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Forum Index : Microcontroller and PC projects : MMBasic bit operator's.... and two's compliment
| Author | Message | ||||
| DigitalDreams Newbie  Joined: 03/05/2025 Location: United KingdomPosts: 34 |
Trying to invert an 8-bit binary number and display the result. Dim as integer a A=57 Print bin$(a,8) Working as expected.... Now add A=inv(a) Print bin$(a,8) Works as expected (inverting all bits) YET Displays ALL 64 bits not the low 8 !?!? On the subject, do we have any commands to handle (convert, display) 8-bit two's compliment binary numbers or do we have to manually manipulate ?. Yes I'm trying to read and write two's compliment binary numbers on the i2c bus. Edited 2025-07-23 00:55 by DigitalDreams |
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twofingers Guru  Joined: 02/06/2014 Location: GermanyPosts: 1662 |
do you mean something like that? a=INV(57) And 2^8-1 Regards Michael causality ≠ correlation ≠ coincidence |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10554 |
BIN2STR$ |
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| PhenixRising Guru Joined: 07/11/2023 Location: United KingdomPosts: 1600 |
 I love these functions  Edited 2025-07-23 02:45 by PhenixRising |
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| DigitalDreams Newbie Joined: 03/05/2025 Location: United KingdomPosts: 34 |
Not entirely useful. I take it the i2c commands strip higher bits from 64 bit integers and only deal with the low 8 ? |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 8262 |
Very likely. AFAIK the I2C system in MMBasic is strictly byte-orientated. If you wanted to send anything longer you would have to split into bytes first. You could send four elements of an array to send a 64-bit integer that way. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10554 |
BIN2STR$ and STR2BIN are specifically designed for things like I2C communication Suppose you want to send a 16-bit signed integer to a I2C device a$=bin2str$(int16,myint) i2c send addr%,0,2,a$ If it wants the bytes the other way round a$=bin2str$(int16,myint,BIG) i2c send addr%,0,2,a$ Same when receiving from i2c - just use str2bin I wrote these functions specifically to make I2C comms to all sorts of devices easy. |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 8262 |
Ah, so the I2C data is still sent as bytes, but as string characters rather than as elements of a single-dimensional array. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| DigitalDreams Newbie Joined: 03/05/2025 Location: United KingdomPosts: 34 |
Ah, I see !. Thanks for clarifying Peter.... |
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