Which serial adaptors?

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GCC Observatory

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Jun 20, 2019, 1:46:09 PM6/20/19
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Hey all,

Noob question here... I decided to try my luck at building some one-wire temperature sensors.  I had some spare serial adapters laying around and naively thought I could use them with digitemp, but I'm realizing that not all serial adapters are created equally.

Can anyone tell me which serial adapters work with digitemp?  I see DS9097 and DS9097U and DS2490.  Are there any others?

Thanks

kastrolis

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Jun 20, 2019, 2:55:16 PM6/20/19
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Hi,
Which adapters you have?
Almost any PL2303 will work as DS9097 if you connect Rx with Tx.

k.
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GCC Observatory

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Jun 20, 2019, 7:06:32 PM6/20/19
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Hi,

Thanks for the information - the usb-to-serial adapters I have are all Prolific with the PL2303 chip ... can you explain to me how to "connect Rx with Tx"

I found the following page that describes it in some detail, but it would seem that I have to hack my adapter to make it work.  Is this the right path to take?




On Thursday, June 20, 2019 at 2:55:16 PM UTC-4, kastrolis wrote:
Hi,
Which adapters you have?
Almost any PL2303 will work as DS9097 if you connect Rx with Tx.

k.

On 20.06.19 20:46, GCC Observatory wrote:
> Hey all,
>
> Noob question here... I decided to try my luck at building some one-wire
> temperature sensors.  I had some spare serial adapters laying around and
> naively thought I could use them with digitemp, but I'm realizing that
> not all serial adapters are created equally.
>
> Can anyone tell me which serial adapters work with digitemp?  I see
> DS9097 and DS9097U and DS2490.  Are there any others?
>
> Thanks
>
> --
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kastrolis

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Jun 20, 2019, 7:25:07 PM6/20/19
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Simply sold them together and connect to 1-wire bus.
Then you must be able to read DS18B20 sensors with digitemp:
digitemp_DS9097 -i -s /dev/ttyUSB1 ; digitemp_DS9097 -q -a -n 3
k.
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GCC Observatory

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Jun 20, 2019, 11:39:24 PM6/20/19
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After many attempts at this I'm not getting a sensor reading.  Do you mean to solder the tx and rx together on the usb side or on the serial side?

kastrolis

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Jun 21, 2019, 5:03:32 AM6/21/19
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Serial side. USB have D+ and D-.
What is PCB and prolific chip model?
Your OS?
Is virtual serial port created by OS?
k.
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rct

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Jun 21, 2019, 11:04:37 AM6/21/19
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My reply yesterday didn't seem to go through.

I haven't looked into this in a while, but FTDI based USB serial adapters were generally the most reliable.  I've been using FTDI adapters, DS9097Us with digitemp for at least 15 years. The FTDI adapters I've used have provided stable enough power for a 1-wire bus that's probably 100+ ft long with 10-12 DS18*20s and some oft the combined temp/humidity devices.

Alternatively, if you want a turnkey solution, iButtonLink may still be selling their FTDI based 1-wire interface.  The iButtonLink can work in DS9097U mode with digitemp.


GCC Observatory

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Jun 21, 2019, 12:54:07 PM6/21/19
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The converters I have use the older Prolific chip - the PL-2303HXA/XA chipset.  I do have access to converter that uses the PL-2303HXD chipset from Pluggable, but I'm reluctant to tear that one apart because I'm using it for something else.

My OS is linux Ubuntu 18.04LTS and no this is a not a virtual serial port.


On Friday, June 21, 2019 at 5:03:32 AM UTC-4, kastrolis wrote:

GCC Observatory

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Jun 21, 2019, 12:54:36 PM6/21/19
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Thanks for the info - I'll check out the FTDI adaptors.

GCC Observatory

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Jun 21, 2019, 6:47:08 PM6/21/19
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I think I've done everything correctly... I've soldered pin 2 and 3 on the serial side together and connected it to to the 1-wire bus.  Then I connected pin 5 on the serial side to the ground on the DS18S20.  Am I missing anything?


On Friday, June 21, 2019 at 5:03:32 AM UTC-4, kastrolis wrote:

GCC Observatory

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Jun 21, 2019, 9:47:30 PM6/21/19
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Nope, still no reading from the DS18S20... I must be doing something boneheaded, but I don't know what.

kastrolis

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Jun 22, 2019, 4:17:15 AM6/22/19
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I think I know the problem.
My advices was actually for USB/UART adapter which have inverted and
3.3V signal output directly from PL2303. Now I see that your case is
adapter with 12V and non inverted outputs.
So you need a little bit soldering:
https://www.instructables.com/id/1-wire-communication-interface/
k.
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GCC Observatory

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Jun 22, 2019, 3:35:35 PM6/22/19
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No I'm using prolific USB to uart. I just don't know what I'm doing wrong. Any details you could provide to help with the proper connections would be greatly appreciated.

kastrolis

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Jun 22, 2019, 5:19:21 PM6/22/19
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Hmm...
If it is uart then where you get DB9 pin numbers?
Here is typical PL2303HxA usb/uart adapter:
https://www.ebay.com/itm/192949301788
k.

GCC Observatory

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Jun 22, 2019, 11:11:32 PM6/22/19
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No, this is what I'm using:


I've jumped RX (serial pin 2) and TX (serial pin 3) and attached that to DS18S20 pins 1&3 and then attached GRD (serial pin 5) to the 1-wire bus (DS18S20 pin 2).

Every time I run digitemp with "sudo digitemp_DS9097 -i -s /dev/ttyUSB1"  with that setup I get the following:

DigiTemp v3.7.1 Copyright 1996-2015 by Brian C. Lane
GNU General Public License v2.0 - http://www.digitemp.com
Turning off all DS2409 Couplers

Searching the 1-Wire LAN

It searches for about 5 seconds then returns a command line prompt.

On the other hand, when I reverse the connections to the DS18S20 I get the same thing, but it never returns a command line prompt - it just hangs on "Searching for 1-Wire LAN"

That's about the best detail I can give you as to what I'm doing....

kastrolis

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Jun 23, 2019, 5:17:54 AM6/23/19
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I have never tested but I think this type of adapters will not work
without additional circuit.
k.

On 23.06.19 06:11, GCC Observatory wrote:
> No, this is what I'm using:
>
> https://plugable.com/products/pl2303-db9/
>
> I've jumped RX (serial pin 2) and TX (serial pin 3) and attached that to
> DS18S20 pins 1&3 and then attached GRD (serial pin 5) to the 1-wire bus
> (DS18S20 pin 2).
>
> Every time I run digitemp with "sudo digitemp_DS9097 -i -s
> /dev/ttyUSB1"  with that setup I get the following:
>
> /DigiTemp v3.7.1 Copyright 1996-2015 by Brian C. Lane
> /
> /GNU General Public License v2.0 - http://www.digitemp.com/
> /Turning off all DS2409 Couplers/
> /
> /
> /Searching the 1-Wire LAN/
> /
> /
> It searches for about 5 seconds then returns a command line prompt.
> /
> /
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rct

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Jun 25, 2019, 11:01:29 AM6/25/19
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Serial is probably too overloaded a term in this context without clarifications.

The USB<->DB 9 serial adapter you point to is for RS-232 type devices which use a relatively large voltage range that goes from negative to positive at least -5vdc to +5vdc, originally was closer to -12 vdc to +12 vdc.

If you tried to connect the RX/TX from an RS-232 port to a DS18S20 without building something like a DS9097U to create a 0-5vdc 1-wire bus, it won't work and it is possible your DS18S20 was damaged.

The original DS9097* type devices converted from an RS-232 port down to a 5 vdc 1-wire bus. I think most have a 5 volt regulator in them.

There are simplified 1-wire bus adapters that connect to serial signaling that is at 0-5 vdc levels.  These are for when you are using the output directly off the FTDI 232 or PL2303 or RPi or other system on a chip (SoC) pins that haven't gone through an RS-232 converter.

The USB<->DB 9 serial adapter you are using has essentially two main components in it, a PL2303 USB<->Serial and an RS-232 convert, something like a max232 chip.

If you ware building your own adapter, you want something like an FTDI or PL2303 "breakout" that doesn't have the converter.  These are sold for microcontroller type projects for Arduino, RPi, serial consoles on embedded devices like wireless access points/routers, etc.

Hope this helps,
--Rob

Brian C. Lane

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Jul 1, 2019, 7:44:52 PM7/1/19
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On Tue, Jun 25, 2019 at 08:01:29AM -0700, rct wrote:
> Serial is probably too overloaded a term in this context without
> clarifications.
>
> The USB<->DB 9 serial adapter you point to is for RS-232 type devices which
> use a relatively large voltage range that goes from negative to positive at
> least -5vdc to +5vdc, originally was closer to -12 vdc to +12 vdc.
>
> If you tried to connect the RX/TX from an RS-232 port to a DS18S20 without
> building something like a DS9097U to create a 0-5vdc 1-wire bus, it won't
> work and it is possible your DS18S20 was damaged.
>
> The original DS9097* type devices converted from an RS-232 port down to a 5
> vdc 1-wire bus. I think most have a 5 volt regulator in them.
>
> There are simplified 1-wire bus adapters that connect to serial signaling
> that is at 0-5 vdc levels. These are for when you are using the output
> directly off the FTDI 232 or PL2303 or RPi or other system on a chip (SoC)
> pins that haven't gone through an RS-232 converter.
>
> The USB<->DB 9 serial adapter you are using has essentially two main
> components in it, a PL2303 USB<->Serial and an RS-232 convert, something
> like a max232 chip.
>
> If you ware building your own adapter, you want something like an FTDI or
> PL2303 "breakout" that doesn't have the converter. These are sold for
> microcontroller type projects for Arduino, RPi, serial consoles on embedded
> devices like wireless access points/routers, etc.
>
> Hope this helps,
> --Rob

Whoops, sorry I didn't see this thread earlier. Rob is spot on here, and
I second the recommendation for FTDI based USB->Serial adapters, I've
had no end of trouble with the PL2303 series.

You shouldn't be soldering RX and TX together, you should be using a
serial adapter. These days the DS9097U are cheap enough there's really
no reason to use the older-style DS9097 designs. Personally I like the
iButtonLink DS9097U compatible ones.

If you *really* want to build a DS9097 style adapter, see page 20 of the
App. Note 74 document - https://digitemp.com/docs/app74.pdf it has a
circuit that works.

Good Luck!

Brian

--
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