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| Posted: 05:18pm 14 Apr 2026 |
My next challenge is to save signed integers to an I2c memory chip. They will only range from say -300 to +900 so will be saving as two bytes (high and low) as if a 16bit integer, not the incoming MMBasic 64bit.
For example -
Dim as integer Xmin,Dhi,Dlo
Xmin=-298
...
...
I2c write &h50,0,4,1,0,Dhi,Dlo
I'm already writing small positive MMBasic 64bit integers as single bytes as MMBasic converts/truncates to 8bit in the i2c command itself.
Wondering what the fastest and most efficient way would be to do this ?
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| Posted: 05:23pm 14 Apr 2026 |
bin2str$ was designed for specifically this
Edited 2026-04-15 03:23 by matherp
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| Posted: 05:37pm 14 Apr 2026 |
I'll have a play sir....
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| Posted: 09:58pm 14 Apr 2026 |
A kind of "hack"
according to C, which relies on the Pico using an ARM with a little-endian format:Dim XminAddr As integer
XminAddr = PEEK(VARADDR Xmin)
Dlo = PEEK(BYTE XminAddr)
Dhi = PEEK(BYTE (XminAddr+1))
XminAddr = PEEK(VARADDR Xmin)
Dlo = PEEK(BYTE XminAddr)
Dhi = PEEK(BYTE (XminAddr+1))
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| Posted: 10:02pm 14 Apr 2026 |
First attempt results in "Error : Argument Count"
a$=Bin2Str$(INT16,xmin,BIG)
I2C2 write &h50,0,4,1,0,a$
Hence writing 4 bytes... '1','0','2byte string' ??
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| Posted: 10:04pm 14 Apr 2026 |
Interesting 😎
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| Posted: 11:33pm 14 Apr 2026 |
When writing a string to a 24Cxx EEPROM the 2 address bytes need to be added to the start of the data.
So perhaps try:-
a$ = Chr$(Mem.addr>>8) + Chr$(Mem.addr And 255) + a$ 'prepend 2 byte memory address to the data
I2C2 WRITE I2C.addr, 0, Len(a$), a$ 'write 2 memory address bytes + up to 32 data bytes
Pause 6 'allow time to write
I2C2 WRITE I2C.addr, 0, Len(a$), a$ 'write 2 memory address bytes + up to 32 data bytes
Pause 6 'allow time to write
Currently you are trying to write a mix of integer bytes and a string which I2C WRITE doesn't accept.
Edited 2026-04-15 11:04 by phil99
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| Posted: 06:07pm 15 Apr 2026 |
Done, created a 4byte string by concatenation of the 2 individual FRAM address bytes (INT8) and the 16bit signed integer data (INT16) into one string for a single I2C2 string write (adding three Bin2Str$ together).
Reading back was much simpler as the I2C read is preceeded by an I2C write that simply sets the FRAM address of the two data bytes that are then I2C read into a string in Str2Bin format.
Don't think there's a more efficient/faster way at the moment unless Peter adds the ability into I2C2write 😎...
Edited 2026-04-16 05:58 by DigitalDreams
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| Posted: 08:37pm 15 Apr 2026 |
I find the
To be a bit offensive
Is it required?
Furthermore, I believe that in the manual, there's a paragraph that suggests the maximum speed is still 400KHz whereas elsewhere, it has been updated to 1000KHz.
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| Posted: 09:35pm 15 Apr 2026 |
Not if you are doing a single write. If writing to more than 1 32 byte page you get a garbled mess if you don't space the writes out.
It doesn't have to be a pause, you could do the writes triggered by a timer or in a tick sub.
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| Posted: 10:16pm 15 Apr 2026 |
I just looked at the datasheet for the Microchip 24LC512 and it says the following:
I assume this behavior is common to many I2C EEPROMs?
This would mean that as long as the write cycle is still ongoing, a read command (to any address, or more precisely, to the LastWriteAddress + 1) will not be acknowledged, and this behavior can be interpreted as "busy"!
This way, a fixed (and unnecessarily long) delay could be avoided.
Regards, bfwolf.
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| Posted: 07:19am 16 Apr 2026 |
Hi bfwolf,
That is the correct way to do it, but in MMbasic that means you will need to poll in a loop until you do not an I2C error anymore. So MMBasic is busy.
So it is not better than a simple "PAUSE 6" (unless a particular fast I2C chip is ready in 4ms).
Regards,
Volhout
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| Posted: 08:42am 16 Apr 2026 |
It appears you can trim some time off, depending on the chip.
> d$ = "ABCDEFGHIJKLMNOPQRSTUVWXYZ012345" '32 bytes
> d$= bin2str$(uint16,48,big)+d$
> i2c2 write &H57,0,len(d$),d$ :t=timer :do :i2c2 read &H57,0,26,d$ :loop until MM.I2C=0 :t= timer-t :?t
2.379
> i2c2 write &H57,0,len(d$),d$ :t=timer :do :i2c2 read &H57,0,26,d$ :loop until MM.I2C=0 :t= timer-t :?t
2.372
>
> d$= bin2str$(uint16,48,big)+d$
> i2c2 write &H57,0,len(d$),d$ :t=timer :do :i2c2 read &H57,0,26,d$ :loop until MM.I2C=0 :t= timer-t :?t
2.379
> i2c2 write &H57,0,len(d$),d$ :t=timer :do :i2c2 read &H57,0,26,d$ :loop until MM.I2C=0 :t= timer-t :?t
2.372
>
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| Posted: 08:57am 16 Apr 2026 |
I just took a quick look at some I2C EEPROM datasheets from various manufacturers (which we have archived on a server at work) and noticed the following:
Many have "WriteCycleTime = max. 5ms", but the AT24C1024, for example, has 10ms — so 6ms might even be too short!
Sure, "PAUSE 6" is the easy way, which probably works 90% of the cases — but it can also sometimes be too short — or usually too long.
By the way, I initially thought "PAUSE 6" would pause for 6 seconds...
@phil99: Good example code shown!
Regards, bfwolf
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| Posted: 01:18am 17 Apr 2026 |
A better speed tester. This one doesn't waste time reading back a lot of bytes, 1 is all that is needed.
Print "Page write speed test for 24C32 EEPROM on I2C2"
Dim Wr$, Re$, tmp$, n%, t, I2C.addr = &H57
Print "Make future failure to write visible."
tmp$ = "Fail"
For n%= 0 To 95 Step 4
Wr$ = Chr$(0)+Chr$(n%)+tmp$
I2C2 write I2C.addr, 0, Len(Wr$), Wr$
Pause 9
Next
Print "Verify data was written"
I2C2 write I2C.addr, 0, 2, 0, 0 : I2C2 read I2C.addr, 0, 96, Re$
Print Re$ : Print
Wr$ = "" : tmp$ = "" : Re$ = ""
For n% = 32 To 127 'make 3 pages of data
Inc Wr$, Chr$(n%)
Next
Print "Test Data"
Print Wr$ : Print
For n% = 0 To 64 Step 32
tmp$ = Mid$(Wr$,n%+1,32)
Print tmp$
tmp$ = Chr$(0) + Chr$(n%) + tmp$
I2C2 write I2C.addr, 0, Len(tmp$), tmp$
t=Timer:Do :I2C2 read I2C.addr,0,1,Re$:Loop Until MM.I2C<>1:t=Timer-t
Print "Time to Write a Page = ";t;"mS" : Print
Next
Print
Re$ = ""
Print " Check saved data for errors."
I2C2 write I2C.addr, 0, 2, 0, 0 : I2C2 read I2C.addr, 0, 96, Re$
Print Re$
If Re$ = Wr$ then Print " Data validated" else Print " Validation failed!"
End
Dim Wr$, Re$, tmp$, n%, t, I2C.addr = &H57
Print "Make future failure to write visible."
tmp$ = "Fail"
For n%= 0 To 95 Step 4
Wr$ = Chr$(0)+Chr$(n%)+tmp$
I2C2 write I2C.addr, 0, Len(Wr$), Wr$
Pause 9
Next
Print "Verify data was written"
I2C2 write I2C.addr, 0, 2, 0, 0 : I2C2 read I2C.addr, 0, 96, Re$
Print Re$ : Print
Wr$ = "" : tmp$ = "" : Re$ = ""
For n% = 32 To 127 'make 3 pages of data
Inc Wr$, Chr$(n%)
Next
Print "Test Data"
Print Wr$ : Print
For n% = 0 To 64 Step 32
tmp$ = Mid$(Wr$,n%+1,32)
Print tmp$
tmp$ = Chr$(0) + Chr$(n%) + tmp$
I2C2 write I2C.addr, 0, Len(tmp$), tmp$
t=Timer:Do :I2C2 read I2C.addr,0,1,Re$:Loop Until MM.I2C<>1:t=Timer-t
Print "Time to Write a Page = ";t;"mS" : Print
Next
Re$ = ""
Print " Check saved data for errors."
I2C2 write I2C.addr, 0, 2, 0, 0 : I2C2 read I2C.addr, 0, 96, Re$
Print Re$
If Re$ = Wr$ then Print " Data validated" else Print " Validation failed!"
End
A:> RUN
Page write speed test for 24C32 EEPROM on I2C2
Make future failure to write visible.
Verify data was written
FailFailFailFailFailFailFailFailFailFailFailFailFailFailFailFailFailFailFailFailFailFailFailFail
Test Data
!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
!"#$%&'()*+,-./0123456789:;<=>?
Time to Write a Page = 1.806000002mS
@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_
Time to Write a Page = 1.787999999mS
`abcdefghijklmnopqrstuvwxyz{|}~
Time to Write a Page = 1.789999999mS
Check saved data for errors.
!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
Data validated
A:>
Page write speed test for 24C32 EEPROM on I2C2
Make future failure to write visible.
Verify data was written
FailFailFailFailFailFailFailFailFailFailFailFailFailFailFailFailFailFailFailFailFailFailFailFail
Test Data
!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
!"#$%&'()*+,-./0123456789:;<=>?
Time to Write a Page = 1.806000002mS
@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_
Time to Write a Page = 1.787999999mS
`abcdefghijklmnopqrstuvwxyz{|}~
Time to Write a Page = 1.789999999mS
Check saved data for errors.
!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
Data validated
A:>
So for this chip a 2mS pause is enough.
Edited 2026-04-17 13:56 by phil99
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| Posted: 07:38am 17 Apr 2026 |
You can't go shorter than what it says on the spec sheet for the chip. That's the timing that the manufacturers know will work. Some chips might be faster on test but one from the next batch might be only just within the spec figure.
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| Posted: 07:52am 17 Apr 2026 |
This line, instead of a Pause...
Do :I2C2 read I2C.addr,0,1,Re$:Loop Until MM.I2C<>1
will let the chip take as much time as it needs but no more.Footnote added 2026-04-17 18:44 by phil99
In view of Peters comment below perhaps this could be used instead.
t=timer :Do :I2C2 read I2C.addr,0,1,Re$:Loop Until MM.I2C<>1 Or timer-t >6
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| Posted: 08:29am 17 Apr 2026 |
This is a bad idea. This could wait for the default I2C timer to expire (1 second) before returning depending on what the device does with the early request.
If you have a device that needs a 5mSec wait then you need to wait 5mSec. The way to do this without blocking would be a settick callback timer
Edited 2026-04-17 18:32 by matherp
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| Posted: 11:32am 17 Apr 2026 |
Good point, added a 5mS timeout to the loop and a counter to record the number of times the timeout is reached.
Then made it loop continuously to see how often this happens.
Print "Page write speed test for 24C32 EEPROM on I2C2"
Dim Wr$, Re$, tmp$, n%, t, LC%, LT, TOut%, I2C.addr = &H57
For n% = 32 To 127 'make 3 pages of data
Inc Wr$, Chr$(n%)
Next
Print "Test Data"
Print Wr$ : Print
Do
For n% = 0 To 64 Step 32
tmp$ = Mid$(Wr$,n%+1,32)
Print tmp$
tmp$ = Chr$(0) + Chr$(n%) + tmp$
I2C2 write I2C.addr, 0, Len(tmp$), tmp$
t=Timer:Do :I2C2 read I2C.addr,0,1,Re$:Loop Until MM.I2C<>1 Or Timer-t>5:t=Timer-t
Print "Time to Write a Page = ";t;"mS"
If t>5 Then
Print "*********** 5mS Timout Exceeded ************"
Inc TOut%
EndIf
Next
Print
Re$ = ""
Print " Check saved data for errors."
I2C2 write I2C.addr, 0, 2, 0, 0 : I2C2 read I2C.addr, 0, 96, Re$
Print Re$ ': Print
If Re$ = Wr$ Then Print " Data validated" Else Print " Validation failed!"
If t > LT Then LT = t
Inc LC%
Print "Loop Count =";LC%, "Max. Write Time =";LT, "Number of Timeouts =";TOut%
Print "Start again" : Print : Print
Loop
End
Dim Wr$, Re$, tmp$, n%, t, LC%, LT, TOut%, I2C.addr = &H57
For n% = 32 To 127 'make 3 pages of data
Inc Wr$, Chr$(n%)
Next
Print "Test Data"
Print Wr$ : Print
Do
For n% = 0 To 64 Step 32
tmp$ = Mid$(Wr$,n%+1,32)
Print tmp$
tmp$ = Chr$(0) + Chr$(n%) + tmp$
I2C2 write I2C.addr, 0, Len(tmp$), tmp$
t=Timer:Do :I2C2 read I2C.addr,0,1,Re$:Loop Until MM.I2C<>1 Or Timer-t>5:t=Timer-t
Print "Time to Write a Page = ";t;"mS"
If t>5 Then
Print "*********** 5mS Timout Exceeded ************"
Inc TOut%
EndIf
Next
Re$ = ""
Print " Check saved data for errors."
I2C2 write I2C.addr, 0, 2, 0, 0 : I2C2 read I2C.addr, 0, 96, Re$
Print Re$ ': Print
If Re$ = Wr$ Then Print " Data validated" Else Print " Validation failed!"
If t > LT Then LT = t
Inc LC%
Print "Loop Count =";LC%, "Max. Write Time =";LT, "Number of Timeouts =";TOut%
Print "Start again" : Print : Print
Loop
End
!"#$%&'()*+,-./0123456789:;<=>?
Time to Write a Page = 1.767999999mS
@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_
Time to Write a Page = 1.83mS
`abcdefghijklmnopqrstuvwxyz{|}~
Time to Write a Page = 1.825999999mS
Check saved data for errors.
!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
Data validated
Loop count = 7574 Max. Write Time = 1.833000001 Number of Timeouts = 0
Start again
!"#$%&'()*+,-./0123456789:;<=>?
Time to Write a Page = 1.824999999mS
@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_
Time to Write a Page = 1.821mS
`abcdefghijklmnopqrstuvwxyz{|}~
Time to Write a Page = 1.823000001mS
Check saved data for errors.
!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
Data validated
Loop count = 7575 Max. Write Time = 1.833000001 Number of Timeouts = 0
Start again
Time to Write a Page = 1.767999999mS
@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_
Time to Write a Page = 1.83mS
`abcdefghijklmnopqrstuvwxyz{|}~
Time to Write a Page = 1.825999999mS
Check saved data for errors.
!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
Data validated
Loop count = 7574 Max. Write Time = 1.833000001 Number of Timeouts = 0
Start again
!"#$%&'()*+,-./0123456789:;<=>?
Time to Write a Page = 1.824999999mS
@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_
Time to Write a Page = 1.821mS
`abcdefghijklmnopqrstuvwxyz{|}~
Time to Write a Page = 1.823000001mS
Check saved data for errors.
!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
Data validated
Loop count = 7575 Max. Write Time = 1.833000001 Number of Timeouts = 0
Start again
Edit.
A longer run.
Check saved data for errors.
!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
Data validated
Loop count = 84732 Max. Write Time = 1.833000001 Number of Timeouts = 0
Start again
!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
Data validated
Loop count = 84732 Max. Write Time = 1.833000001 Number of Timeouts = 0
Start again
Edited 2026-04-17 22:07 by phil99
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Location: United KingdomPosts: 65
| Posted: 12:22pm 01 May 2026 |
Hi Peter
Worked well in that case yet I face a new challenge. Reading temperature and pressure data in 24-bit signed format. Three consecutive bytes (or 6 consevutive bytes for both). Bin2str$ and it's counterpart have no 24-bit options. It seems I have to do this conversion manually....