exFW880 V4
Added 2025-07-01 13:55:07 +0000 UTCI’m excited to share my diagnostic firmware designed to help probe and identify the functions of various GPIO pins on the device. Using this firmware, I’ve already mapped out the VHF/UHF filters for both RX and TX. However, since I don’t have access to proper HF testing equipment, I haven’t been able to fully verify the HF transmit functionality. If any brave users want to experiment and help figure it out, your feedback would be greatly appreciated! I also do not yet know if there are specific HF filters on the BK4819 GPIOs relating to HF.
Important Safety Notice:
Please be aware that changing GPIO settings and filter configurations without caution can potentially cause physical damage to the radio hardware. While a well-designed system should prevent this, it’s not something we can guarantee, so please use this firmware responsibly and at your own risk.
A key recommendation:
Only one BK4819 GPIO pin should be set to ‘1’ at any time. Activating both RX and TX stages for the same band simultaneously and transmitting could damage the receive finals. Take care to avoid this scenario.
Usage Instructions:
V3
Keys ‘0-9’: Enter new frequency
Key ‘#’: Toggle antennas
Button ‘S1’: Toggle HF TX Enable
Button ‘S2’: Toggle HF TX 29M/50M band
Long press ‘0-6’: Toggle BK4819 GPIO pins
PTT: Transmit
Note: It should transmit at FULL power, take care.
V4
Long Press 'S2': Override squelch toggle.
Key '*': Swap BK4819 Chip
Key 'UP': Toggle ANC
Key 'EXIT': Change modulation
Comments
Well that GPIO should only be enabled during TX, so yeah, I imagine it would have negative effect on RX.
Marcus Dudley
2025-07-03 09:08:36 +0000 UTCYeah, it's unfortunate if so. I could have done so much with dual receive.
Marcus Dudley
2025-07-03 09:07:12 +0000 UTCill play with this tonight. may be the second BK is only for the repeater function? i remember a video months ago of somebody untearing the unit and describing blocks... have to look for it.
Ramon Martinez Palomares
2025-07-03 09:05:02 +0000 UTCHF TX ENA: if disabled, improves a lot HF RX. GPIO 1 and GPIO6: playing with them while in FM broadcast frequency, are modifying audio quality.... may be bandwidth?
Ramon Martinez Palomares
2025-07-03 06:57:22 +0000 UTC
