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flasherror
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Joined: 07/01/2019
Location: United States
Posts: 159

Posted: 02:33pm 01 May 2020

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Anyone else using Duinomite Mega boards? (MMBasic v4.5)

I realize Geoff is pretty busy but it's been a while since MMBasic for this board has been updated.
No SELECT CASE
No Cfunctions (please correct me if I'm wrong)
No built-in bit shift functions (faster than writing your own BASIC shift code)
No CRC16

1. Regarding the last point - I'm doing a project where I need to checksum via CRC16 (Modbus).
I know that on fruitoftheshed there is example CRC code, but it seems to be for MMBasic v5. (In any case being Basic it might be slow).
Does anyone have any tested v4.5 code? Is it true that C functions are not supported for Duinomite v4.5?

2. If anyone else is using Duinomite Mega boards, how do you deal with the increasing "outdated" nature of MMBasic? (Before you say use a different board/chip the reason I use DM is that these boards are cheap and feature complete (for example connecting to devices via DB9 serial ports etc, or making use of plug-in UEXT boards to add Wifi (via ESP8266). In short, I can focus on software rather than hardware.
Is there the equivalent of a "standard" feature complete board for other *mites? Or a "base" motherboard that allows I/O expansion?

3. Is there a documented setup for attempting to build custom firmware for Duinomite MMBasic? (what version of compiler/IDE etc so avoid possible problems)

4. Has anyone besides Geoff made any updated Duinomite MMBasic firmware?

Thanks

JohnS
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Joined: 18/11/2011
Location: United Kingdom
Posts: 4044

Posted: 03:19pm 01 May 2020

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Can't help much but I expect the bit shift will be fast enough if you do the obvious and I also expect CRC16 will be fast enough.

John

Turbo46

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Joined: 24/12/2017
Location: Australia
Posts: 1642

Posted: 08:57pm 01 May 2020

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flasherror, the table lookup version of the CRC16 routine is pretty fast see here.

One of my future projects is to make a MODBUS master using the Maximite. I'm sure the CRC16 routine will work well if you remove the references to integers and use the integer divide in place of the shift left instruction.

Now I have dusted off my Maximite I'll see if I can try it later today.

Bill

Keep safe. Live long and prosper.

JohnS
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Posted: 09:20pm 01 May 2020

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Looks like it's on fruitoftheshed already mentioned.

John

Turbo46

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Joined: 24/12/2017
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Posts: 1642

Posted: 01:46am 02 May 2020

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CRC16 works on the Maximite after few changes and a lot of head scratching. I was caught out by the LOCAL declaration, you cannot assign a value to a LOCAL variable when you declare it.

Use it in the same way as the one in the library. I'll put this one in the library soon.

Quote ' Modbus CRC Generation using lookup table for the Maximite
' Test program

DIM crc_table(255)

' Make the CRC table first
CRCTable
'
'********************** TEST ROUTINE **************************
' Test messages
test1$ = CHR$(01)+CHR$(03)+CHR$(04)+CHR$(&H3F)+CHR$(&H80)+CHR$(0)+CHR$(0)
' check1$= CHR$(&HF7)+CHR$(&HCF)
test2$ = CHR$(01)+CHR$(&H10)+CHR$(0)+CHR$(02)+CHR$(0)+CHR$(02)+CHR$(04)+CHR$(&H42)+CHR$(&H70)+CHR$(0)+CHR$(0)
' check2$= CHR$(&H67)+CHR$(&HD5)
test3$ = CHR$(01)+CHR$(03)+CHR$(00)+CHR$(00)+CHR$(00)+CHR$(02)
' check3$= CHR$(&HC4)+CHR$(&H0B)
T = TIMER
PRINT HEX$(CRC16(test1$),4) " " TIMER - T " mS"
T = TIMER
PRINT HEX$(CRC16(test2$),4) " " TIMER - T " mS"
T = TIMER
PRINT HEX$(CRC16(test3$),4) " " TIMER - T " mS"
END
'******************** TEND TEST ROUTINE ************************

' Generates the lookup table
SUB CRCTable
FOR i = 0 TO 255
k = i
FOR j = 1 TO 8
IF k AND 1 THEN
k = k \ 2
k = k XOR &HA001
ELSE
k = k \ 2
ENDIF
NEXT j
crc_table(i)=k
NEXT i
END SUB

' Calculates the Modbus CRC
FUNCTION CRC16(a$)
LOCAL CRC, n
CRC = &HFFFF
FOR n = 1 TO LEN(a$)
CRC = (crc \ 256) XOR crc_table(crc XOR ASC(MID$(a$, n, 1)) AND &HFF)
NEXT n
CRC16 = (CRC MOD 256)*256 + INT(CRC\256) MOD 256
END FUNCTION

The timing results are:

F7CF 5 mS
67D5 7 mS
C40B 4 mS

Geoff did say he was going to update the Maximite to MMBasic 5.x but that was a while ago.

Bill

Keep safe. Live long and prosper.

Volhout
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Joined: 05/03/2018
Location: Netherlands
Posts: 5091

Posted: 03:13pm 02 May 2020

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Hi Bill,

CRC16 = (CRC MOD 256)*256 + INT(CRC\256) MOD 256

The INT may not be needed, since both MOD and integer divide (\) leave an integer.

Volhout

On the F4 the code executes in 2ms per CRC16
Edited 2020-05-03 01:15 by Volhout

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flasherror
Senior Member

Joined: 07/01/2019
Location: United States
Posts: 159

Posted: 03:43pm 02 May 2020

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Turbo46 said CRC16 works on the Maximite after few changes and a lot of head scratching. I was caught out by the LOCAL declaration, you cannot assign a value to a LOCAL variable when you declare it.

Use it in the same way as the one in the library. I'll put this one in the library soon.

Many thanks, Turbo46! Maybe a Tips N' Traps section (for various MMBASIC versions) describing things like that LOCAL "gotcha" would be a good idea. On P34 of the MMBASIC the command reference for LOCAL does not seem to indicate that assignment could be done in the same statement so that looks a bit inconsistent with what one might expect.

Turbo46 said
Geoff did say he was going to update the Maximite to MMBasic 5.x but that was a while ago.

For when he does get around to it, is there a wishlist of improvements put together by the community?

If there is interest I can post my wish list in a new thread so others can add to it and we can have a public idea discussion.

flasherror
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Joined: 07/01/2019
Location: United States
Posts: 159

Posted: 03:50pm 02 May 2020

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Turbo46 said

T = TIMER
PRINT HEX$(CRC16(test1$),4) " " TIMER - T " mS"
T = TIMER
PRINT HEX$(CRC16(test2$),4) " " TIMER - T " mS"
T = TIMER
PRINT HEX$(CRC16(test3$),4) " " TIMER - T " mS"

Just a quick question:
Would it be more accurate for time measurement to do something like:

T1=TIMER
CRC$=HEX$(CRC16(test1$),4)
T2=TIMER
PRINT CRC$; " ";(T2-T1);" mS"

to minimise the overhead of PRINT statement? (excluding it as much as possible from timing measurement?)

Turbo46

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Joined: 24/12/2017
Location: Australia
Posts: 1642

Posted: 10:39pm 02 May 2020

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Volhout said The INT may not be needed, since both MOD and integer divide (\) leave an integer.

I think you are right and I did look at that at one stage while struggling with the LOCAL issue (I was looking for faults everywhere else) but considered it safer to leave it in for now.

flasherror said Maybe a Tips N' Traps section

I think that's a good idea. Maybe a post in this forum could start it and some member(s) could add them to a library or document registry entry? It could be handy when/if MMBasic 5 for the Maximite arrives because I somehow doubt that it will be 100% compatible with 4.5C.

flasherror said is there a wishlist of improvements put together by the community?

There is this link but that is for a future new Maximite.

flasherror said Would it be more accurate for time measurement to do something like:...

Yes, I guess it would technically, but the 1mS resolution is too coarse anyway. I ran the test several times and the results sometimes varied by 1ms, probably setting the timer to 0 first would help too rather than start at some unknown point in the 1mS time step. If you test it say 1000 times and average it out you would get a more accurate measurement if you ignore the overhead of the FOR/NEXT loop.

Bill

Keep safe. Live long and prosper.

Turbo46

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Joined: 24/12/2017
Location: Australia
Posts: 1642

Posted: 07:16am 03 May 2020

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Here is a slightly modified version of the MODBUS CRC16 code for the Maximite. Ive added a LOCAL instruction to the CRCTable subroutine and removed the INT function from the CRC16 function as suggested by Volhout, it is not needed.

Quote ' Modbus CRC Generation using lookup table for the Maximite

DIM crc_table(255)

' Make the CRC table first
CRCTable
'
' Generates the lookup table
SUB CRCTable
LOCAL i, j, k
FOR i = 0 TO 255
k = i
FOR j = 1 TO 8
IF k AND 1 THEN
k = k \ 2
k = k XOR &HA001
ELSE
k = k \ 2
ENDIF
NEXT j
crc_table(i)=k
NEXT i
END SUB

' Calculates the Modbus CRC
FUNCTION CRC16(a$)
LOCAL CRC, n
CRC = &HFFFF
FOR n = 1 TO LEN(a$)
CRC = (crc \ 256) XOR crc_table(crc XOR ASC(MID$(a$, n, 1)) AND &HFF)
NEXT n
CRC16 = (CRC MOD 256)*256 + CRC \ 256 MOD 256
END FUNCTION

Bill

Keep safe. Live long and prosper.

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