[Question]Modbus Read command issue DMG10600C070_03WTC

vas_teplocom

Model: DWIN DMG10600C070_03WTC
OS kernel: DWINOS_DWIN_T5L_115200__UART4_ModBus.bin (downloaded from the "DWIN_T5L_115200_UART4_MODBUS_Master" package)
DGUS Tool project: 4 Data Variable Display icons, VP 0x5000-0x5003, type int (2 bytes, signed)

Issue: In Modbus RTU master mode, WRITE instructions work correctly (master writes VP value to slave register, confirmed on slave side), but READ instructions never update the on-screen display, even though the RTU bus traffic confirms the slave is answering correctly.

22_config.bin content (offset 0x1C000):
5A 01 03 01 30 00 00 00 50 00 00 02 00 00 00 00   (read slave reg 0x0002 -> VP 0x5000, unconditional)
5A 01 03 01 30 01 00 00 50 01 00 04 00 00 00 00   (read slave reg 0x0004 -> VP 0x5001, on page 0)
5A 01 06 01 30 04 00 00 50 02 00 01 00 00 00 00   (write VP 0x5002 -> slave reg 0x0001, on VP change)
5A 01 06 01 30 00 00 00 50 03 00 00 00 00 00 00   (write VP 0x5003 -> slave reg 0x0000, unconditional)

RTU sniffer log confirms correct bus traffic for the read instructions, including the slave register value actually changing (0x05 -> 0x0A) when I changed it on the slave side:
Rx: 01 03 00 02 00 01 25 CA
Tx: 01 03 02 00 05 78 47
... (repeats)
Rx: 01 03 00 02 00 01 25 CA
Tx: 01 03 02 00 0A 38 43   <- value updated correctly on the wire after changing it on the slave

So the Modbus RTU exchange itself is 100% correct (verified with an RTU sniffer and by intentionally changing the slave register value mid-test), but the value never appears in the Data Variable Display icon bound to VP 0x5000 on the panel screen.

I also tried:
- Moving the VP addresses to 0xE000-0xE003 instead of 0x5000-0x5003 (icons + 22_config both updated) - no change, read still doesn't show, write still works.
- Add the 5A A5 enable header and starting the 4 instructions directly at 0x1C010 instead of 0x1C000 - no change.
- Reading VP 0x5000 directly via DGUS Tool's Debug/VP monitor tool (5A A5 04 83 50 00 01) while the master polling loop was running - got no response at all from the panel to this debug read request, while the RTU master polling continued normally in the background.

Questions:
1. Is there a known issue with READ instructions (function 0x03) not updating the display VP correctly on this OS kernel, while WRITE instructions (function 0x06) work fine?
2. Could the continuous/unconditional Modbus master polling loop (no configurable interval, instructions run back-to-back nonstop) be blocking or delaying the panel's internal VP-write-to-display refresh step, or blocking response to DGUS debug commands (5A A5) sent over the same UART?
3. Is there a different/updated OS kernel version needed for correct READ instruction handling on this panel model?

Any help identifying why READ instructions don't reach the display, while WRITE instructions work correctly with the same file/instruction format, would be greatly appreciated.

ZVIP7679

You can try using the source code on the 2nd floor here. For this link, the 03 instruction is fine. This is the most commonly used instruction.
【Development Materials】T5, T5L Series MODBUS_RTU Protocol Communication OS Source Code - Upgrade Version http://inforum.dwin.com.cn:20080 ... 9&fromuid=54868
(Source: Diven Technology Forum)

Also, when looking at the Modbus communication transmission and reception instructions, the process is fine. In this case, it is possible to check the DGUS engineering interface to see if there are any issues.

vas_teplocom

That didn't work for me

紫狐

The kernel file DWINOS_DWIN_T5L_115200__UART4_ModBus.bin is fully functional. Display the value at address 0x5000 using data variables, and send images to check the control properties and screen display.

vas_teplocom

紫狐 发表于 2026-7-15 08:52
这个DWINOS_DWIN_T5L_115200__UART4_ModBus.bin内核是可以正常使用的。用数据变量显示看下0x5000地址的值， ...

Here are all screenshots. As you can see my variables that have VP 0x5002 and 0x5003 shown on display when I change values but my display dont show real values from slave.

紫狐

Could you send the burning file?

vas_teplocom

紫狐 发表于 2026-7-15 18:19
烧录文件方便发下吗？

This is what you asked for?

紫狐

vas_teplocom 发表于 2026-7-15 18:42
This is what you asked for?

Yes, I'll test it out

紫狐

The program is fine; check the hardware wiring to see if the RX4 of the screen is properly connected.

vas_teplocom

紫狐 发表于 2026-7-16 08:40
The program is fine; check the hardware wiring to see if the RX4 of the screen is properly connected ...

I use RX2/TX2 to upload files to the display, and RX4/TX4 to verify functionality. As far as I can tell, everything is connected correctly.