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Raspberry Pi RS232 shield


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#1 chain

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Posted 05 May 2014 - 12:42 AM

I just received the rs232 Shield for the Pi and noted that it uses the MAX232 chip, which is a 5V logic chip. The Pi interface is 3.3V and docs strongly warn about connecting 5V to it's interace pinout. I have verified that your Shield board will apply 5V to the Pi's RXD pin. I am very concerned about using this board - how do you justify the potentially fatal mismatch in logic levels? I don't want to let the magic smoke out of my Pi! Why not use the MAX3232 chip at 3.3V? The board looks very nice, otherwise. Thanks -- Geoff


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#2 Guest_User_*

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Posted 12 May 2014 - 06:02 AM

I just received the rs232 Shield for the Pi and noted that it uses the MAX232 chip, which is a 5V logic chip. The Pi interface is 3.3V and docs strongly warn about connecting 5V to it's interace pinout. I have verified that your Shield board will apply 5V to the Pi's RXD pin. I am very concerned about using this board - how do you justify the potentially fatal mismatch in logic levels? I don't want to let the magic smoke out of my Pi! Why not use the MAX3232 chip at 3.3V? The board looks very nice, otherwise. Thanks -- Geoff

I have measured the same +5vdc voltage for the LinkSprite Baseshield for the GPIO interface, it appears they are reusing designs for their Arduino "kits" and it does not appear they are

testing any of the RPI devices they are building. If they were they would realize they need a voltage shifter to +3.3vdc logic levels. They do not care about anyone but their pocket books.

 

I have emailed back and forth with the engineer/owner Jingfeng Liu and he admitted to having incorrect product documentation and sample coding for the products, however they have not done anything to correct it. Also when emailed asking for clarification of the logic level mismatch they are earily silent like they know they messed something up.



#3 jim

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Posted 13 May 2014 - 03:31 AM

Please refer to: http://learn.linkspr...th-python-code/. The python code has been updated.

 

The linker LED and linker button has 10K resistors. They are good to handle voltage translation. 



#4 Guest_Confused_*

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Posted 26 August 2014 - 06:08 AM

Please refer to: http://learn.linkspr...th-python-code/. The python code has been updated.

 

The linker LED and linker button has 10K resistors. They are good to handle voltage translation. 

So how Jim, when I measure the voltage going into the Pi on the GPIO input pin that that base shield is connected to do I get +4.5 - +5vdc on the gpio input pin, there was a reason after using your

Pi linker kit that I smoked the 1amp power supply to the Pi and it took an hour to power back on after the amp power supply died. Your explanation is not one of customer service or of caring. Are you really Jinfeng?






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