_This_Second; // Accessed in holding register 400002 via MODBUS
#locate Reply_Packets_This_Second = Registry_Map + 2
In the above coding you have accessed the input registers at 40001 and 40002.
I want to read or write the input registers at 43001 onward in slave.
What will be the code for that?
Plz tell me in hurry |
When you decode the packet subtract 3000 from the register address. That will return the value at Registry_Map[0] as 43001. You will be limited to 128 sequential register addresses. |
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buneri
Joined: 23 Aug 2007
Posts: 14
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| How to access adress 43001 |
| Posted: Sat Nov 03, 2007 1:03 am |
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Thank You very much for fast response,
I dont understand, how it would be possible to locate 3001 adress location in PIC16f877A since it has very limitted memory.
If it is possible what technique i should use to solve my problem. Please reply with detail and clear.I dont understand ur previous point.
I m waiting 4 ur response.
Thanks |
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