I am trying to recieve 1 character using the USART feature on PIC 16.
Both the transmitter and receiver are both PIC 16s.
Can i check if the way to call the receive function is correct conceptually
char tmp;
CREN = 0;
CREN = 1;
while(!RCIF);
if(OERR==1)
{
tmp = RCREG;
tmp = RCREG;
CREN=0;
DelayMs(5);
CREN=1;
}
else
{
tmp = RCREG;
}
CREN = 0;
Many thanks in advance!
You must first initiate the UART.
Load into SPBRG register proper
number depend on your baud
rate and CPU clock frequency
(check datasheet).
Set BRGH bit in register TXSTA depend on desired baud rate generator (check datasheet).
Set bits in RCSTA register depend on data length and so on (check datasheet). Enable CREN bit in RCSTA register.
Wait on PIR1.RCIF == 1 bit which indicate that buffer receiver is full (only one byte).
Related
I am using NodeMCU & Energy meter. Energy meter is Modbus RTU device which display parameter in 32 bit. With below piece of code I could able to read the data from slave but need method to type cast from into 32 bit floating & display
When I change the value to unsigned decimal in ModScan software the values showing properly. But I need to display value in 32 bit floating point.
#include <ModbusMaster232.h>
#include <SoftwareSerial.h>
float data[100];
ModbusMaster232 node(1);
// Define one address for reading
#define address 1
// Define the number of bits to read
#define bitQty 70
void setup()
{
Serial.begin(9600);
// Initialize Modbus communication baud rate
node.begin(9600);
}
void loop()
{
int result = node.readHoldingRegisters(address, bitQty);
data[0] = (float)node.getResponseBuffer(0);
data[1] = (float)node.getResponseBuffer(1);
data[2] = (float)node.getResponseBuffer(2);
data[3] = (float)node.getResponseBuffer(3);
data[4] = (float)node.getResponseBuffer(4);
data[5] = (float)node.getResponseBuffer(5);
for (int i = 0; i < 100; i++)
{
//data[i] = node.getResponseBuffer(i);
Serial.println(data[i]);
}
Serial.println("............");
}
I would like to display the reading as shown in Modbus with type casting.
Actual Modbus device output from salve:
Arduino output while read data from energy meter:
You are casting a 16-bit word into a float. Check the slave documentation to find how they map a 32-bit floating point into two Modbus registers. Basically you need to know where the least significant word is (first or second register), load them into memory (shift if necessary) and cast to float.
I am looking and trying to solve exact same problem (with same results). This may help:
function read() {
client.readHoldingRegisters(0000, 12)
.then(function(d) {
var floatA = d.buffer.readFloatBE(0);
console.log("Total kWh: ", floatA); })
.catch(function(e) {
console.log(e.message); })
.then(close);
}
This is NodeJS and javascript version, which works and Arduino does not. Complete example can be found here and it works on Raspberry Pi https://github.com/yaacov/node-modbus-serial/blob/master/examples/buffer.js
Examples of writing to a port seem to always use the port number as a constant, eg,
OCR2A = 180;
How do you write to the port when the port is unknown until run time. For example,
int port = (buttonPressed) ? 0x3b : 0x3c;
portWrite( port, 180 );
What I cannot find is the funtion portWrite(). Does something like that exist?
Robert's answer has some imprecise assertions and an incomplete answer.
Writing directly to port registers you can ruin other settings of the port and sometimes cause permanent damage to controller.
Can ruin other settings: true, you have to know what you are doing (for instance what pins are on the port you are manipulating, and know what are the functions you want to keep.
Can cause permanent damage: not really, or better not because of the port manipulation. If you wire a short circuit to ground and then set it as an output to 1, you can damage it whether you are using the port register or the digitalwrite. You have to be careful in both ways.
Now, returning to your problem, the enumeration is one way, but since the PORTB, PORTC, PORTD are just short name for values, you can set a variable and then use it to indirectly access it.
The type for this kind of variable is a volatile pointer to a byte (volatile means that write and read operations cannot be optimized by the compiler, since the value can change even between two operations):
volatile uint8_t *variablePortRegister;
You just have to load it with the address (so with the & symbol) of the register you want to change:
variablePortRegister = &PORTC;
then use the pointer to change the value
PORTC = 0x12;
becomes
(*variablePortRegister) = 0x12;
This is a short example. For it to work, connect a LED with resistor on arduino pin 5 (bit 5 of PORTD). The LED on the board (labeled L) is connected to pin 13 (bit 5 of PORTB).
The sketch will make one of the two leds blink for five times, then switch to the other. Only port manipulation instructions are used, and you can find that the way to read the port is the same as the one to write it.
volatile uint8_t *myportreg;
unsigned long lastTime;
uint8_t counter;
void setup() {
DDRB |= 0x20;
DDRD |= 0x20;
PORTB = 0;
PORTD = 0;
counter = 99; // trigger the register change immediately
}
void loop() {
if (counter >= 10)
{
counter = 0;
if (myportreg == &PORTD)
myportreg = &PORTB;
else
myportreg = &PORTD;
}
if ((millis() - lastTime) > 500)
{
lastTime = millis();
// change bit 5 of register
*myportreg = 0x20 ^ (*myportreg);
counter++;
}
}
EDIT: as Robert pointed out, it's much better to "use" just the pins you need (in this case, bit 5 of port B and D) rather than setting the whole port; this way you minimize the risk of screwing up something else. This edit is already included in the above code, so the code is correct
The port is a bit in one particular register. If you know the register and the position of the port in that particular register you can try this:
register = (1<<port) || register
to set the port to 1 and
register = (1<<port)^-1 && register
to set the port to 0.
Of course, you will need a switch somewhere to determine the register and the bit of the port in the register given the port name.
I need to transfer data serially from AT89s52 to Hyperterminal of PC.
For that I made a sample program to print "Hello" on the hyperterminal of my PC by programming the below given code inside 89s52 microcontroller and connecting it to my PC via serial port. Now when I am opening hyperterminal for the respective port, I should be seeing "Hello" printed on the screen multiple times, but what actually I am seeing is some garbage data getting printed.
This is the code I have used.
#include < AT89X52.H>
#include < STDLIB.H>
#include < STDIO.H>
unsigned int i;
void main (void)
{
TMOD = 0x20;
SCON = 0x50;
TH1 = 0xFD;
TL1 = 0xFD;
TR1 = 1;
TI = 1;
P1 = 0;
while (1)
{
puts("Hello\r");
P1 ^= 0x01; /* Toggle P1.0 each time we print */
for(i=0;i<25000;i++);
}
}
In the Hyper terminal I am not getting correct output i.e. Hello. Instead I am seeing some Garbage characters..
Can anybody help on this please..?
Can you See P1 is toggling? I would rather send a single character first and observe what is sending by using an oscilloscope. You should see a digital signal corresponding to the ASCII value of the character being split-out from the TX pin of the micro. Also you can check the baud rate (exact value) by using the scope. If you are convinced that the correct value is sent at the right baud rate it is most likely that you got a bad connection or perhaps the baud rate should slightly be changed.
I try to send the data from pc to the pic microcontroller. I am a beginner in PIC.
I send the data from hyperterminal and the data will display in the led in port B of PIC.
I used 10Mhz clock and the connection in 9600 baudrate.
here my uart.h program:
char UART_Init(const long int baudrate)
{
unsigned int x;
x = (_XTAL_FREQ - baudrate*64)/(baudrate*64);
if(x>255)
{
x = (_XTAL_FREQ - baudrate*16)/(baudrate*16);
BRGH = 1;
}
if(x<256)
{
SPBRG = x;
SYNC = 0;
SPEN = 1;
TRISC7 = 1;
TRISC6 = 1;
CREN = 1;
TXEN = 1;
return 1;
}
return 0;
}
char UART_TX_Empty()
{
return TRMT;
}
char UART_Data_Ready()
{
return RCIF;
}
char UART_Read()
{
while(!RCIF);
return RCREG;
}
void UART_Read_Text(char *Output, unsigned int length)
{
int i;
for(int i=0;i<length;i++)
Output[i] = UART_Read();
}
void UART_Write(char data)
{
while(!TRMT);
TXREG = data;
}
void UART_Write_Text(char *text)
{
int i;
for(i=0;text[i]!='\0';i++)
UART_Write(text[i]);
}
and this is my main program:
#include<htc.h>
#include<pic.h>
#define _XTAL_FREQ 10000000 //Clock Frequency
#include "uart.h"
void main()
{
TRISB = 0x00; //PORTB as Output
UART_Init(9600);
do
{
if(UART_Data_Ready())
PORTB = UART_Read();
__delay_ms(1000);
}while(1);
}
in hyperteminal I send data say 10010010 but the led in port B do not respond, are there any error in my program?
You have several steps: initialize UART, initialize LEDs, communicate over UART and setup your PC's UART. Which components have you successfully written and tested? You say you're a beginner, so what is the smallest functional program you have successfully executed on a PIC? I've been working with microcontrollers for years, but I still schedule about a whole day to get a single LED to turn on because it could be a software problem, a hardware problem, a voltage problem, an oscillator problem, a PCB problem or a compiler problem.
Here are the steps I take for microchip bring up:
Go over the oscillator section, the configuration bits section, the watchdog section and the pinout section (looking for VDD and VSS) in the datasheet. These are some of the hardest parts to get right. (A gotcha about the oscillator: just because you can program a chip, doesn't mean the oscillator is working because the programmer provides it's own clock.)
Write the bare-minimum code to turn on a single LED.
Write the bare-minimum code to make the LED blink (just use a for-loop delay for now, timers come later)
Write UART initialization code and transmit a single character, I use captial U because it's pretty in binary. TXREG = 'U';
Connect the UART to a PC and see if the hyperterminal sees the U. If it doesn't, I connect an oscilscope to the lines to make sure that the PIC is transmitting, that the PC transmits when I type characters and that the timing of the edges matches.
Within the PIC code, have the UART echo characters from the terminal. (TXREG = RXREG;), and then type on the hyperterminal and make sure the characters are echoed back.
One more note:
Do not have the PIC perform the SPBRG calculation. PIC16 are 8-bit processors and 10000000 requires 32-bits to store. There might be hiccups with the integer divison. It might not have a bug in it, but there's no need to have the PIC calculate it each time. Calculate it before-hand and hard-code the value.
I am trying to program a MSP430 with a simple "FIR filter" program, that looks like the following:
#include "msp430x22x4.h"
#include "legacymsp430.h"
#define FILTER_LENGTH 4
#define TimerA_counter_value 12000 // 12000 counts/s -> 12000 counts ~ 1 Hz
int i;
double x[FILTER_LENGTH+1] = {0,0,0,0,0};
double y = 0;
double b[FILTER_LENGTH+1] = {0.0338, 0.2401, 0.4521, 0.2401, 0.0338};
signed char floor_and_convert(double y);
void setup(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop WDT
BCSCTL1 = CALBC1_8MHZ; // Set DCO
DCOCTL = CALDCO_8MHZ;
/* Setup Port 3 */
P3SEL |= BIT4 + BIT5; // P3.4,5 = USART0 TXD/RXD
P3DIR |= BIT4; // P3.4 output direction
/* UART */
UCA0CTL1 = UCSSEL_2; // SMCLK
UCA0BR0 = 0x41; // 9600 baud from 8Mhz
UCA0BR1 = 0x3;
UCA0MCTL = UCBRS_2;
UCA0CTL1 &= ~UCSWRST; // **Initialize USCI state machine**
IE2 |= UCA0RXIE; // Enable USCI_A0 RX interrupt
/* Setup TimerA */
BCSCTL3 |= LFXT1S_2; // LFXT1S_2: Mode 2 for LFXT1 = VLO
// VLO provides a typical frequency of 12kHz
TACCTL0 = CCIE; // TACCR0 Capture/compare interrupt enable
TACCR0 = TimerA_counter_value; // Timer A Capture/Compare 0: -> 25 Hz
TACTL = TASSEL_1; // TASSEL_1: Timer A clock source select: 1 - ACLK
TACTL |= MC_1; // Start Timer_A in up mode
__enable_interrupt();
}
void main(void) // Beginning of program
{
setup(); // Call Function setup (see above)
_BIS_SR(LPM3_bits); // Enter LPM0
}
/* USCIA interrupt service routine */
/*#pragma vector=USCIAB0RX_VECTOR;*/
/*__interrupt void USCI0RX_ISR(void)*/
interrupt (USCIAB0RX_VECTOR) USCI0RX_ISR(void)
{
TACTL |= MC_1; // Start Timer_A in up mode
x[0] = (double)((signed char)UCA0RXBUF); // Read received sample and perform type casts
y = 0;
for(i = 0;i <= FILTER_LENGTH;i++) // Run FIR filter for each received sample
{
y += b[i]*x[i];
}
for(i = FILTER_LENGTH-1;i >= 0;i--) // Roll x array in order to hold old sample inputs
{
x[i+1] = x[i];
}
while (!(IFG2&UCA0TXIFG)); // Wait until USART0 TX buffer is ready?
UCA0TXBUF = (signed char) y;
TACTL |= TACLR; // Clear TimerA (prevent interrupt during receive)
}
/* Timer A interrupt service routine */
/*#pragma vector=TIMERA0_VECTOR;*/
/*__interrupt void TimerA_ISR (void)*/
interrupt (TIMERA0_VECTOR) TimerA_ISR(void)
{
for(i = 0;i <= FILTER_LENGTH;i++) // Clear x array if no data has arrived after 1 sec
{
x[i] = 0;
}
TACTL &= ~MC_1; // Stops TimerA
}
The program interacts with a MatLab code, that sends 200 doubles to the MSP, for processing in the FIR filter. My problem is, that the MSP is not able to deal with the doubles.
I am using the MSPGCC to compile the code. When I send a int to the MSP it will respond be sending a int back again.
Your problem looks like it is in the way that the data is being sent to the MSP.
The communications from MATLAB is, according to your code, a sequence of 4 binary byte values that you then take from the serial port and cast it straight to a double. The value coming in will have a range -128 to +127.
If your source data is any other data size then your program will be broken. If your data source is providing binary "double" data then each value may be 4 or 8 bytes long depending upon its internal data representation. Sending one of these values over the serial port will be interpreted by the MSP as a full set of 4 input samples, resulting in absolute garbage for a set of answers.
The really big question is WHY ON EARTH ARE YOU DOING THIS IN FLOATING POINT - on a 16 bit integer processor that (many versions) have integer multiplier hardware.
As Ian said, You're taking an 8bit value (UCA0RXBUF is only 8 bits wide anyway) and expecting to get a 32bit or 64 bit value out of it.
In order to get a proper sample you would need to read UCA0RXBUF multiple times and then concatenate each 8 bit value into 32/64 bits which you then would cast to a double.
Like Ian I would also question the wisdom of doing floating point math in a Low power embedded microcontroller. This type of task is much better suited to a DSP.
At least you should use fixed point math, seewikipedia (even in a DSP you would use fixed point arithmetic).
Hmm. Actually the code is made of my teacher, I'm just trying to make it work on my Mac, and not in AIR :-)
MATLAB code is like this:
function FilterTest(comport)
Fs = 100; % Sampling Frequency
Ts = 1/Fs; % Sampling Periode
L = 200; % Number of samples
N = 4; % Filter order
Fcut = 5; % Cut-off frequency
B = fir1(N,Fcut/(Fs/2)) % Filter coefficients in length N+1 vector B
t = [0:L-1]*Ts; % time array
A_m = 80; % Amplitude of main component
F_m = 5; % Frequency of main component
P_m = 80; % Phase of main component
y_m = A_m*sin(2*pi*F_m*t - P_m*(pi/180));
A_s = 40; % Amplitude of secondary component
F_s = 40; % Frequency of secondary component
P_s = 20; % Phase of secondary component
y_s = A_s*sin(2*pi*F_s*t - P_s*(pi/180));
y = round(y_m + y_s); % sum of main and secondary components (rounded to integers)
y_filt = round(filter(B,1,y)); % filtered data (rounded to integers)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Serial_port_object = serial(comport); % create Serial port object
set(Serial_port_object,'InputBufferSize',L) % set InputBufferSize to length of data
set(Serial_port_object,'OutputBufferSize',L) % set OutputBufferSize to length of data
fopen(Serial_port_object) % open Com Port
fwrite(Serial_port_object,y,'int8'); % send out data
data = fread(Serial_port_object,L,'int8'); % read back data
fclose(Serial_port_object) % close Com Port
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
subplot(2,1,1)
hold off
plot(t,y)
hold on
plot(t,y_filt,'r')
plot(t,y_filt,'ro')
plot(t,data,'k.')
ylabel('Amplitude')
legend('y','y filt (PC)','y filt (PC)','y filt (muP)')
subplot(2,1,2)
hold off
plot(t,data'-y_filt)
hold on
xlabel('time')
ylabel('muP - PC')
figure(1)
It is also not advised to keep interrupt routines doing long processing routines, because you will impact on interrupt latency. Bytes comming from the PC can get easily lost, because of buffer overrun on the serial port.
The best is to build a FIFO buffer holding a resonable number of input values. The USCI routine fills the FIFO while the main program keeps looking for data inside it and process them as they are available.
This way, while the data is being processed, the USCI can interrupt to handle new incomming bytes.
When the FIFO is empty, you can put the main process in a suitable LPM mode to conserve power (and this is the best MSP430 feature). The USCI routine will wake the CPU up when a data is ready (just put the WAKEUP attribute in the USCI handler if you are using MSPGCC).
In such a scenario be sure to declare volatile every variable that are shared between interrupt routines and the main process.