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Gabriel
Joined: 03 Aug 2009
Posts: 1074
Location: Panama
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| Data Transfer Between PICs - SOLVED!!! |
 Posted: Thu Apr 10, 2025 6:56 am |
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Hi Guys, ive been fighting with this for a few days now. It feels like looking at Schrödinger's cat.
PREMISE:
Im building an application/board where i have 2 PICs - one handles the machine itself, the other handles the HMI for the operator.
the machine PIC reads sensors and said sensor reading need to be displayed on the HMI screen controled by the second processor.
Data needs to be exchanged between the 2 PICs, and ive provided TX/RX lines between them. Harware UARTS on both Processors.
INTENDED SOLUTION:
I am Packing all my variables into a Struct, and then serializing the struct through the UART. Most of these values are FLOATs, and a few flags.
Im using the flags included in the Struct to control flow.
Processor 2 (HMI) sends a byte to Processor 1 (machine) indicating its ready to receive data, Processor 1 updates its sensor values, and shoots out the struct to Processor 2 where its received and the cycle repeats.
im calling this "interbus" - just for clarity on my code/mind.
PROBLEM !!!!:
On Processor 1 while doing my initial tests, i simply initialized my 2 floats as 12.34 and 56.78, simple right.
if i keep these initial conditions, everything works just fine. i get nice flow control, P2 Requests data, P1 received the request and replys. the world is good.
if i send any other values, like ACTUAL sensor readings the serialized struct is completely messed up. the flow control flags turn into wierd values, the float bytes dont make sense on PROCESSOR 1 (Machine) - this is the wierdest thing ever. you can see from my code im tying to print values before and after etc and the values are fine but the serialized data is garbage BEFORE SENDING IT! the problem seems to be on the SENDING side not even on the receiver.
using actual sensor values:
the code runs, i get to the sending part, PRINT MY STRUCT VALUES - they are PERFECT - the serialize the struct into garbage - send garbage, print the struct again, its perfect - the received obviously fails as it got sent garbage.
using fixed values: all is great.
I am pulling my hair out - i know this solution may have its flaws or tricks - this code does not have any checks yet or a CRC which i will include. this right now is just a small scale test, at which i am failing misserably.
if you have easier methods, im all ears.
TESTS:
Ive coded a small sample program. im using a small struct as follows:
Both processors have the same struct.
| Code: | struct P2_Data //DATA FROM P1
{
float P2_Data_1;
float P2_Data_2;
int P2_Data_Ready;
int P2_Interbus_Token;
};
struct P2_Data P2_Sensors; |
defines:
| Code: | #define INTERBUS_SIZE 10
#define OLD_DATA 0xFA
#define NEW_DATA 0xAF
#define DATA_READ 0x5F
#define DATA_REQUESTED 0xF5
#define DATA_SENT 0xAA |
PROCESSOR 2 - HMI:
| Code: |
while(TRUE)
{
delay_ms(500);
if(P1_Sensors.P1_Interbus_Token==DATA_READ) //Previously received data has been read.
{
fprintf(FTDI,"Formal Request\r\n");
P1_Sensors.P1_Interbus_Token=DATA_REQUESTED; //Give Back Token
fputc(P1_Sensors.P1_Interbus_Token,INTER); //Send Token/Request
}
else if(P1_Sensors.P1_Data_Ready==NEW_DATA) //ISR Finished receiving data.
{
fprintf(FTDI,"NEW DATA!!\r\n");
PTR=&P1_Sensors; //Convert from Array to Struct
strcpy(PTR,Serialized);
CLEAR_INTERBUS_BUFFER(); //Clean for next round
PRINT_INTERBUS_BUFFER(); //DEBUG
if(P1_Sensors.P1_Interbus_Token==DATA_SENT) //Check Token is mine now
{
//fprintf(FTDI,"Correct format\r\n");
fprintf(FTDI,"Data1: %3.2f - Data2: %3.2f\r\n",P1_Sensors.P1_Data_1,P1_Sensors.P1_Data_2); //USE DATA
P1_Sensors.P1_Interbus_Token=DATA_READ; //FREE TOKEN
P1_Sensors.P1_Data_Ready=OLD_DATA; //Signal data is OLD
PRINT_INTERBUS_BUFFER(); //DEBUG
}
else fprintf(FTDI,"RDY: %X - TOK: %X\r\n",P1_Sensors.P1_Data_Ready,P1_Sensors.P1_Interbus_Token); //Debug
}
fprintf(FTDI,"RDY: %X - TOK: %X - Index: %u\r\n",P1_Sensors.P1_Data_Ready,P1_Sensors.P1_Interbus_Token,Inter_Index); //Debug
delay_ms(500);
}
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PROCESSOR 1 - MACHINE:
| Code: |
while(TRUE)
{
if(P2_Sensors.P2_Data_Ready==OLD_DATA) //UPDATE SENSORS
{
Get_Pressure(PRESS_3);
Get_Pressure(PRESS_4);
P2_Sensors.P2_Data_1=(float)PSI[PRESS_3].PSI;
P2_Sensors.P2_Data_2=(float)PSI[PRESS_4].PSI;
//P2_Sensors.P2_Data_1=12.34;
//P2_Sensors.P2_Data_2=56.78;
P2_Sensors.P2_Data_Ready=NEW_DATA;
fprintf(FTDI,"DATA1: %3.2f - %3.2f\r\n",P2_Sensors.P2_Data_1,P2_Sensors.P2_Data_2);
fprintf(FTDI,"RDY1: %X - TOK: %X\r\n",P2_Sensors.P2_Data_Ready,P2_Sensors.P2_Interbus_Token);
}
if(P2_Sensors.P2_Interbus_Token==DATA_REQUESTED) //Got Request
{
if(P2_Sensors.P2_Data_Ready==NEW_DATA) //Data is Fresh
{
fprintf(FTDI,"RDY2: %X - TOK: %X\r\n",P2_Sensors.P2_Data_Ready,P2_Sensors.P2_Interbus_Token);
P2_Sensors.P2_Interbus_Token=DATA_SENT; //Give back token
fprintf(FTDI,"DATA1: %3.2f - %3.2f\r\n",P2_Sensors.P2_Data_1,P2_Sensors.P2_Data_2);
fprintf(FTDI,"RDY3: %X - TOK: %X\r\n",P2_Sensors.P2_Data_Ready,P2_Sensors.P2_Interbus_Token);
fprintf(INTER,&P2_Sensors); //Send Data!
fprintf(FTDI,"Requested and sent!\r\n");
PRINT_INTERBUS_BUFFER();
P2_Sensors.P2_Data_Ready=OLD_DATA; //Sent data is old now
fprintf(FTDI,"RDY4: %X - TOK: %X\r\n",P2_Sensors.P2_Data_Ready,P2_Sensors.P2_Interbus_Token);
}
else
{
fprintf(FTDI,"RD5: %X - TOK: %X\r\n",P2_Sensors.P2_Data_Ready,P2_Sensors.P2_Interbus_Token);
P2_Sensors.P2_Data_Ready=OLD_DATA;
}
}
//else
//{
// P2_Sensors.P2_Data_Ready=OLD_DATA;
//}
delay_ms(500);
}
}
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Both PICS are 18F47Q84 - PCH 5.109.
_________________
CCS PCM 5.078 & CCS PCH 5.093
Last edited by Gabriel on Fri Apr 11, 2025 1:30 pm; edited 1 time in total |
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gaugeguy
Joined: 05 Apr 2011
Posts: 327
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| Posted: Thu Apr 10, 2025 8:40 am |
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| Are you sure your sensor data is in the correct float format? |
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Gabriel
Joined: 03 Aug 2009
Posts: 1074
Location: Panama
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| Posted: Thu Apr 10, 2025 9:50 am |
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its a regular PIC float, which i display as %3.2f as usual.
simply doing
Float#1 = Float#2;
Im not using any IEEE formats or anything, just straight CCS floats.
_________________
CCS PCM 5.078 & CCS PCH 5.093 |
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Gabriel
Joined: 03 Aug 2009
Posts: 1074
Location: Panama
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| Posted: Thu Apr 10, 2025 12:35 pm |
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In the code provided im casting an int32 as a float.
I have tried straight float to float, with similar results.
I tried manually writing values and still fails.
_________________
CCS PCM 5.078 & CCS PCH 5.093 |
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jeremiah
Joined: 20 Jul 2010
Posts: 1383
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| Posted: Thu Apr 10, 2025 3:15 pm |
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The first place I would look is:
| Code: |
strcpy(PTR,Serialized);
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If those aren't actually null terminated strings (or incorrectly terminated), then you can start clobbering other variables and even the stack. It'll copy until it finds a value of NULL (0). |
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Jerson
Joined: 31 Jul 2009
Posts: 129
Location: Bombay, India
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| Posted: Thu Apr 10, 2025 8:49 pm |
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Adding to what Jeremiah has stated.
You can use memcpy(&PTR, &Serialized, sizeof(Serialized)) instead of strcpy
Also, rather than have the size of the struct fixed manually, I'd use sizeof(struct P2_data). This removes the chance of human error in calculating the size of the data structure. |
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Gabriel
Joined: 03 Aug 2009
Posts: 1074
Location: Panama
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| Posted: Fri Apr 11, 2025 5:50 am |
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Thank you Jeremia and Jerson!
I will be trying this ASAP!
_________________
CCS PCM 5.078 & CCS PCH 5.093 |
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Gabriel
Joined: 03 Aug 2009
Posts: 1074
Location: Panama
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| Posted: Fri Apr 11, 2025 6:22 am |
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side note: Jerson i see you are from bombay!
I used to spend all my summers(3 Months) there for 5 years! Ive been to every province in India.
learned to jugle in [spam]. mastered Table Tennis in bombay. used to play TT at the Breach Candy Club, and fly kites on a nearby point by the water (forgot the name). i can stil whoop everyones behind on TT with the skills learned there!
awesome place!
ive seen the pics of the beach clean ups, i would love to see that again more than 25 years later...
EDIT: how is "[spam]", the name of an actual place a bad word?
_________________
CCS PCM 5.078 & CCS PCH 5.093 |
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Gabriel
Joined: 03 Aug 2009
Posts: 1074
Location: Panama
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| FROM THE BOTTOM OF MY HEART |
| Posted: Fri Apr 11, 2025 1:30 pm |
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I would like to take a moment to thank you both for the help!
I have clean, fast data, switching processors now thanks to your help.
THANK YOUUUUU!!!!!!!
_________________
CCS PCM 5.078 & CCS PCH 5.093 |
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temtronic
Joined: 01 Jul 2010
Posts: 9457
Location: Greensville,Ontario
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| Posted: Fri Apr 11, 2025 1:44 pm |
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love to see 'SOLVED' in the title but ...
OK.... what was the 'cure' ? |
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Gabriel
Joined: 03 Aug 2009
Posts: 1074
Location: Panama
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| Posted: Fri Apr 11, 2025 3:34 pm |
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Hi Temtronic,
sorry about that, the solution was indeed as sugested by Jeremia and Jerson.
I thought that was fairly obvious.
copying the string to and from the Struct was not being done properly.
using memcpy() instead of strcpy() and giving the functions the proper size of the items as the array and the struct are not null terminated.
_________________
CCS PCM 5.078 & CCS PCH 5.093 |
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Jerson
Joined: 31 Jul 2009
Posts: 129
Location: Bombay, India
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| Posted: Sat Apr 12, 2025 3:45 am |
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Hi Gabriel
Glad to know you still cherish memories of my city. You are perhaps talking about a place called the radio club near marine lines.
You may find it suspicious, but I haven't really been much outside my own city as I am a kind of hermit crab - hehe.
Perhaps you'd like the natural beauty of Goa and Kerala much more.
My city is now more of a concrete jungle with terrible traffic and conjestion - perhaps that is the price of development. I still cherish the good ole days around the 1970s to early 90's
Best wishes
| Gabriel wrote: | side note: Jerson i see you are from bombay!
I used to spend all my summers(3 Months) there for 5 years! Ive been to every province in India.
learned to jugle in [spam]. mastered Table Tennis in bombay. used to play TT at the Breach Candy Club, and fly kites on a nearby point by the water (forgot the name). i can stil whoop everyones behind on TT with the skills learned there!
awesome place!
ive seen the pics of the beach clean ups, i would love to see that again more than 25 years later...
EDIT: how is "[spam]", the name of an actual place a bad word? |
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