Samsung UCCM modules STP2945LF 1PPS out - Page 1
Forum section: electronics / general

author: KC0SKM
author_rank: Newbie
timestamp: January 29, 2021, 02:38:00 pm
content: I am having problem getting the 1PPS off the board - I have enable and disable PPS using Lady Heather, have a solid locked 10 MHZ reference out. I am not sure what I am missing using Lady Heather version 6.14. I made sure my cables to scope, nothing is damaged on the board I can see. Shows PPS enabled on Lady Heather software.. Also on the pin on the ribbon cable that is the 1 PPS or what I have read show no 1 PPS.

author: cdev
author_rank: Super Contributor
timestamp: January 30, 2021, 05:16:19 pm
content: Maybe attached PDF (orthis time-nuts thread) will help you out?Also, there is a CLI on the command UART which was discussed here a few days ago.

author: KC0SKM
author_rank: Newbie
timestamp: February 01, 2021, 02:26:01 pm
content: Thank you for the reply I have grounded pin 38-39. ( I had found that pin out a few days back thanks again this is touch to find more post will make it easy to find the pinouts) What I have read it seems (from others post) that 1 PPS comes up with out any effort or commands. My unit is locked it has 10+ gps sat locked. It is a solid 10 MHz locked output. but still nothing out of the 1 PPS port (not that I needed it but it would be nice to have). The unit is connect to lady heather and tried all the enable and disable 1 PPS commands. I have a friend that has a board he has not tried and he will bring over for comparison. I have read the time nuts article, feel I have gleam everything I can from that reference you provided it seems that Nigel did nothing to enable 1 PPS? For sure you need to ground pin38-39 to use GPS or the device alarms and only a sub standard 10 MHZ reference is output.. I am not sure where the other post is but will search this forum for it.. KC0SKM

author: KC0SKM
author_rank: Newbie
timestamp: February 01, 2021, 02:32:09 pm
content: other link for referencehttps://www.eevblog.com/forum/metrology/samsung-uccm-gpsdo-reverse-engineering/msg3430972/#msg3430972

author: cdev
author_rank: Super Contributor
timestamp: February 03, 2021, 02:37:01 am
content: Some 1PPS signals are so short they are difficult to detect. So then people have rigged up pulse stretchers that lengthen their duration.This situation is actually fairly common.Quote from: KC0SKM on February 01, 2021, 02:26:01 pm

author: cdev
author_rank: Super Contributor
timestamp: February 03, 2021, 02:47:56 am
content: It will be nice to have such an accurate means of determinining frequency and time intervals "on tap".

author: cdev
author_rank: Super Contributor
timestamp: February 03, 2021, 02:58:45 am
content: Quote from: KC0SKM on January 29, 2021, 02:38:00 pmThats good, in that you don't want 1PPS to be provided unless it is justified, because it is supposed to provide verification that the data is good enough to be fairly certain of its accuracy. (in both time and 3D's of position)Where I live we just had a blizzard and as of yesterday, there is a huge amount of snow, so much that I would not be surprised if it blocked the GPS signal. There was so much snow that we could barely open the door. (They said 20 inches.) Very heavy, dense icy snow.

author: rf-loop
author_rank: Super Contributor
timestamp: February 21, 2021, 04:43:14 am
content: Quote from: cdev on February 03, 2021, 02:37:01 amSamsung UCCM 1pps is not very short. Around 50us.This is not from just same model but "mostly compatibe".Supply voltage need be inside 5.30 - 5.70 V measured from board. Best place to measure is GND and on board Fuse end. This flat film cable have resistance and it is best all GND and all VCC 5.5 V terminals need be connected for avoid voltage loss. In startup it takes nearly or even over 2 A current and after temp is ok still around 0.8-0.9A.Here 1pps out image. Directly from J4 to oscilloscope HiZ input. It can also terminate 50ohm but voltage is then bit over 1 V (in mine all three units around 1.17 V. Upper window can see 2 1pps pulses and bottom just one zoomed.Btw, there is also one other way to get "pps" out. 50pin conector pin 2. It is fast UART TX TTL. It start message every second. If just detect start it can use as pps. I can not now check if it give out really 1 message per second or 1 message every 2 second. But this I remember when I have measured that it is sync with 1pps.Also, of course, this J4 1pps is tightly sync with 10MHz Sine out from J3.1PPS out from Samsung STP2878LF

author: cdev
author_rank: Super Contributor
timestamp: February 22, 2021, 06:17:18 pm
content: I have that exact same model, as of yet Ive been too busy to do much with it besides verify that it works. I'd be happy to turn it on and get it running continuously and sniff any signal you would like me to, get a screenshot with my digital sampling scope, so you have a comparison. I have verified 1PPS is working with an LED. (Thats a good way to do it.)

author: cdev
author_rank: Super Contributor
timestamp: February 25, 2021, 05:04:31 pm
content: Ebay user zyt_gps appears to have made an information rich monitor program for UCCM GPSDOs.I don't know anything about it, what platforms it runs on, etc..