GNSS module Allystar TAU1302 has fix but does not output PPS
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I have a microcontroller board Datagnss Tiny EVK with an integrated chip TAU1302 (Allystar). I can get a fix with expensive Tallysman antennas in a rural area, with over 30 satellites and SNRs exceeding 40. I can see L1 , L2C, and L5 bands , at will.
A blue LED is supposed to light up indicating that the PPS signal is pulsing after a fix. I have never seen this blue LED turn on, ever. All documentation, guides and datasheets for this module indicate that it should simply come on after a fix. I have never seen this happen. With oscilloscope, I measure the PPS line from a molex launch. It is always emitting a 2.5V square wave at 60Hz. It emits that no matter the condition — indoors, outdoors, fix, no fix. So I know my mechanical circuits are connected correctly.
How do I make this module begin to output PPS? Do I need to send a command of some kind through the RX/TX serial? If anyone has seen something similar with UBlox GNSS modules, please leave a reply, even if it does not match my hardware exactly.
More below the images.
I have used the software for this module, which allows me to send commands through the USB acting as a UART. I have tried setting the duty cycle and GPIO number to 3, and none of this makes any difference. Even after properly sending (rather than “polling”) the commands never stick after leaving the menu and returning again.
Module regularly receives GNGGA NMEA sentences. On those I see what the docs call a GNSS quality indicator which is a single digit number. This is shown in the table below.
I have only ever seen 1 in that sentence. Note the “(values above 2 are 2.3 features)”. Nothing in this document nor others indicates what 2.3 features means. I can only speculate that it refers to an RTCM protocol, shown here from a website
Here is the entirety of all documentation, guides, manuals and datasheets that exist for this board.
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