FPort telemetry with Matek F405-STD not working

[lo4wai]

Board and Version

Matek F405-STD INAV v.1.9.1

Behavior

I connect the uninverted smart port pad of R-XSR receiver to TX port, and configure FPort as serial rx. The RC link work fine, but my X9D+ cannot discover telemetries other than Rxbt and RSSI.

I have tried all UART ports, RC link work but not telemetry. I tested the UART with TRAMP vtx and it work fine. I believe that bidirectional serial is working on these UARTs.

FPort telemetry work on my other boards such as Matek F405-OSD or Omnibus F4 v3.

Below is the diff with the uninverted smart port connected to UART 4 tx.

diff

version

INAV/MATEKF405 1.9.1 Apr 21 2018 / 13:25:29 (03a5c1922)

resources

mixer

mixer CUSTOMTRI mmix 0 1.000 0.000 1.333 0.000 mmix 1 1.000 -1.000 -0.667 0.000 mmix 2 1.000 1.000 -0.667 0.000

servo mix

smix 0 5 2 100 0

servo

servo 5 1000 2000 1500 -93 -1

feature

feature GPS feature LED_STRIP feature BLACKBOX feature PWM_OUTPUT_ENABLE

beeper

beeper -ON_USB

map

name

serial

serial 0 0 115200 38400 0 115200 serial 1 2 115200 115200 0 115200 serial 2 0 115200 57600 0 115200 serial 3 64 115200 57600 0 115200 serial 4 4096 115200 57600 0 115200

led

color

mode_color

aux

aux 0 0 0 1300 2100 aux 1 1 1 1300 2100 aux 2 20 0 1675 2100 aux 3 3 2 1675 2100 aux 4 9 2 1300 1700 aux 5 8 2 1700 2100 aux 6 11 4 1725 2100

adjrange

rxrange

master

set acc_hardware = MPU6500 set acczero_x = 7 set acczero_y = -8 set acczero_z = -59 set accgain_x = 4095 set accgain_y = 4091 set accgain_z = 4101 set mag_hardware = HMC5883 set mag_declination = -250 set magzero_x = -48 set magzero_y = -28 set magzero_z = -31 set baro_hardware = BMP280 set pitot_hardware = NONE set rssi_channel = 16 set serialrx_provider = FPORT set serialrx_halfduplex = ON set min_throttle = 1010 set max_throttle = 2000 set motor_pwm_rate = 2000 set motor_pwm_protocol = ONESHOT125 set failsafe_procedure = RTH set vbat_scale = 1093 set vbat_max_cell_voltage = 420 set battery_capacity = 3000 set battery_capacity_warning = 1800 set battery_capacity_critical = 900 set current_meter_scale = 151 set current_meter_offset = -3 set servo_pwm_rate = 330 set small_angle = 180 set gps_sbas_mode = MSAS set nav_extra_arming_safety = OFF set telemetry_inverted = ON set smartport_fuel_unit = PERCENT set osd_main_voltage_pos = 2168 set osd_rssi_pos = 2116 set osd_throttle_pos = 225 set osd_vtx_channel_pos = 88 set osd_current_draw_pos = 2232 set osd_mah_drawn_pos = 2264 set osd_gps_speed_pos = 2243 set osd_gps_sats_pos = 2147 set osd_home_dir_pos = 2411 set osd_home_dist_pos = 2414 set osd_altitude_pos = 2275 set osd_vario_pos = 2231 set osd_main_cell_voltage_pos = 2200 set osd_throttle_auto_thr_pos = 2370 set osd_heading_graph_pos = 2154

profile

profile 1

[lo4wai]

Finally got it work by using the original inverted smart port pin from the R-XSR and connected to uart4, enable softserial and set serialrx_inverted to ON. It doesn't work if the receiver is connected through the uninverted pad.

I found that uart pads in this board is not directly connected to the processor pin, but through a resistor instead. I guess signal from FC after passing through the resistor may not be strong enough to be recognized by the rx without the inverter.

[rhwilr]

Thanks, @lo4wai this helped a lot! I just had the exact same issue. I shorted out the resistor by soldering a thin wire over it. This solved the problem for me.

[fiam]

@lo4wai Thanks for figuring this one out. Not closing it yet, since we might to mention this workaround in the wiki.

[fl0zan0]

hi do you have the cli commands to do that ?

[fl0zan0]

found that https://github.com/iNavFlight/inav/blob/master/docs/Board%20-%20MatekF405.md now it works with nav 1.9.1

[stale[bot]]

This issue / pull request has been automatically marked as stale because it has not had any activity in 60 days. The resources of the INAV team are limited, and so we are asking for your help. This issue / pull request will be closed if no further activity occurs within two weeks.

[stale[bot]]

Automatically closing as inactive.

[HJOGermany]

Can you please make a picture of the wired FC, which resistor is It? I have the same problem with my setup. Radio link is ok. Telemetry not.

The instructions of the Matek Site doesn't work. The rxsr is flashed with the newest FPort Firmware

Thx

[teckel12]

@HJOGermany Are you connecting via soft serial?

[HJOGermany]

No, i connected it like shown on the Matek Site On RX4 is my GPS RX5 the Runcam Split

[teckel12]

@HJOGermany According to this thread, that isn't possible due to a resistor added to the FC. Instead, you need to use soft serial. See the solution in previous posts.

[HJOGermany]

Ok Thank sou Problem is fixed

[nateof8]

Thanks @rhwilr !! After weeks of frustrating troubleshooting, this fix also worked for me! I'm hooked up to TX3 and bypassed the 100 ohm resistor between the TX3 pad and the STM32. Thanks a ton!!!

[agetommy]

To bypass the 100ohm resistor on the TX3 pin (C10) for softserial 11 want work in my environment (R-XSR on the designated S.Port connector). A swap to the TX4 pin is the soloution in my case.