UART/CODE problem Oshonsoft

[camerart]

Hi,
When setting the BAUD rate on a PIC, one of the settings is BRGH, the H stans for High.
what I want to know is, what is high and what is low?
In other words when is BRGH used?
Camerart

 

[DogFlu66]

Using the assembler editor you can make the task easier, because it tells you the records and the error percentage. If memory serves, I think that up to a 2% error rate is acceptable but it is recommended that it be <=1%.

; Compiled with: OshonSoft PIC18 Basic Compiler v4.61
; Microcontroller model: PIC18F46K22
; Clock frequency: 64.0MHz
;
ORG 0x000000
BSF RCON,IPEN
GOTO L0002
ORG 0x000008
RETFIE
ORG 0x000018
RETFIE
; User code start
L0002:
; 1: Define CLOCK_FREQUENCY = 64
; The value of 'CLOCK_FREQUENCY' is 64
; 2: Hseropen 9600
; exact baud rate achieved = 9598.08038; bit period = 104.1875µs; baud rate error = 0.01%
BSF TRISC,6
BSF TRISC,7
MOVLW 0x82
MOVWF SPBRG1
MOVLW 0x06
MOVWF SPBRGH1
CLRF BAUDCON1
BSF BAUDCON1,BRG16
MOVLW 0x24
MOVWF TXSTA1
MOVLW 0x90
MOVWF RCSTA1
; 3: End
L0003 BRA L0003
; Library code
L0001:
RETURN
; End of user code
L0004 BRA L0004
;
;
;
;
;
;
; End of listing
END

 

[camerart]

Using the assembler editor you can make the task easier, because it tells you the records and the error percentage. If memory serves, I think that up to a 2% error rate is acceptable but it is recommended that it be <=1%.

; Compiled with: OshonSoft PIC18 Basic Compiler v4.61
; Microcontroller model: PIC18F46K22
; Clock frequency: 64.0MHz
;
ORG 0x000000
BSF RCON,IPEN
GOTO L0002
ORG 0x000008
RETFIE
ORG 0x000018
RETFIE
; User code start
L0002:
; 1: Define CLOCK_FREQUENCY = 64
; The value of 'CLOCK_FREQUENCY' is 64
; 2: Hseropen 9600
; exact baud rate achieved = 9598.08038; bit period = 104.1875µs; baud rate error = 0.01%
BSF TRISC,6
BSF TRISC,7
MOVLW 0x82
MOVWF SPBRG1
MOVLW 0x06
MOVWF SPBRGH1
CLRF BAUDCON1
BSF BAUDCON1,BRG16
MOVLW 0x24
MOVWF TXSTA1
MOVLW 0x90
MOVWF RCSTA1
; 3: End
L0003 BRA L0003
; Library code
L0001:
RETURN
; End of user code
L0004 BRA L0004
;
;
;
;
;
;
; End of listing
END

Hi D,
I wish I understood ASM, but I don't. My friend who helps me however does, and I'll send this to him, thanks.

I also have Crystals, that make the accuracy almost 0%.

Comments on this and other forums, suggest, that it isn't the timing that's the problem, which makes it a bit difficult.

At the moment we are shortening and re-checking the INTERRUPTS to make them as short as poss, while also getting the the bottom of this problem.

Thanks, and hope for the solution soon.
C

 

[DogFlu66]

I use a ringbuffer that works super well. I have been using the same version but in C for years in my projects and it does not fail.

Ring buffer for serial port (Oshonsoft Basic).

On this occasion I leave a buffer for serial port, it is of the ring buffer type. Video: 'Tests with ring buffer and time bases. 'By COS, 02/2023, OshonSoft Pic Basic IDE v8.38 '************************************************************* Define CONFIG = 0x2f70 Define CONFIG2 = 0x3ffc Define...

www.electro-tech-online.com

 

[DogFlu66]

In all programs I use interruptions every 1mSec. to distribute the time of the functions, along with the serial ringbuffer and to date it works perfectly in both oshonsoft and C.

 

[Ian Rogers]

Hi C.. Remember waaayy back. I wrote a circular buffer for Oshonsoft. I think I gave you a copy.

 

[DogFlu66]

Now I don't remember, I'll look it up and check to see if it's simpler than the one I use.

 

[tumbleweed]

I also have Crystals, that make the accuracy almost 0%.

... and you still have problems so we can FINALLY put this nonsense to bed about baud rate accuracy that has totally side-tracked you from looking for the real isssue.

At the moment we are shortening and re-checking the INTERRUPTS to make them as short as poss

If you have a lot of code in your ISR that could be an issue. Many people make the mistake of trying to process the uart data inside the ISR instead of using the interrupt for what it should be, which is to gather up the incoming bytes into a buffer.

At 38400 baud you have roughly 250us between bytes. An easy way to check this is to set a pin high on entry to the ISR and set it low right before returning. Watch the pin with a scope/logic analyser to see how long your ISR is taking.

 

[camerart]

Hi C.. Remember waaayy back. I wrote a circular buffer for Oshonsoft. I think I gave you a copy.

... and you still have problems so we can FINALLY put this nonsense to bed about baud rate accuracy that has totally side-tracked you from looking for the real isssue.


If you have a lot of code in your ISR that could be an issue. Many people make the mistake of trying to process the uart data inside the ISR instead of using the interrupt for what it should be, which is to gather up the incoming bytes into a buffer.

At 38400 baud you have roughly 250us between bytes. An easy way to check this is to set a pin high on entry to the ISR and set it low right before returning. Watch the pin with a scope/logic analyser to see how long your ISR is taking.

Hi T,
Thanks, I think you have explained this recently, I haven't forgotten.
C

 

[camerart]

Hi C.. Remember waaayy back. I wrote a circular buffer for Oshonsoft. I think I gave you a copy.

Hi R and D,
I remember the ring buffer, and as mentioned. My mate is the skilled one, and I think he has the CODE set up to read each CHAR and put them individually into register memories, but I'll mention ring buffers to him, and see what he thinks.
Cheers, C

 

[tumbleweed]

You don't have to use ring buffers, it just usually makes the code easier.
As long as your mate is processing the chars in < 250us you shouldn't have much of a problem from that side of things.

 

[camerart]

You don't have to use ring buffers, it just usually makes the code easier.
As long as your mate is processing the chars in < 250us you shouldn't have much of a problem from that side of things.

Hi T,
I sent the link to #41, and the folowing posts, which he's read.

We'll meet on Saturday, and go over 'ring buffers', shortening the INTERRUPTS, pointers etc.

I'll ask about the timing/speed.
Thanks, c.

 

[tumbleweed]

You don't have to use ring buffers, it just usually makes the code easier.

I should probably clarify this...

You don't have to use ring buffers, it just usually makes the code timing easier.

Adding circular buffers won't usually make the coding itself easier, it's just that if all the ISR has to do is add chars to the buffer with no/little processing then the ISR is simpler and faster. You still have to deal with processing things outside the ISR in your main program, which can actually make it a bit more complicated.

 

[camerart]

I should probably clarify this...


Adding circular buffers won't usually make the coding itself easier, it's just that if all the ISR has to do is add chars to the buffer with no/little processing then the ISR is simpler and faster. You still have to deal with processing things outside the ISR in your main program, which can actually make it a bit more complicated.

Hi T,
I spoke to my mate this morning, and he understands, what you say. There is another thing to watch, that is loss of GPS signal, which will need extra CODE, but it's all in hand. Previously, there were 'guards' for loss of signal, but he says these add extra time.
C.

 

[rjenkinsgb]

Question:
If you are relying on someone else to do much of the programming anyway - why does the language matter???

If you had used C, far more people could help, using fully proven code, and the project could have been working long ago?

 

[camerart]

Question:
If you are relying on someone else to do much of the programming anyway - why does the language matter???

If you had used C, far more people could help, using fully proven code, and the project could have been working long ago?

Hi R,
This project is eons long, and I didn't ever think it would be so long, complicated, and includes 4x different programs, and a set of peripherals, that have to be coordinated and all working. Each of the peripherals has been an adventure in themselves, and again very challenging.

You will have to accept that I am incapable of learning another language, and am still limited with BASIC, after 40years, it's either BASIC, or I stop. I would really like to use C++, no chance! Be happy you can. I have been lucky enough to be able to carry on in my own terms, and over the years this question has popped up occassionally.

Again, thanks to all that have helped me.
C.

 

[Nigel Goodwin]

I would really like to use C++, no chance!

Not a chance on an 18F PIC - C only.

 

[danadak]

Does not IAR offer C++ on 18F PIC ?

https://guppy.mpe.nus.edu.sg/me3/IARpic18CRefGuide.pdf

And these folks - http://www.sourceboost.com/Products/BoostCpp/SupportedDevices.html


Regards, Dana.

 

[camerart]

Not a chance on an 18F PIC - C only.

Hi N and D,
When I said "not a chance" I meant that there is no chance that I could learn C.
C.

 

[Nigel Goodwin]

Hi N and D,
When I said "not a chance" I meant that there is no chance that I could learn C.
C.

Never say never, I did after MANY years, and numerous failed attempts.

 

[danadak]

@camerart

This is an aside on block based / visual programming.

There are a number of block programmers developed for folks that learn in visual fashion.
MIT with its Scratch, mBlock, Snap4arduino, Flowcode, Nodered, Visuino, Tuniot.....

Here is an example of what a simple voltage to pulse width converter looks like (just 5 blocks) :

You take blocks out of second window, place them in design area (3'rd window),
configure them, and then hit the connect button and mBlock generates C/C++
code and then uses the Arduino IDE programmer to program the target board/part.
The rightmost window is Arduino C/C++ code that mBlock generates from your block
configuration.

I am not advocating this as a way to learn C, rather an adjunct to easily program
simple designs and be able to look at what C/C++ code looks like. Its not optimal
code by any stretch but for simple one off projects fast to get something going.
Some examples :

Pulse Sequence Generator / Smart Timer

Often users, developers, hobbyists need timed and qualified event generators, many resorting to 555 timers and the like. The venerable 555 has had a long run but its limited in accuracy and capability. This approach uses block language to create...

www.electro-tech-online.com

GUI Codeless Processor Design

Micro design has for years relied on ASM and C programming and other languages. Often many tasks are fairly simply but these tools were focused and quite a learning curve, especially ASM and C and C++. There are a number of new GUI based tools that essentially take out the "strong typing"...

www.edaboard.com

Verizon Hotspot Remote Control

Had a problem where I need low cost Network, internet access, at a remote site. Choose to work with Verizon 8800L as it got good reviews for normal attended usage. Motivation was Cell internet only added < $ 20 to the monthly bill. Problems ...

www.electro-tech-online.com

Flow code is done with a flowchart like interface (multiple ways, mix and match) :

A number of folks experimenting with ChatGPT and other AI programs to generate code. Its a
new world in which complex ideas are getting whittled down into simple code methods. C/C++
was/is a strongly typed language, meaning its exact at how you enter and code with it, not forgiving,
"do it my way or die" type language. These new languages are born out of that and making simple
designs a lot easier. Talking voltmeter above link great example of a complex design reduced to
simple block approach.

C/C++, Python, still the "professional" methods, but block and AI catching up rapidly.

Have some fun, try it out on the simple stuff.


Regards, Dana.