Tunika TD8620 connectors, Gaussmeter - Page 1
Forum section: electronics / testgear

author: jquinn11733
author_rank: Contributor
timestamp: July 23, 2025, 04:46:23 pm
content: I saw the older thread on the TD8620, after having purchased one. It is a Gaussmeter available in 1%, 2%, and 5% models. It goes up to 24KGauss. I have compared it to my venerable FWBell model 4048, and get similar results (within mutual errors). Inside the rear battery-cover are to unadvertised connectors.Could someone help me determine if I can use these to export digital data? Greatly appreciated. - Jim jquinn11733@gmail.com

author: Kean
author_rank: Unknown
timestamp: July 27, 2025, 08:11:12 am
content: I know nothing about this device, but it doesn't seem hard to identify the connections as a lot of signals are labelled on the other side at the unpopulated 12 pin connector at the bottom.The 6-pin connector labelled COM1 will be communications, but without experimentation we don't know what it implements in terms of functions or protocol. You'll basically just need to connect something to it and see if anything comes out, and if so experiment with baud rates until it looks sensible. Often these devices just dump a reading once a second in plain text, but sometimes the data is binary or requires a query command in a certain format.My guesses are as follow: (Edited to swap pin 1 & 2)Pin 1 is receive data, and probably no too useful if you don't have software or documentation for the protocolPin 2 is transmit data, and probably what you are most interested inPin 3 is hard to tell, but I'm guessing GND due to the protection diodes - you can check continuityPin 4 is 3.3V (output from the device)Pin 5 is unknown - maybe another GND connection to pair with pin 6Pin 6 appears to be a 9V power input, but diode D5 isn't populated so it probably doesn't have any functionI would also guess that these are 3.3V level UART signals, so you will need a 3.3V USB to serial adapter, and initially just connect GND and pin 1 TX to the USB to serial RX pin. Pin 1 on this connector is the square solder pad on the left of photo C, so on the right of your photo B. Edit: this is actually the reverse pin order of a JST PHR-6.The 4-pin connector labelled JTAG1 (and most of the 12-pin unpopulated connector) is probably something you should avoid unless you know what you are doing.

author: Kean
author_rank: Unknown
timestamp: July 27, 2025, 08:19:49 am
content: LOL, I just realised that I have actually one of these devices - but I've never actually used it as it arrived last year while I was in hospital.I think joeqsmith bought one, so I wouldn't be surprised if he has already attempted connectivity...If I get a chance in the next week I will dig it out and see if I can get any data from it.

author: Kean
author_rank: Unknown
timestamp: July 28, 2025, 06:01:10 pm
content: I managed to find where I had stashed my TD8620 and did some initial tests where I made up a test cable, and realised that I mixed up pins 1 & 2 below (now edited).** Note that the connector is a JST PH 6-way, and pin order is actually reversed compared to the JST standard. I'll continue to use pin order based on the pin 1 marked on the PCB.Using pin 3 as 0V reference, I see 3.3V on pin 2 and 4 and this matches what I would expect. I see a small voltage (like 0.3V) on pin 1, which would make sense if it is RX and a floating input.I do not see any data transmission, nor did I get any response trying random keypresses (enter, ?, etc) at a few different baud rates.I have emailed Tunkia to see if they will provide any information.https://www.tunkia.cn/contactus.html

author: Kean
author_rank: Unknown
timestamp: July 29, 2025, 08:31:13 am
content: OK, I got a quick reply from someone at Tunika.QuoteSo it is not supported/implemented unfortunately, and almost impossible to do anything without their help.Maybe if some other people were to ask about this they will get the hint...Edit: Actually Tunika have shown some interest in more feedback, so anyone is welcome to let me know (or contact them directly) about your use case. This doesn't mean they will offer firmware updates (I'm not sure yet that is actually supported), and it may just lead to them try suggesting/upselling to a more expensive product.

author: jquinn11733
author_rank: Contributor
timestamp: July 29, 2025, 02:06:39 pm
content: Kean -Thank you so VERY much for showing interest in this topic.I greatly appreciate it. You have motivated me to contactTunika. Also, motivated me to probe these pins (thoughthis is new for me).kind regards,- Jim