N4-board BT - no connection ?

[Crizz]

I almost finished my M4-setup, but have trouble with the N4-expander. BT is paired with my smartphone, but when i want to connect to GCS-App, it disconects after 3 - 4 seconds. So guess there is a problem on the board, maybe solderwork.

Can i use the UART1-connector to check if i can connect to the module by serial monitor / PC ? Must i disconnect the N4 from the M4 FCU ? Or any other suggerstion how to check the problem ?

[Crizz]

I tried several things, but unfortuneately i dont have a connector fits to the UART1-socket. So i couldnt try with modem-software if the MC05 responds to AT-commands. I even resoldered the module to the N4 Expander (Hotair), but no changes.

What is strange :

When i power up the unit, red LED is flashing rapidly (3-4 times/second) - means device not paired as fas as i recall. I paired it with my smartphone, red LED turns to slow blinkling ( 1 time/second). Shouldnt it stay solid ??

And : when i re-power the system, LED ist flashing rapidly again- i need to unpair and pair again.

I figured that on my M4-board, a reistor seems missing (R26 - see attached pic). Can anybody say more about it and if this could cause my BT-problem ?

[Crizz]

I kept searching and figured the following :

1.) there is no connection between the Tx / Rx pads of the BT-module and the UART1-connector - only Gnd and 3.3 V can be verified

2.) there is a resistor missing (R3) on the Epxansionboard

Thsi is very strange - why do they leave components untipped without any information about ? So nobody knows if this is a tipping-fault or left blank intentionally.

I guess i will remove the UART-header and solder wires for external BT-module to the module to check if this runs. But to be honest, this should be checked by developer of the N4 Expander, maybe there is a design fault in the v1.1 layout or bad batch from PCBa manufacturer.

[JussiH]

R3 is not to be mounted. Its part of a Voltage divider circuit that is for use only with Early M4 boards

The N4 boards are tested before beeing shipped, so it should work. I will cover problematic boards under warranty, but you need to send it back here for testing and troubleshooting - send me a PM.

[aBUGSworstnightmare]

[Crizz]

thanks for information !!

But, figured the N4 Expander is bad - no connection between Rx on UART-connector to Expansionport , and no connection between Rx and Tx from BT-module to Expansionport. So there must be either fault in production or layout. Guess i call Paul from Flyduino to check this.