# Can't get LimeSDR to work: Tx Calibration: MCU error 5

**URL:** <https://discourse.myriadrf.org/t/cant-get-limesdr-to-work-tx-calibration-mcu-error-5/2829>\
**Category:** LimeSDR\
**Created:** [17 May 2018 17:08 UTC](https://discourse.myriadrf.org/t/cant-get-limesdr-to-work-tx-calibration-mcu-error-5/2829 "2018-05-17T17:08:26Z")\
**Posts on this page:** 11\
**Page:** 1

<div class="post-metadata">

**Author:** ![AleksK](https://avatars.discourse-cdn.com/v4/letter/a/b487fb/32.png) [@AleksK](https://discourse.myriadrf.org/u/AleksK)\
**Post date:** [17 May 2018 17:08 UTC](https://discourse.myriadrf.org/t/cant-get-limesdr-to-work-tx-calibration-mcu-error-5/2829/1 "2018-05-17T17:08:26Z")

</div>

I’m having a problem with my new LimeSDR boards. I am trying to run the LoRa example from here:  
[LoRa modem with LimeSDR – MyriadRF](https://myriadrf.org/blog/lora-modem-limesdr/)

and I get the hollowing output:

> [15:34:42.655221] PothosFlow.MainWindow: Welcome to Pothos v0.6.1-PothosSDR-2018.04.26-vc14-x64  
> [15:34:42.754976] PothosFlow.GraphEditor: Loading C:/Users/ak/Documents/SDR/LoRa-SDR/examples/lora\_sdr\_relay.pothos  
> [15:34:43.140839] PothosFlow.MainWindow: Initialization complete  
> [15:34:44.782000] SoapySDR: Make connection: ‘LimeSDR-USB [USB 3.0] 9070602431B19’  
> [15:34:44.962000] SoapySDR: Reference clock 30.72 MHz  
> [15:34:44.963000] SoapySDR: Device name: LimeSDR-USB  
> [15:34:44.963000] SoapySDR: Reference: 3.072e+07 MHz  
> [15:34:45.342000] SoapySDR: LMS7002M calibration values caching Disable  
> [15:34:46.086000] : [INFO] [UHD] Win32; Microsoft Visual C++ version 14.0; Boost\_106300; UHD\_3.11.0.1-0-ge00f1f37  
> [15:34:53.743000] SoapySDR: Tx Calibration: MCU error 5 (Loopback signal weak: not connected/insufficient gain?)  
> [15:34:53.916000] SoapySDR: Rx calibration finished  
> [15:34:54.629000] SoapySDR: popping from TX, samples popped 0/1020  
> [15:34:55.509000] SoapySDR: popping from TX, samples popped 0/1020  
> [15:34:56.520000] SoapySDR: popping from TX, samples popped 0/1020

If I connect the board to LimeSuite and try ‘Calibrate All’ I get the same error:

> [12:57:04] INFO: Reference clock 30.72 MHz  
> [12:57:04] INFO: Connected Control port: LimeSDR-USB FW:4 HW:4 Protocol:1 GW:2.16 Ref Clk: 30.72 MHz  
> [12:57:08] ERROR: Tx Calibration: MCU error 5 (Loopback signal weak: not connected/insufficient gain?)

If, however I update the firmware from LimeSuite (Modules-\>Programming), reset the module to ‘Default’ configuration, calibration with LimeSuite is successful, but as soon as I try to run the LoRa example, it fails again with the same error, and LimeSuite cannot calibrate until I reprogram the board.

I’m working on Windows 10, x64 if it matters. I tried this on two boards and the results are identical. Any help would be appreciated.

---

<div class="post-metadata">

**Author:** ![ricardas](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/ricardas/32/86_2.png) [@ricardas](https://discourse.myriadrf.org/u/ricardas)\
**Post date:** [17 May 2018 19:10 UTC](https://discourse.myriadrf.org/t/cant-get-limesdr-to-work-tx-calibration-mcu-error-5/2829/2 "2018-05-17T19:10:20Z")

</div>

“insufficient gain”, you need to increase transmitter gain.

---

<div class="post-metadata">

**Author:** ![AleksK](https://avatars.discourse-cdn.com/v4/letter/a/b487fb/32.png) [@AleksK](https://discourse.myriadrf.org/u/AleksK)\
**Post date:** [18 May 2018 15:34 UTC](https://discourse.myriadrf.org/t/cant-get-limesdr-to-work-tx-calibration-mcu-error-5/2829/3 "2018-05-18T15:34:39Z")

</div>

That was it, thank!

---

<div class="post-metadata">

**Author:** ![dast](https://avatars.discourse-cdn.com/v4/letter/d/e56c9b/32.png) [@dast](https://discourse.myriadrf.org/u/dast)\
**Post date:** [11 January 2019 22:02 UTC](https://discourse.myriadrf.org/t/cant-get-limesdr-to-work-tx-calibration-mcu-error-5/2829/4 "2019-01-11T22:02:04Z")

</div>

using good antenna or using power amplifier for the Tx reslove the problem?  
How about the Rx,?

---

<div class="post-metadata">

**Author:** ![ricardas](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/ricardas/32/86_2.png) [@ricardas](https://discourse.myriadrf.org/u/ricardas)\
**Post date:** [11 January 2019 22:20 UTC](https://discourse.myriadrf.org/t/cant-get-limesdr-to-work-tx-calibration-mcu-error-5/2829/5 "2019-01-11T22:20:19Z")

</div>

calibration is done using internal loopback, it does not depend on external elements (antennas, amplifiers…)

---

<div class="post-metadata">

**Author:** ![dast](https://avatars.discourse-cdn.com/v4/letter/d/e56c9b/32.png) [@dast](https://discourse.myriadrf.org/u/dast)\
**Post date:** [12 January 2019 03:35 UTC](https://discourse.myriadrf.org/t/cant-get-limesdr-to-work-tx-calibration-mcu-error-5/2829/6 "2019-01-12T03:35:34Z")

</div>

But you said that i should increase transmitter gain? how to process so if it’s on internal ? That I misunderstand is, where did the loopback obtain the gain.

---

<div class="post-metadata">

**Author:** ![ricardas](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/ricardas/32/86_2.png) [@ricardas](https://discourse.myriadrf.org/u/ricardas)\
**Post date:** [12 January 2019 09:37 UTC](https://discourse.myriadrf.org/t/cant-get-limesdr-to-work-tx-calibration-mcu-error-5/2829/7 "2019-01-12T09:37:04Z")

</div>

You need to increase Tx/Rx gain by changing the chip configuration settings. I have no idea what software you are using, so I can’t tell you exactly how to do it. LimeSuite API has `LMS_SetNormalizedGain` or `LMS_SetGaindB` functions

---

<div class="post-metadata">

**Author:** ![dast](https://avatars.discourse-cdn.com/v4/letter/d/e56c9b/32.png) [@dast](https://discourse.myriadrf.org/u/dast)\
**Post date:** [12 January 2019 18:39 UTC](https://discourse.myriadrf.org/t/cant-get-limesdr-to-work-tx-calibration-mcu-error-5/2829/8 "2019-01-12T18:39:57Z")

</div>

I use limesuite with soapyUHD and it’ appears on it.  
– Make connection: ‘LimeSDR Mini [USB 3.0] 1D3AC779327FE0’

– Reference clock 40.00 MHz

– Device name: LimeSDR-Mini

– Reference: 40 MHz

– LMS7002M calibration values caching Disable  
UHD Error:

Tx Calibration: MCU error 5 (Loopback signal weak: not connected/insufficient gain?)

– Rx calibration finished  
UHD Warning:

popping from TX, samples popped 540/1020

i will send you the version of my limesuite and uhd if you need it and if you have any solution for it?

---

<div class="post-metadata">

**Author:** ![dast](https://avatars.discourse-cdn.com/v4/letter/d/e56c9b/32.png) [@dast](https://discourse.myriadrf.org/u/dast)\
**Post date:** [13 January 2019 16:05 UTC](https://discourse.myriadrf.org/t/cant-get-limesdr-to-work-tx-calibration-mcu-error-5/2829/9 "2019-01-13T16:05:32Z")

</div>

Mine also @ricardas with soapyUHD i have this error : Tx Calibration: MCU error 5 (Loopback signal weak: not connected/insufficient gain? but with limesuite the calibration is fine. i don’t know how to fix it !

---

<div class="post-metadata">

**Author:** ![muratoznn](https://avatars.discourse-cdn.com/v4/letter/m/b782af/32.png) [@muratoznn](https://discourse.myriadrf.org/u/muratoznn)\
**Post date:** [16 May 2019 11:32 UTC](https://discourse.myriadrf.org/t/cant-get-limesdr-to-work-tx-calibration-mcu-error-5/2829/10 "2019-05-16T11:32:57Z")

</div>

I solved This Problem Osmocom set up 2.5 5 mhz on their orginal settings osmo-trx İf you write all of information antenna sampling code vs İt will start . But orginal osmo-trx settings you can not change . İt can be 120 Mhz singal transmitting I have performed now . But dont do 900 Mhz . İn my opion you use limesdr module.

---

<div class="post-metadata">

**Author:** ![muratoznn](https://avatars.discourse-cdn.com/v4/letter/m/b782af/32.png) [@muratoznn](https://discourse.myriadrf.org/u/muratoznn)\
**Post date:** [16 May 2019 11:33 UTC](https://discourse.myriadrf.org/t/cant-get-limesdr-to-work-tx-calibration-mcu-error-5/2829/11 "2019-05-16T11:33:38Z")

</div>

dont Forget İf you dont put Antenna: BAND1 İt can not send signal