1 USB to 3 UART

[vikash23]

Hi,



Please see the attached image.



I have three devices with only UART in all three devices



I need to communicate with all three devices at the same time using one USB



I have see USB to UART using FTDI converter . But that is for one to one.



Here one USB to 3 UART I need to connect. Is it possible ?



I saw one FTDI device FT4232H and the datasheet says "Single chip USB to four channels UART (RS232, RS422 or RS485) or Bit-Bang interfaces. "



can I use this device for my application ?



If yes, then how do I interface AD,BD,CD,DD Bus0 to Bus 7 to my device which has got only tx rx, Do I need to any interface IC?



Also I know RS232 is multi drop. Can I use RS232 for this sort of communication ?

 

[KlausST]

Hi,

I have three devices with only UART in all three devices

what signal levels? V_ih, V_il

I need to communicate with all three devices at the same time using one USB

this means you want to send all three devices the same input data.
USB_out = device1_in = device2_in = device3_in?

can I use this device for my application ?

I see a good chance...

If yes, then how do I interface AD,BD,CD,DD Bus0 to Bus 7 to my device which has got only tx rx, Do I need to any interface IC?

What is "AB, BD, CD, DD" what is "Bus0 to Bus7"?

Also I know RS232 is multi drop. Can I use RS232 for this sort of communication ?

RS232 is not multidrop. RS232 tells the voltage levels for UART communication, usually peer to peer.

You may use UART as multi drop bus, but it needs extra hardware (optocouplers) and it needs a dedicated protocol (device adressing)
Only you know whether this requirements can be fulfilled by your devices...

Why not:
Use FT4232.
FTDI_UART1_Tx = device1_Rx = device2_Rx = device3_Rx
Device1_Tx = FTDI_UART1_Rx
Device2_Tx = FTDI_UART2_Rx
Device3_Tx = FTDI_UART3_Rx

Provided all voltage levels are compatible.

Klaus

 

[vikash23]

Hi,
From your recommended method

Use FT4232.
FTDI_UART1_Tx = device1_Rx = device2_Rx = device3_Rx
Device1_Tx = FTDI_UART1_Rx
Device2_Tx = FTDI_UART2_Rx
Device3_Tx = FTDI_UART3_Rx

I have made a pictorial representation. Please have a loknat the attached image.

Also can i please know what about FTDI_UART2_Tx and FTDI_UART3_Tx?

Why not FTDI 1 goes to dev 1 tx rx,
FTDI 2 goes to dev 2 tx rx,
FTDI 3 goes to dev 3 tx rx,

See the second image attached. Can i follow the daisy chain method with one FTDI? Provided all the three devices are awake.

 

[FvM]

Both connection variants require special protocol features implemented in the devices, recognition of device addresses in the first and addressing and forwarding data packets in the second. You are the only one who knows if your devices have the capabilities.

Using a four channel USB bridge like FT4232 won't require any special device features.

As for the driver level, RS232 standard uses high level (+/- 5 to +/-12 V) signals, FT4232 has only logic level (0 to 3.3 or 5V ) signals. You need to check which level is used by your devices. There are however multi-channel USB to RS232 converteron the market, they contain an IC like FT4232 and the level converters.

 

[KlausST]

Hi,

Did you answer a single question?

Also can i please know what about FTDI_UART2_Tx and FTDI_UART3_Tx?

Nothing, = unconnected.

Why not FTDI 1 goes to dev 1 tx rx,
FTDI 2 goes to dev 2 tx rx,
FTDI 3 goes to dev 3 tx rx,

I just followed your requirement: "I need to communicate with all three devices at the same time using one USB ".
And it was you who meantioned three UARTs.
You clearly said "at the same time" This can only be when all device_Rx are connected to one USB_Tx.
With my method all devices get the information at the same time and may respond at the same time.

See the second image attached. Can i follow the daisy chain method with one FTDI? Provided all the three devices are awake.

What does "awake" mean? This is the first time you mentioned it.
You are free to daisy chain the devices, but then they need special "daisy chain" protocol and software. And they are not "at once" but one after the other .
You can do with one FTDI ... you even can do with single FTDI_UART --> FT232 (not FT4232)

Klaus

 

[danadakk]

A single chip approach would look like -

As you can see most of the chips resources still available for use for other tasks as well. Right
hand window, resources used/left.

Onchip DMA used to make life easy handling traffic. Chip has analog resources as well as
traditional PWM, Counters, registers, ARM Core, LUT, Logic (Discrete gates and such), DSP,
display.....

Single chip solution. IDE (PSOC Creator) and Compiler free.



Regards, Dana.