Sometimes we need to have sensors away of the raspberry PI and we need to connect them without too many wires.
I decide to use a small cpu like the PIC12F1840 which will have only 2 IO but could be daizy chain up to 127 modules using a simple RJ11 cable system. This is the same plug we use to connect telephone.
I was able to set different type of operation using the same binary code. This way we could set them online.
But since modbus protocol need to have a different slave address for each module, we need to set the address one by one.
This is the primary documentation about it
https://docs.google.com/document/d/1Nex ... sp=sharing
it is base on my preliminary water detect module
https://docs.google.com/document/d/1YN4 ... sp=sharing
The document explain acces via minimalmodbus in python.
But it is possible to use libmodbus in C. In my test , python will gives you around 20 transactions per second
but libmodbus will be around 200 with a Baud Rate of 57600.
This is the configuration application in C to select Slave address and IO configuration
you will need to install libmodbus
Code: Select all
sudo apt-get install libmodbus5 libmodbus-devCode: Select all
gcc -I /usr/include/modbus configPIC.c -o configPIC -l modbusCode: Select all
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <termios.h>
#include <modbus.h>
typedef struct
{
unsigned short mode;
unsigned char * asciiMode;
}IOConfigStruct;
char device[256];
int Baud = 57600;
unsigned char scanOnly=0;
unsigned char CurrentSlaveAddress=255;
int IsModuleFound(modbus_t * mb, unsigned char SlaveAddress);
unsigned char selectModule(modbus_t * mb);
IOConfigStruct configInfo[]={
{ 0, "ANALOGVDD"},
{ 1, "ANALOG1V"},
{ 2, "ANALOG2V"},
{ 3, "ANALOG4V"},
{ 4, "INPUT"},
{ 5, "INPUT PULLUP"},
{ 6, "OUTPUT"},
{ 8, "CAP SENSE OFF"},
{ 9, "CAP SENSE LOW"},
{ 10, "CAP SENSE MEDIUM"},
{ 11, "CAP SENSE HIGH"},
{ 16, "DHT11"},
{ 17, "DHT22"},
{ 32, "DS18B20"},
{ 64, "R/C SERVO"},
{128, "COUNTER"},
{65535, NULL}};
int IsConfigModeValid(int mode)
{
int loop;
for(loop=0;;loop++)
{
if(configInfo[loop].mode==65535) break;
if(configInfo[loop].mode==mode) return 1;
}
return 0;
}
char * configModeInText(int IOConfigMode)
{
int loop;
for(loop=0;;loop++)
{
if(configInfo[loop].mode==65535)
break;
if(configInfo[loop].mode== IOConfigMode)
return configInfo[loop].asciiMode;
}
return "???";
}
void decodeArg(int argc, char * argv[])
{
int loop;
for(loop=1;loop<argc;loop++)
{
if(strcasecmp(argv[loop],"-scan")==0)
scanOnly=1;
if(strcmp(argv[loop],"-d")==0)
{
loop++;
strcpy(device,argv[loop]);
}
if(strcmp(argv[loop],"-b")==0)
{
loop++;
Baud=atoi(argv[loop]);
}
if(strcmp(argv[loop],"--help")==0)
{
printf("usage:\nconfigPIC [-scan][-d DeviceName][-b BaudRate]\n");
exit(0);
}
}
}
void changeAddress(modbus_t * mb)
{
int new_Address;
printf("\n=======Change Address\n");
if(CurrentSlaveAddress == 255)
selectModule(mb);
else
if(!IsModuleFound(mb,CurrentSlaveAddress))
selectModule(mb);
if(CurrentSlaveAddress==255) return;
printf("\nEnter new Slave Address for this module (1..127) ?");
if(scanf("%d",&new_Address)!=1)
printf("Invalid value! configuration not change.\n");
else
{
if(new_Address>0)
if(new_Address<128)
{
if(IsModuleFound(mb,new_Address))
{
modbus_set_slave(mb,CurrentSlaveAddress);
printf("Address already used!\nConfiguration not changes.\n");
}
else
{
modbus_set_slave(mb,CurrentSlaveAddress);
modbus_write_register(mb,160,new_Address);
printf("Module is now on Address %d\n",new_Address);
CurrentSlaveAddress=new_Address;
}
}
else
printf("Invalid value! configuration not change.\n");
}
usleep(1000000); // delay needed to store data into eerom
IsModuleFound(mb,CurrentSlaveAddress);
}
unsigned short getConfigMode(modbus_t * mb, int Pin)
{
uint16_t MB_Register;
if( modbus_read_registers(mb,0x100+Pin,1,&MB_Register) < 0)
return 65535;
return MB_Register;
}
int IsModuleFound(modbus_t * mb, unsigned char SlaveAddress)
{
uint16_t MB_Register;
int rcode;
if(SlaveAddress >127) return 0;
modbus_set_slave(mb,SlaveAddress);
if (modbus_read_registers(mb,251,1,&MB_Register) <0) return 0;
if(MB_Register != 0x6532)
return 0;
return 1;
}
unsigned char selectModule(modbus_t * mb)
{
char buffer[256];
int SlaveAddress;
int rcode;
uint16_t MB_Register;
CurrentSlaveAddress=255;
printf("Select Module\nEnter Slave Address ?");
if(scanf("%d",&SlaveAddress)==1)
if(SlaveAddress>0)
if(SlaveAddress<128)
if(IsModuleFound(mb,SlaveAddress))
CurrentSlaveAddress=SlaveAddress;
printf("\n");fflush(stdout);
return SlaveAddress;
}
void changeConfigMode(modbus_t * mb,int Pin)
{
int loop;
unsigned short mode;
unsigned char module;
int new_mode;
uint16_t MB_mode;
printf("\n======= Change IO%d mode\n",Pin);
if(CurrentSlaveAddress == 255)
selectModule(mb);
else
if(!IsModuleFound(mb,CurrentSlaveAddress))
selectModule(mb);
if(CurrentSlaveAddress==255) return;
for(loop=0;;loop++)
{
if(configInfo[loop].mode==65535) break;
if(loop%3==0)
printf("\n");
printf("%3d) %-20s",configInfo[loop].mode, configInfo[loop].asciiMode);
}
mode=getConfigMode(mb,Pin);
printf("\n\nSlave address %d current IO%d mode is %d : %-20s\n",CurrentSlaveAddress,Pin,mode,configModeInText(mode));
printf("\nEnter new configuration ?");
if(scanf("%d",&new_mode)!=1)
printf("Invalid value! configuration not change.\n");
else
{
if(IsConfigModeValid(new_mode))
{
MB_mode= new_mode;
modbus_write_register(mb,0x100+Pin,MB_mode);
printf("Module %d IO%d set to %d: %s\n",CurrentSlaveAddress,Pin,MB_mode,configModeInText(MB_mode));
}
else
printf("Invalid value! configuration not change.\n");
}
usleep(1000000); // delay needed to store data into eerom
}
void scanBus(modbus_t * mb)
{
int loop,io;
int rcode;
uint16_t MB_Register;
//set 1/100th of second response time
struct timeval response;
response.tv_sec=0;
response.tv_usec=10000;
modbus_set_response_timeout(mb, &response);
printf("\n==== Scanning MODBUS\n");fflush(stdout);
for(loop=1;loop<128;loop++)
{
if(IsModuleFound(mb,loop))
{
printf("%d : %-20s",loop,"PIC Multi-Purpose");
for(io=0;io<2;io++)
{
printf("IO%d: ",io);
printf("%-20s",configModeInText(getConfigMode(mb,io)));
}
printf("\n");
}
}
}
unsigned char ReadOneKey(void)
{
char c;
struct termios term,term_orig;
// put keyboard in raw mode
tcgetattr(0,&term_orig);
memcpy(&term,&term_orig,sizeof(struct termios));
term.c_lflag &= ~(ICANON | ECHO);
term.c_cc[VTIME] =0;
term.c_cc[VMIN]=1;
tcsetattr(0,TCSANOW, &term);
while(read(0, &c,1)!=1);
tcsetattr(0,TCSANOW,&term_orig);
fflush(stdin);
return c;
}
void Menu(modbus_t * mb)
{
char rcode;
printf("\nPIC multi-purpose I/O MODBUS configuration\n");
printf("Version 1.0 (c) Daniel Perron, April 2014\n");
printf("device:%s Baud Rate:%d\n",device,Baud);
while(1)
{
// print menu
printf("\n\n\nM) MODBUS scan \n");
printf("S) Select Slave Module\n");
printf("A) Change Slave Address\n");
printf("0) Set IO0 mode\n");
printf("1) Set IO1 mode\n");
printf("Q) Quit\n");
printf("\nSelected module :");
if(CurrentSlaveAddress == 255)
printf("None\n");
else
printf("%d\n",CurrentSlaveAddress);
fflush(stdout);
rcode= toupper(ReadOneKey());
fflush(stdin);
switch(rcode)
{
case 'M': scanBus(mb);break;
case 'S': selectModule(mb);break;
case 'A': changeAddress(mb);break;
case '0': changeConfigMode(mb,0);break;
case '1': changeConfigMode(mb,1);break;
case 'Q': return;
}
}
}
int main(int argc, char * argv[])
{
modbus_t *mb;
strcpy(device,"/dev/ttyAMA0");
decodeArg(argc,argv);
mb = modbus_new_rtu(device,Baud,'N',8,1);
modbus_connect(mb);
if(scanOnly==1)
scanBus(mb);
else
Menu(mb);
modbus_close(mb);
modbus_free(mb);
return 0;
}
Daniel
