Hi Bill,
I understand what you try to do but it does not work because the hardware
baudrate setting is calculated at compile time not at runtime.
In the library usart_common.jal you find the procedure that calculates the
baudrate settings.
I once changed this code to be dynamic and created the following code but I do
not remember if I ever tested it (it compiled as far as I know ?).
I did not use it because it is a lot of code for only calculating and setting
the baudrate. That's why I suggested the other code.
You could leave out the part which calculates it for synchronous mode and based
on the PIC you are using you could leave out the 8-bit or 16-bit baudrate
generator since your PIC has only one of them. In that case the code size is
much smaller.
You could give it a try and if it works let me know.
Kind regards,
Rob
--
------------------------------------------------------------------------------
-- Title: Calculate and set baudrate dynamically for USART 1
-- Arguments: baudrate
-- Returns: TRUE when succesful, otherwise FALSE
-- Notes: Uses bit-constant 'usart_hw_serial' to determine mode of
operation:
-- * TRUE: Asynchronous communications (default)
-- * FALSE: Synchronous communications
--
------------------------------------------------------------------------------
function _calculate_and_set_baudrate_dynamic(dword in baudrate) return bit is
const max_deviation = 5 -- maximum % deviation of the desired baudrate
var dword usart_calculation, real_baud, usart_div_low, usart_div_sync, clock
var word usart_div
var bit succes = TRUE
clock = dword(target_clock)
if (usart_hw_serial == TRUE) then -- USART in asynchronous mode
if (defined(BAUDCON_BRG16) == TRUE) then -- use 16 bit baudrate register
BAUDCON_BRG16 = TRUE
TXSTA_BRGH = TRUE
usart_calculation = ((5 + ((10 * clock) / (4 * baudrate))) / 10) - 1
usart_div = word(usart_calculation)
real_baud = clock / 4 / ((usart_div & 0xffff) + 1)
if (real_baud > baudrate) then
if (100 * (real_baud - baudrate) / baudrate >= max_deviation) then
-- Asynchronous baudrate deviation is too large
succes = FALSE
end if
else
if (100 * (baudrate - real_baud) / baudrate >= max_deviation) then
-- Asynchronous baudrate deviation is too large
succes = FALSE
end if
end if
SPBRGL = byte(usart_div) -- MSB
SPBRGH = byte(usart_div >> 8) -- LSB
else
-- use classic (8 bit) baudrate register
-- <SPBRG> = ( Fosc / ( 4 * Baudrate ) ) -1
-- first try high baudrate, will generate highest accuarcy
-- to get the right rounding (5 + 10*f(x)) /10
usart_calculation =((5 + ((10 * clock) / (16 * baudrate))) / 10) - 1
usart_div = word(usart_calculation)
-- special case if divider is 0, test if deviation is not too much
if usart_div == 0 then
if (100 * (baudrate - (clock / 16))) / baudrate >= max_deviation
then
-- Asynchronous baudrate is too high
succes = FALSE
end if
end if
-- if divider small enough calculate divider and set high-speed
real_baud = clock / 16 / (usart_div + 1)
if usart_div <= 255 then
if (real_baud > baudrate) then
if (100 * (real_baud - baudrate) / baudrate >= max_deviation)
then
-- Asynchronous baudrate deviation is too large
succes = FALSE
end if
else
if (100 * (baudrate - real_baud) / baudrate >= max_deviation)
then
-- Asynchronous baudrate deviation is too large
succes = FALSE
end if
end if
SPBRGL = byte(usart_div)
TXSTA_BRGH = TRUE
-- try the low-speed mode
else
usart_div_low = ((((10 * clock) / (64 * baudrate)) + 5) / 10) - 1
-- here divider will never be 0
-- but special case to consider,
-- if baudrate is just a little too low
if (usart_div_low > 255) & (100 * ((clock / (64 * 256 )) -
baudrate)) /
baudrate < max_deviation then
SPBRGL = 255
TXSTA_BRGH = FALSE
-- now calculate divider and set high-speed / low-speed bit
elsif usart_div_low <= 255 then
SPBRGL = byte(usart_div_low)
TXSTA_BRGH = FALSE
else
-- Asynchronous baudrate is too low
succes = FALSE
end if
end if
end if
else -- USART in synchronous mode
usart_div_sync = ( clock / ( 4 * baudrate )) - 1
-- special case if divider is 0 or negative
-- test if baudrate is a little bit too high
if usart_div_sync <= 0 then
if (100 * (baudrate - (clock / 4))) / baudrate >= max_deviation then
-- Synchronous baudrate is too high
succes = FALSE
end if
end if
-- special case to consider, if baudrate is just a little too high
if (usart_div_sync > 255) & (100 * ((clock / (4 * 256)) - baudrate)) /
baudrate < max_deviation then
SPBRGL = 255
elsif (usart_div_sync <= 255) then
SPBRGL = byte(usart_div_sync)
else
-- Synchronous baudrate is too low
succes = FALSE
end if
end if
return succes
end function
________________________________
Van: [email protected] <[email protected]> namens Bill Beek
<[email protected]>
Verzonden: dinsdag 18 oktober 2022 11:34
Aan: jallib <[email protected]>
Onderwerp: Re: [jallib] Baudrate control
Hello Rob,
Thank you for your cooperation, yesterday I had already seen the code.
Now let's figure out how I can fit it into my program.
Maybe my question was not entirely clear so I send a piece of the code to show
how I imagined it.
Kind regards, Bill.
MCU = 16F876A 20 MHz The problem here is that var "set" must be a constant.
Short vars for testing only.
var byte c1,c2,c3
var byte set -- Baud indicator
const serial[8]={1200,2400,4800,9600,19200,38400,57600,115200}
;var dword serial[8]={1200,2400,4800,9600,19200,38400,57600,115200}
pin_c1_direction = INPUT
pin_c2_direction = INPUT
pin_c3_direction = INPUT
include serial_hardware
if pin_c1 then
c1 = 1
else
c1 = 0
end if
if pin_c2 then
c2 = 2
else
c2 = 0
end if
if pin_c3 then
c3 = 4
else
c3 = 0
end if
set = c1 + c2 + c3 + 1
const serial_hw_baudrate = serial[set]
;var dword serial_hw_baudrate = serial[set]
serial_hw_init()
On Tuesday, October 18, 2022 at 7:14:34 AM UTC+2 [email protected] wrote:
Hello Bill,
I posted an example but never received it my self so this is a retry.
Kind regards,
Rob
Op maandag 17 oktober 2022 om 19:52:25 UTC+2 schreef [email protected]:
Hi Bill,
I applied the suggestion of Kiste in one of my programs. Here is a part of that
program. This is for a PIC running at 48 MHz target clock.
I had to look up a specific baudrate to see if it was valid. If so I set the
new baudrate.
You see 4 parts (not all needed)
1. Define valid bauddrates. You could skip this
2. Check if a given baudrate is valid. You could skip this too.
3. The baudrate calculation based on the given baudrate + initialize the
USART. You need this. Note: baudrate calculation is of type dword.
4. The intiallization routine of the USART with the calculation. You need
this.
; List of baudrates supported. See page 262 of the datasheet.
; Formula for baudrate calclation for 8 byte asynchronous mode
; with for sync = FALSE and brg16 = TRUE and brgh = FALSE:
; brg = target_clock/(baudrate * 16) - 1
const dword SUPPORTED_BAUDRATES[] = {
110, 300, 600, 1200, 2400, 4800, 9600, 14400,
19200, 28800, 38400, 57600, 115200, 230400
}
; Check if the given baudrate is supported and return TRUE if so.
function supported_baudrate(dword in baudrate) return bit is
var byte index
var bit found = FALSE
for count(SUPPORTED_BAUDRATES) using index loop
if (SUPPORTED_BAUDRATES[index] == baudrate) then
found = TRUE
end if
end loop
return found
end function
baudrate_calculation = (target_clock/(current_baudrate * 16)) - 1
usart_init(word(baudrate_calculation))
; Initialize the USART with the given baudrate value. The USART is enabled.
procedure usart_init(word in baudrate_value) Is
usart_disable()
; Use 16 bit baudrate generator and set baudrate
BAUDCON = 0b0000_1000
SPBRG = baudrate_value
;Initialise transmitter, 8 bits, asynchronous mode, low speed.
TXSTA = 0b0000_0000
; Initialise receiver and serial port, 8 bits
RCSTA = 0b1000_0000
usart_enable()
end procedure
Hope this helps.
Kind regards,
Rob
________________________________
Van: [email protected] <[email protected]> namens Bill Beek
<[email protected]>
Verzonden: maandag 17 oktober 2022 19:40
Aan: jallib <[email protected]>
Onderwerp: Re: [jallib] Baudrate control
Thanks Kiste for your reply. My teacher said more than 50 years ago that poking
in memory was not a good way of programming,
but I did think that this was also a possibility. If this turns out to be the
only possibility,
I'm not sure how to go about it I don't see anything in the documentation
about writing directly in the PIC memory
except that you can use assembler instructions. Unfortunately I am not well
informed about the PIC asm code.
A long time ago I programmed various micro processors.
I would like to hear if you want to share a piece of code what i can alter for
my needs.
Thanks in advance, Bill.
On Monday, October 17, 2022 at 4:47:20 PM UTC+2 Kiste wrote:
Hi Bill,
I've used different baud rates, but I did not modify the serial libraries for
that. I just calculated the register values by hand and poked the different
values to the different registers. The baud rate calculation in the libraries
is not a thing which is good to be done at runtime. For certain baud rates, the
lib will refuse to compile and inform you, that your desired baud rate cannot
be set due to a deviation from the desired value which is to large to reliably
work. That can't be done at runtime for a start.
Greets,
Kiste
Am Montag, 17. Oktober 2022, 15:39:54 MESZ hat Bill Beek <[email protected]>
Folgendes geschrieben:
Hello everyone, Is there anyone who has a solution to my problem. I am working
on a serial LCD now that I have this working, I want to select the baud rate
before running the program. Unfortunately, the "const serial_hw_baudate" do not
easily change. In the library "usart_common" I changed all the constants in a
variable "var dword" but I keep getting error messages from this lib. Maybe I'm
overlooking something, or is there a simple method to set the Baud rate under
software control.
Kind regards, Bill
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