Huawei GPS board with LEA-M8T question - Page 1
Forum section: electronics / projects

author: MIS42N
author_rank: Frequent Contributor
timestamp: February 22, 2023, 11:19:59 pm
content: I bought a 'U-BLOX LEA-M8T-0-10 HUAWEI GPS Module Board'.https://www.ebay.ph/itm/333619130232The board is marked WD22UGRC. Most of the board circuitry is straightforward, low value resistors in data lines, spike protection etc. and checking the 8 pin connector matches the description in the linked advertisement.There are two transistors marked 3BW 95 (which I think are PNP), I don't know what they are for. I have searched but not found any information about this board. Does anyone have a description of the board or know what those transistors do?

author: bingo600
author_rank: Super Contributor
timestamp: February 23, 2023, 12:56:16 pm
content: I have no doc , and never seen any.A guess could be control/sensing of the Antenna power circuit

author: MIS42N
author_rank: Frequent Contributor
timestamp: February 24, 2023, 08:49:29 am
content: Quote from: bingo600 on February 23, 2023, 12:56:16 pmYou may be right. I am working through the 400 page manual for the LEA-M8T, and I thought it said it has the antenna monitoring on board, but maybe it needs help. There is no direct connection from the 'antenna power' pin on the connector and the antenna, it goes into a pin on the LEA-M8T via a 10Ω resistor.Anyhow, I bit the bullet. Set up a 3.3V supply, a serial to USB converter, and connected an active antenna and it works. Now I have to figure how to interface to my GPSDO.

author: MIS42N
author_rank: Frequent Contributor
timestamp: May 16, 2025, 02:42:21 am
content: I was asked if I had documented the Huawei WD22UGRC. No, but I have it working. Here is all I know:Pin 1 of the connector is next to the mounting hole, there's a small 1 on my board if I look carefully. Pinout top view:GND 8 7 nc1PPS 6 5 RXDnc 4 3 TXDVcc 2 1 antenna powerThis was documented elsewhere, I haven't found the link. The signals and Vcc are 3.3V. I don't know about the antenna power and suspect it can be other than 3.3V and may be controlled by the collection of small transistors. In my case the active antenna ran from 3.3V so I paralleled it with Vcc.To use the LEA-M8T in timing mode, it has to be surveyed in. To do this I configured a USB/serial adapter for 3.3V signals, and supplied Vcc/antenna from a 3.3V regulator connected to the 5V on the adapter.To interface with the GPS module, I used u-center 8.29. The module is configured by the TMODE2 message, and that doesn't seem to be available in later versions of u-center. I found u-center needed some learning. Configuring is done by adding the 'Configuration View' from the View drop down menu, then click on TMODE2, select survey-in and put in some survey parameters. From memory, this then had to be sent to the module. I don't have a module to connect at the moment to confirm. The module then does the survey-in, once complete it automatically enters Fixed Mode.If I remember rightly, other things can be configured and enabled by being sent. It is a while since I did this, but I think I limited the messages and also the satellite constellations. The changes are not permanent. To make them permanent there's an extra command which I don't remember. But I think u-center prompts for it.To use the board with my GPSDO (which expects a NEO-7M module with a 5 pin connection) I built a little adapter board with a 3.3V regulator on it, with pins like the NEO-7M module and the appropriate connector for the Huawei board. Also the active antenna had a BNC connector so I mounted a BNC socket on top of the existing connector, short wire to the active line.

author: rob040
author_rank: Contributor
timestamp: May 16, 2025, 04:49:22 pm
content: Hi,Thank you for the extra information, appreciate it!To be honest, I thought it would be plug & play, but besides the proper connections, I also have to configure some things. I did a quick look in the latest u-center program (25.03) and found the TMODE 2 setting. Default values are 24h and 1mm. I assume I have to play with it, because no clue what it does and what the effect of te values will be. But I guess that information could be found searching for the uBlox module.I'll proceed reading and learning.I have a 5V antenna, so I will try to figure out if I can add 5V to pin 1 without destroying the (uBlox) module.

author: MIS42N
author_rank: Frequent Contributor
timestamp: May 16, 2025, 11:54:18 pm
content: Quote from: rob040 on May 16, 2025, 04:49:22 pmThe LEA-M8T will work as a plug and play, if it wasn't set to fixed mode in its previous use. It then works like a better version of the NEO modules.In fixed mode the 1PPS becomes much more accurate, in my tests better than ±25ns. To set the values, just run it with the default for a day, it will finish when the time runs out. You can then look at the values it found, the distance is usually better than 1m. If it is greater than 1m, consider if the antenna is well located. Or if you want to try different antenna positions first just run short tests (say 5 minutes) and see which one gives the least distance, then run the 24hr test. I found the optimum using a program on a tablet then put the antenna there.

author: hgl
author_rank: Regular Contributor
timestamp: May 17, 2025, 01:58:45 pm
content: Quote from: rob040 on May 16, 2025, 04:49:22 pmThe GPS receiver automatically switches to TIME mode when both conditions are met. Set the 2nd parameter to 0.2m and wait 24 hours.You can monitor the progress with UBX:TIM:SVINQuote from: rob040 on May 16, 2025, 04:49:22 pmMost antennas work from 3.3V to 5V.I have (short-time) set the antenna to 5V. But did not get better levels.Try it with 3.3V.

author: rob040
author_rank: Contributor
timestamp: May 19, 2025, 06:13:59 pm
content: @hgl: Thanks, I will try that as well.In the mean time I tried to document the Huawei board. The PCB is a multilayer, so some things are an educated guess. The + of the battery (I assumed that is what it supposed to be) seems to be not connected.Edit: Pin 11 of the LEA-M8T is now connected to ground by means of R2. If a battery is required R2 has to be removed and next to R2 a jumper resistor can be placed. That connects the + of the battery to pin 11. Besides that, if a rechargeable battery is used there are reserved positions for a diode from pin 2 of the connector and a resistor to the + of the battery. Not been tested and documented by me.Please find the pdf attached.To proceed with the board, I need to order some stuff like a 2x4 2mm connector and, as proposed by MIS42N, a USB/serial adapter for 3.3V signals.

author: branco53
author_rank: Newbie
timestamp: May 26, 2025, 01:22:45 pm
content: Hi, can i ask you some things about lea-m8t huawey ? it is regarding startup, I have module connected to pc, u-center 21.2 not powered antenna, and see a lot of console messages, some times I see only une satellite, I think was a config problem, but not know how to go forward. Can you help me ? thank you

author: SpottedDick
author_rank: Regular Contributor
timestamp: July 12, 2025, 02:54:53 am
content: On the antenna.I have the chance to get a LEA-6T-2 module on a WD22UGRC board. However I have no clue what antenna I need. The connector looks odd as well, like it's almost a clip on rather than a screw?Can anyone give me a part number or *something* to lead me in the right direction?Thanks,SD

author: MIS42N
author_rank: Frequent Contributor
timestamp: July 12, 2025, 05:18:08 am
content: Quote from: SpottedDick on July 12, 2025, 02:54:53 amThe connector I believe is 50Ω SMB (SubMiniature version B). I had an antenna with an SMA plug, I just patched it in with a couple of paper clips and it worked. (advertised as active GPS antenna with 3m cable, very cheap). I have seen similar advertised with an SMB plug for a few more dollars. However, 3m did not get the antenna in an optimal position so I bought a mushroom style antenna with 10m RG58 cable and BNC connector. I soldered a BNC socket onto the SMB socket and wired it in parallel. Works fine. I think any antenna advertised as a GPS antenna will work in a reasonable reception area. I've had the cheap ones on a window ledge, on a garage roof, and various other places and they all work (I check with an app called GPS test on my Android phone to see where reception is reasonable. On the window ledge a few inches one way or other made a difference).

author: SpottedDick
author_rank: Regular Contributor
timestamp: July 12, 2025, 11:12:02 am
content: I suppose, from looking at the tech docs from uBlox on the LEA-6T, it gets so detailed that I assumed that I would need to specify the correct antenna. Not just grab any active GPS reciever with the right connector and cross my fingers. I suppose that's what I'll have to do though!On your short antenna @MIS42N - I have a uBlox Neo-7 module here that only came with a 1M antenna. I just added like 3-5M of RG-58 I had lying around by cutting the cable in the middle and soldering to it. I did take a long time at it, as I made sure the shielding stayed intact at the joint by pulling it back, then pushing it back over the joint, but it worked perfectly! Definitely a signal drop, but it allowed me to get the receiver on the roof, which more than made up for it!

author: ccb056
author_rank: Newbie
timestamp: July 27, 2025, 07:22:12 pm
content: I came across the attached circuit diagram for Board WD22UGRC (LEA-5T, LEA-6T, and LEA-M8T) hope this is helpful to someoneI do have a question on the 8 pin header - V_ANT - do I supply 3.3V to here from an external source (like I do on Vcc)? Just seems odd to supply 3.3V to both pins - so want to make sure.

author: rob040
author_rank: Contributor
timestamp: July 27, 2025, 08:30:06 pm
content: I think they separated the + supply pins because you may need +5V to feed the antenna.That is what I am going to do. If you need 3V3 for the antenna as well, I'm pretty sure you can tie both together.

author: MIS42N
author_rank: Frequent Contributor
timestamp: July 28, 2025, 01:24:27 am
content: Quote from: ccb056 on July 27, 2025, 07:22:12 pmYou need a supply on the V ant pin (as well as the 3.3V pin) for an active antenna. It won't work without it. And many thanks for the circuit.

author: bingo600
author_rank: Super Contributor
timestamp: July 28, 2025, 04:54:55 am
content: Quote from: MIS42N on July 28, 2025, 01:24:27 amI have an active 4-chan splitter, that powers the antenna via port 1.If i use a M8T on ie. ch2 , i don't need to power Vant ... But i do get an antenna alarm from the M8T.I'm trying to say : The receiver does not need Vant, in order to work .. Just the active antenna.

author: ccb056
author_rank: Newbie
timestamp: August 06, 2025, 10:53:56 pm
content: The Huawei WD22UGRC board looks very similar to the U-Blox RCB-F9T - at least from antenna placement, holes, header, form factor, etcI wonder if there are any enclosures that would work with this?