# Accidental AT+KUSBCOMP=1 lock on custom HL7812 board without physical USB lines **URL:** \ **Category:** HL78\ **Created:** [July 23, 2026, 10:18am UTC](https://forum.sierrawireless.com/t/accidental-at-kusbcomp-1-lock-on-custom-hl7812-board-without-physical-usb-lines/35947 "2026-07-23T10:18:13Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![zsen](https://avatars.discourse-cdn.com/v4/letter/z/b487fb/32.png) [@zsen](https://forum.sierrawireless.com/u/zsen)\ **Post date:** [July 23, 2026, 10:18am UTC](https://forum.sierrawireless.com/t/accidental-at-kusbcomp-1-lock-on-custom-hl7812-board-without-physical-usb-lines/35947/1 "2026-07-23T10:18:13Z")
I made a mistake and ran `AT+KUSBCOMP=1` on an HL7812 module mounted on a custom PCB. Unfortunately, this specific board layout does not break out the physical USB interface to an external port, completely locking me out of standard AT command access over UART1. Here is what I have tried so far: 1. **Flashing via UART0:** I am still able to successfully flash the module firmware via the low-level UART0 bootloader interface. 2. **AT commands:** Runtime AT commands do not work over UART0, so I cannot manually issue `AT+KUSBCOMP=0`. 3. **The Problem:** The standard firmware update process over UART0 leaves the application NV parameter space intact. Therefore, when the modem reboots after the flash, it still prioritizes the missing USB stack, keeping UART1 dead. Since I have functioning bootloader access via UART0, is there a specific command-line argument, parameter flag, or Python script modification I can use during the flash process to forcibly wipe/reset the NVM partition or restore factory defaults? UART0 output: ```auto NOR boot spl: Uncompressing u-boot image ... OK (141488 => 254824 55%) Transferring control to u-boot ... NOR boot spl: Uncompressing u-boot image ... OK (141488 => 254824 55%) Transferring control to u-boot ... U-Boot 2012.10 (Dec 15 2021 - 12:47:40) ALT1250_03_02_00_12_15041_UB Board: ALT1250 Ver: 0.32-SB-E0 (PMP CPU Speed 120 MHz) Platform id 9D9-989 DRAM: 3 MiB Now running in RAM - U-Boot at: 902a4000 Boot mode 2 Flash Manufacturer/Device ID is: 0x20bb18 Enable QUAD mode Flash: 16 MiB *** Warning - Merge environment, using default environment map import OK USB CTRL has been successfully initialized! In: usbtty Out: usbtty Err: usbtty Configuring Flash Write Protection (offset 0x192e00) new_ce_val = 0x3a0001f8 Rst info: shutdown : power on, no reset Hit any key to stop autoboot: 0 Version: 2.0 Nothing to upgrade... hbsb ok. 200 ms ## Starting ``` When I hit a button: ```auto NOR boot spl: Uncompressing u-boot image ... OK (141488 => 254824 55%) Transferring control to u-boot ... NOR boot spl: Uncompressing u-boot image ... OK (141488 => 254824 55%) Transferring control to u-boot ... U-Boot 2012.10 (Dec 15 2021 - 12:47:40) ALT1250_03_02_00_12_15041_UB Board: ALT1250 Ver: 0.32-SB-E0 (PMP CPU Speed 120 MHz) Platform id 9D9-989 DRAM: 3 MiB Now running in RAM - U-Boot at: 902a4000 Boot mode 2 Flash Manufacturer/Device ID is: 0x20bb18 Enable QUAD mode Flash: 16 MiB *** Warning - Merge environment, using default environment map import OK USB CTRL has been successfully initialized! In: usbtty Out: usbtty Err: usbtty Configuring Flash Write Protection (offset 0x192e00) new_ce_val = 0x3a0001f8 Rst info: shutdown : power on, no reset Hit any key to stop autoboot: 0 # # ``` Thanks in advance. ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [July 23, 2026, 10:35am UTC](https://forum.sierrawireless.com/t/accidental-at-kusbcomp-1-lock-on-custom-hl7812-board-without-physical-usb-lines/35947/2 "2026-07-23T10:35:05Z")
Have yoy contacted distributor? To enter AT command in uart0, you need to set at!switracemode to RnD mode or AT mode first > [@Using two UARTS setup for HL78xx, where one UART is used AT commands and a second for PPP traffic](https://forum.sierrawireless.com/t/using-two-uarts-setup-for-hl78xx-where-one-uart-is-used-at-commands-and-a-second-for-ppp-traffic/35298/9): > > How about setting like this? I can use both UART as AT port: ati3 HL7812.5.7.3.0 OK at!entercnd="A710" OK at+Switracemode? +SWITRACEMODE: RnD,9,2,0 OK AT+SWITRACEMODE=AT OK at+cfun=1,1 OK