RT-900 "Deaf"/Off Frequency issue clue
Added 2025-05-18 17:52:39 +0000 UTCI just got my radio into this state again and noticed something else. When transmitting there is no TX Modulation. I always have the TX Mod Meter turned on and while testing trying to find out exactly what frequency it was transmitting on during this state I noticed the TX Mod Meter was not moving when I spoke, even though the tx mod meter was on and mic gain and TX Deviation were turned up.
I think the BK4819(4829) has "crashed" if that's even possible. The symptoms for this problem are too bizzarro and random and this idea seems to fit. There's a couple of things I can try here. Change the timing of the data transfer and/or figure out a way to detect if the chip is in an unstable state and issue a reset sequence.
The reason i suspect this is because the RT-900 is already notorious for poor circuit design. If the VCC of that BK4829 is not particularly well bypassed or the power rail used to power it is not adequately filtered, it might very well cause the chip to randomly become unstable. Maybe the stock firmware has a way to detect this and reset the chip?
The debug dumps supplied from members testing .11 have been very useful, so thank you all for taking the time to do that for me.
Comments
I'm not sure how accurate the AI is there, those register descriptions seem quite different to the Beken documentation. Also it talks about the chip having registers for battery status which would seem very odd?
David
2025-05-20 08:27:52 +0000 UTCDeepseek seems to have info on the BK4829 and knows the differences Certainly! Below is a detailed comparison of the register tables for the **BK4829** and **BK4819** RF transceiver ICs. These chips are commonly used in two-way radios and walkie-talkies, particularly in models like the **Baofeng UV-5R** (which uses the BK4819) and some of its variants. --- ### **BK4829 vs. BK4819 Register Comparison** Both ICs share many similarities since the BK4829 is likely an updated or modified version of the BK4819. However, there may be differences in register functionality, bit assignments, and additional features. #### **Common Registers (Shared Functionality)** | **Register Address** | **BK4819 Function** | **BK4829 Function** | **Notes** | |----------------------|---------------------|---------------------|-----------| | **0x00** | Chip ID / Version | Chip ID / Version | Likely identical or similar | | **0x01** | System Control | System Control | Controls power modes, resets, etc. | | **0x02** | PLL Control | PLL Control | Frequency synthesis settings | | **0x03** | Modulation Control | Modulation Control | FM/AM settings, deviation, etc. | | **0x04** | Squelch Control | Squelch Control | Squelch threshold, noise detection | | **0x05** | Volume / Audio Control | Volume / Audio Control | Audio gain, pre-emphasis, etc. | | **0x06** | RX Control | RX Control | Receiver settings (bandwidth, etc.) | | **0x07** | TX Control | TX Control | Transmitter settings (power, etc.) | | **0x08** | RSSI / Signal Strength | RSSI / Signal Strength | Received signal strength indicator | | **0x09** | Battery / Power Status | Battery / Power Status | Voltage monitoring, low-batt detection | | **0x0A** | GPIO / Pin Control | GPIO / Pin Control | General-purpose I/O settings | | **0x0B** | CTCSS / DCS Control | CTCSS / DCS Control | Tone squelch settings | | **0x0C** | DTMF Control | DTMF Control | DTMF encoding/decoding | | **0x0D** | Miscellaneous Control | Miscellaneous Control | Various auxiliary functions | | **0x0E** | EEPROM / Flash Control | EEPROM / Flash Control | Memory access (if applicable) | | **0x0F** | Test Mode / Debug | Test Mode / Debug | Factory testing, diagnostics | --- ### **Key Differences (If Any)** 1. **Frequency Range & Step Size** - The **BK4829** might support a wider frequency range or finer tuning steps compared to the BK4819. - The **PLL registers (0x02)** may have different bit configurations for frequency synthesis. 2. **Modulation & Filtering** - The **BK4829** could have improved FM modulation settings (Register **0x03**) or better filtering options (Register **0x06**). 3. **Additional Features** - The **BK4829** might introduce new registers for features like **APRS, Bluetooth control, or enhanced power management**. 4. **Power Management** - The **BK4829** may have more granular power control (Register **0x01** or **0x09**), improving battery efficiency. 5. **Compatibility** - Some registers might be **reassigned** or **repurposed** in the BK4829 compared to the BK4819. --- ### **Conclusion** - The **BK4829** is likely an **updated version** of the BK4819, with possible improvements in frequency handling, modulation, and power efficiency. - Most **register addresses are the same**, but some **bit-level configurations** may differ. - If you're working with a radio that uses the **BK4829**, it's best to check the **official datasheet** (if available) or compare against known BK4819 register maps.
Allerley
2025-05-20 07:06:08 +0000 UTCThey look real close on the specs and foot print except slightly shorter frequency limit on the high end. I think maybe you guys are on the right track. I wonder what registers are available and what might have changed.
Ken
2025-05-20 01:24:14 +0000 UTCIf what I suspect about what is happening is right, the trigger could be infinitely variable from radio to radio. Since I have tidied up the SPI and timing in .12 (when released) please test your trigger on .12 (when released) and see if it still occurs, it won't mean it's fixed but it would be strong evidence that what I suspect is true.
Marcus Dudley
2025-05-20 01:14:49 +0000 UTCI finally had some time mess around with the rt-900 and noticed that if I have Sq Tail Elim turned off, I don't get any frequency shift that I have noticed. Once I enable Sq Tail Elim for any option, it transmits correctly until it receives any transmission on the set channel. Then it's transmitting way over frequency. Only way to fix it is to disable Sq Tail Elim and power cycle radio. This is on v11.
Scott Stone
2025-05-19 22:19:32 +0000 UTC
