[time-nuts] Re: Lpfrs-10 serial port failure

[hb9dri at bluewin.ch]

Dear Steve and Brian

Thank you very much to you guys, your quickly comment point me to the problem and now IT WORKS!!
I'm so happy to type now V and receive al information, here a printout:

V
TNT/LPFRS01 Rb Version 2.07 29/5/07 Checksum: 2973/EA11
M
7F 77 B8 A1 85 68 AB E2
M
7F 76 B8 A1 85 6A AB E1
M
7F 76 B8 A1 85 69 AC E0

L06 (this is query for the Coarse tunning value)
78
L0A (this is the query for the Fine tunning value)
0D

Ther logic was inverted, to fix I use a 74AC14 and place an inversor gate in each line (TX and RX) and that's all, the LPFRS-01 start to singing like opera singer

As you see now I have access to all parameters and I will have the chance to do a properly calibration against a Caesium source, quickly I build a Arduino NANO sketch and it decodes each hexadecimal answer in decimal values, means I'm able to read directly on the screen the Dc voltage on the photocell, the Rb signal level, the Varactor control voltage (VCXO), the Frequency adjustment voltage, the Rb lamp heating limit current together with the Rb cell heating limit current and her 90 Mhz power control, last at not least and very important the Cxx and Fxx values, as you see in my print our my device has a Coarse of 78 and a Fine of 0D.

Additionally I create a excel table with 65537 entries where is calculated  the Cxx values in decimal and Hexadecimal, the Fxx values also in decimal and Hexadecimal, with the total correction in Hz/Hz, in ppb and deviation in Hz, the Coarse value start in 80 HEX (-128 decimal) and finish in 7F HEX (+127 decimal) each Coarse position has 128 Fine calibration points, now will be easy to calibrate the unit.

Thank you, guys, and also to the reflector, if some body is interested in the Arduino program to read and convert all LPFRS-01 parameters in decimal values and in the Excel sheet for calibrate the LPFRS-01 just give a shout.

73 de Alex, HB9DRI

-----Original Message-----
From: Steve Hendrix, P.E. via time-nuts <time-nuts at lists.febo.com> 
Sent: Friday, 21 November 2025 11:41
To: time-nuts at lists.febo.com
Cc: Steve Hendrix, P.E. <SteveHx at HxEngineering.com>
Subject: [time-nuts] Re: Lpfrs-10 serial port failure

It's possible the logic levels are inverted. Standard RS-232 is a positive voltage for a 0, negative for a 1, whereas most TTL level interfaces use 5V for 1, 0V for 0. Although it doesn't fully meet the spec, sometimes interfaces are built using TTL to directly interface to RS-232, counting on the fact that most "RS-232" interfaces actually tolerate a transition level somewhat positive of ground. Your description of detecting a Break condition suggests that you need to invert the signals.

Steve Hendrix

On 2025-11-21 1:34 AM, Bryan _ via time-nuts wrote:
> Hmm, looked at the manual available online and it appears your settings are correct. I did see this note, but don't see a schematic to the referenced adapter circuit in the manual.
>
> IMPORTANT NOTE In most cases, the serial PC interface accepts the 0 to 5V level and a direct connection can be made. In case this 0 to 5V standard is not working , please refer to the small adaptation circuit called ‘ RS 232 adapter circuit’ described in annex I.
>
> -=Bryan=-
> ________________________________
> From: HB9DRI, Alex Artieda via time-nuts <time-nuts at lists.febo.com>
> Sent: November 20, 2025 9:40 AM
> To: 'Discussion of precise time and frequency measurement' 
> <time-nuts at lists.febo.com>
> Cc: hb9dri at bluewin.ch <hb9dri at bluewin.ch>
> Subject: [time-nuts] Re: Lpfrs-10 serial port failure
>
> Hello Brian
>
> I have no idea with the previous owner, I follow what the manual said:
>
> The data transfer from the LPFRS can be made by direct connection to a 
> PC or standard terminal.
> The data transfer parameters are the following:
>
> bit rate: 1200 bits
> parity: none
> start bit: 1
> data bits: 8
> stop bit: 1
>
> My device is flag as TTL means logical levels 0 to 5vdc following 
> standar logic, some information in internet spoke about (RS232, TTL) 
> but the label on my device spoke just TTL, a pure RS-232 will involve 
> positive and negative voltages.
>
> I try with puTTy, RealTerm, and Hyperterminal, configure echo, just a 
> important observation in RealTerm when connect the device the Terminal 
> said (BREAK CONDITION DETECTED) and the Led BREAK is RED.
>
> I assume the serial interface is damage, that is the reason of my post.
>
> 73 de Alex, HB9DRI
>
> -----Original Message-----
> From: Bryan _ via time-nuts <time-nuts at lists.febo.com>
> Sent: Thursday, 20 November 2025 17:20
> To: Discussion of precise time and frequency measurement 
> <time-nuts at lists.febo.com>
> Cc: Bryan _ <bpl521 at outlook.com>
> Subject: [time-nuts] Re: Lpfrs-10 serial port failure
>
> Did the unit work before when connecting via serial. What protocol are 
> you using to connect via serial.
>
> -=Bryan=-
> ________________________________
> From: HB9DRI, Alex Artieda via time-nuts <time-nuts at lists.febo.com>
> Sent: November 19, 2025 11:52 PM
> To: time-nuts at lists.febo.com <time-nuts at lists.febo.com>
> Cc: HB9DRI, Alex Artieda <hb9dri at bluewin.ch>
> Subject: [time-nuts] Lpfrs-10 serial port failure
>
> Dear friendsIm totally new in this list, looking for a solution to a 
> problem with my Lpfrs-01.I had this unit second hand, in optical an 
> funtional pristine condition , take only 3min to lock. All looks good 
> except I cannot connect to the serial port, the device specified TTL 
> Rx and TX in the lable, no response at all when send M, when is 
> connected to a USB uaart converter and I send M the TX line show a 
> permanent 3.6vdc and a train of pulses show up in the oscilloscope, at 
> the same time the DXine is clamp to 1.4vdc and nothinig appears, 
> suspect the serial interface buffer is damage.I will apprecite some 
> advice to repair the unit, I try tl fk d a diagram with no success, 
> only few tier down photos, maybe some body can point me where I xan 
> sfart looking, maybe a IC to replace.Any help is welcome.73 de Alex, 
> HB9DRISent from my Galaxy 
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