I want to solder the terminal resistor on the recomputer R1000 board so the RS485 can function perfectly. I don't know where to solder the 120ohm terminal resistor.

Products & Technology Raspberry Pi
#1

IMG-20240821-WA0004
IMG-20240821-WA00041920×1080 141 KB

#2

Hello,
You need to go and solder the 120Ω resistor in the position shown in the picture.

企业微信截图_17242939091478(1)
企业微信截图_17242939091478(1)1154×874 143 KB

企业微信截图_17243132232157
企业微信截图_172431322321571528×985 94.5 KB

#3

good job buddy! you made it over here i think you are trying to communicate way too fast

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#4

do you know why they would leave this resistor out? i am not seeing the reason

#5

Hi there,
it’s based on the resistance, type of signalling, P2P or MultiPoint, or MultiDrop.
2-wire half duplex or 4Wire FDX. RS-485 is the most versatile interface of them all.
It was the first balanced driver , long run interface from back in the day. Supports a Master/Slave or Multiple slaves in a multiDrop configuration.

HTH
GL :slight_smile: PJ
:v:

It’s not unusual to have extra resistors along for changing the levels or match longer runs, or multi drop.
RS-232C and RS-485, or even RS-422 weret he standards back in the Day. :+1:

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#6

In simple terms, when communicating via RS485, there needs to be a pull-up resistor, and this pull-up resistor should be either on the sensor end or the device end. To allow sensors with built-in pull-up resistors to work normally on the R1000, we have defaulted to not including the pull-up resistor, but have provided solder pads for users to add one if needed.

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#7

thanks very good answer!

1 Like