I bought a used lot of bits and I’m trying to identify what I have.
One is apparently an “F4_SVTX”, and I’m trying to find a spare uart to wire in an ELRS rx, and I’m seeing pads labeled P/D, P01, P02, etc but I don’t know what those mean. Also, it has an unidentifiable 4 in 1 esc.

Second one is apparently an HGRLC “microF4” stack, but I can’t find anything that looks like it on HGRLC’s site. Also looks like one of the chips on the 4 in 1 esc is toast.

Last one doesn’t seem to have any identifying info on it at all, but has an arm stm32f405 chip on it.

(The pictures with 3 boards includes the hglrc stack and the unidentifiable FC (slightly farther away)

The HGLRC FC is from an HGLRC XJB F425 Flytower stack.

Specifications:

• Brand Name: HGLRC
  
• Item Name: 20x20mm Micro F4 Flight Controller
  
• MPU: MPU6000-SPI
  
• CPU: STM32F405RGT6, dual 8K
  
• Black Box: Flash 16M
  
• Input Voltage: 2-4S Lipo
  
• Built-in Betaflight OSD to adjust PID
  
• BEC Output: 5V@3A
  
• Size: 25x25mm board, 20mm mounting holes (M2)
  
• Weight: 2.3g
  
• Support Subs/PPM/DSMX receiver
  
• Usage: Original Parts for HGLRC XJB F425 F428 Series Flytower
  

The RCX Hobby F4_SVTX FC/VTX only has 2 UARTS. UART1 only appears to have the RX pad broken out on the board for either SBUS or DSM/PWM with UART2 internally connected for IRC Tramp control of the VTX. There are 4 unlabelled pads in the middle of the board but it's not clear what they are for. You could try doing some continuity checks on them with a multimeter to see if they are connected to GND, the 5V rail, or any of the MCU pins. If you find that any are connected to any MCU pins then post a CLI "dump" and we can then figure out what they are for.

4_SVTX Flight Controller Specifications:

• Processor: STM32F411C
  
• Sensor: MPU6000
  
• OSD: AT7456E
  
• Input voltage: 2S-4S (7-17V)
  
• Built-in BEC: 5V 1A
  
• Receiver support: PPM/SBUS/DSM2/DSMX/IBUS, etc.
  
• Reserve interface: power battery input VCC GND
  
• Motor Drive Signal PWM1-PWM4
  
• LED_STRIP
  
• Buzzer
  
• LC filter
  
• Supports PWM, Multishot, Oneshot, DSHOT, PROSHOT and other ESCs
  
• Online tune Betaflight
  
• Suitable rack: 80-160MM model
  
• Dimensions: 27*27MM
  
• Screw hole distance: 20MM*20MM
  
• Inner hole diameter: 2.5MM
  
• Weight: 3.2g
  

5.8G 48CH 25/100/200mW VTX Specifications:

• Power: 25/100/200mW switchable
  
• Channel: 48CH
  
• Frequency switching: manual button / OSD (supported simultaneously)
  
• Antenna interface: IPEX
  

Thank you, you’re awesome. I’ll do some probing and hopefully find a pad connected to an mcu pin, then do a cli dump this weekend.

(I’m assuming by mcu you mean microcontroller? IE: main f4 chip?)

Whelp, I just realized the F4SVTX is missing the usb jack, so I’ll hafta sort that out. It looks like the 4 pads in the middle of the board are all routed to a chip labeled “so33 phv6 714y”.

The other so far unidentified FC looks like it’s missing something (see red circled area). I can’t tell if it’s missing some 6 pin chip that should be inline with the video out, or if it’s just missing a connector.

I’ve really gotta stop buying lots of random old questionable gear. Still, with this one I ended up with 7 good 1106 5500kv motors, multiple working vtx, 2 cameras and 2 frames for $60, so I still feel like I got my money’s worth.