Uart to LVDS MinPci-e (Not rs485)

Projects Networking, Protocols, and Devices
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My understanding so far is PE0_TX-/PE0_RX- is A & PE0_TX+/PE0_RX+ is B for differential pairs of rs485.
So i have PEO_CLK+/PEO_CLK- & not sure about it, a clock for each pair?
Possibly can be omitted?

I see TTL2RS486 devices , A+ / B- with ground, it's a bit confusing, is A plus or minus?

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JB_AU:
My understanding so far is PE0_TX-/PE0_RX- is A & PE0_TX+/PE0_RX+ is B for differential pairs of rs485.
So i have PEO_CLK+/PEO_CLK- & not sure about it, a clock for each pair?
Possibly can be omitted?

I see TTL2RS486 devices , A+ / B- with ground, it's a bit confusing, is A plus or minus?

RS485 is usually connected to a UART, most UARTs are configured to be high +v when idle. This results in A being Positive and B being Negative with respect to each other.

Your PE0_TX-/PE0_RX- may be a 'active state' label.

for RS485 you need to connect A,B,GND. depending on which RS485 IC you use, |A-B| < 5v and (A <5v)&(A>GND), (B<5v)&(B>GND).

Some RS485 IC's can support extend voltage ranges. If you have different GND potentials for safety insert a 100ohm resistor between the IC GND and the Bus GND.

Here is a schematic of a working RS485: (the 100ohm GND connection is off page on the connector page.)

The jumpers are used to:

  • Terminate the bus.
    120ohm for each end.
    2x680ohm for bus polarity, noise reduction
  • The jumper JP3_5,JP3_6 allow collision detection by comparing actual TX with expected TX.
    With this jump open, anything send out will be echoed back into the UART. The RX is at least
    one character behind TX.

Chuck.

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Differential Clock?

4

I looked at MAX308x but its 5v, with full duplex & enable for Rx&Tx.

I want the exact thing in 3.3v though?

And yes, only using half duplex mcu.

My thinking is to use the full duplex ic with the enable transmit, then enable receive, since i know when data is being sent & received and no extra circuitry.

Or did i miss the boat.

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JB_AU:

I am confused. I answered the wrong question.

My previous post was about RS485.

Your questions are about PCI-e interfaces. Totally different.

They are both differential interfaces:
But, RS485 is slew rate limited from 100Kb to 10Mb.
PCI-E uses totally different drivers. Version 1.0 is 2Gb, Version 4.0 is 15Gb.

Chuck.

7

Thankyou Tony from National Semiconductors , i have appropriately changed the subject.

RS485, RS422, RS423, LVDS, MLVDS etc all use similar buses as all are a subset protocol of RS232.

The differential lines of mini pci-e for modems are generally lvds (low voltage differential serial) a technology synonymous with driving tft/lcd, which is why i overlooked it.

The schematic in post 4 is correct, the ic is incorrect, using DS90LV019 3.3V or 5V LVDS Driver/Receiver.

RE&TE HIGH is transmit
RE&TE LOW is receive

The 1K resistors are for false triggering when reprogramming an avr.

Modem driven from 3.7v lipo 20,000+mah (Transmit is 2A)

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