Unable to change VDD to 1.8V

Question

Dear all 
 I am currently working with a nRF52840 Dongle, the ble_app_blinky_s140 example. 
 To power some external circuits i have to set VDD to 1.8V. 
 Until now i tried the following approaches. 
 https://devzone.nordicsemi.com/f/nordic-q-a/20528/why-data-can-not-be-wrote-into-the-registers-of-nrf52840/80038#80038 
 by adding this two lines to the uicr_config.h 
 const uint32_t UICR_ADDR_EXTSUPPLY __attribute__((at(0x10001300))) __attribute__((used)) = 0xFFFFFFFF;//Enabled
const uint32_t UICR_ADDR_REGOUT0 __attribute__((at(0x10001304))) __attribute__((used)) = 0xFFFFFFF5;//3.3V 
 
 The second approach was to change the GPIO_OUTPUT_VOLTAGE_SETUP Function to 1.8V 
 None of these changed the Output Voltage. 
 Any idea why this doesn't work? 
 Regards 
 Marcel

michel_93 · Accepted Answer

Hi, I have found a solution for this problem by adding the following functions to the main of the blinky example. /** * @brief Function to erase UICR Registers. */ void nvmcErase(void) if (NRF_UICR->REGOUT0 != UICR_REGOUT0_VOUT_1V8) { NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Een << NVMC_CONFIG_WEN_Pos; //erase enable while (NRF_NVMC->READY == NVMC_READY_READY_Busy){} NRF_NVMC->ERASEUICR = NVMC_ERASEUICR_ERASEUICR_Erase << NVMC_ERASEUICR_ERASEUICR_Pos; //erase UICR while (NRF_NVMC->READY == NVMC_READY_READY_Busy){} NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Ren << NVMC_CONFIG_WEN_Pos; //read only enable while (NRF_NVMC->READY == NVMC_READY_READY_Busy){} } } /** * @brief Function for configuration of REGOUT0 register. */ void vddInit(void) { if (NRF_UICR->REGOUT0 != UICR_REGOUT0_VOUT_1V8) { NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Wen << NVMC_CONFIG_WEN_Pos; //write enable while (NRF_NVMC->READY == NVMC_READY_READY_Busy){} NRF_UICR->REGOUT0 = UICR_REGOUT0_VOUT_1V8; //configurate REGOUT0 NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Ren << NVMC_CONFIG_WEN_Pos; while (NRF_NVMC->READY == NVMC_READY_READY_Busy){} NVIC_SystemReset(); // Reset device } } The first function is to clear the UICR Registers. The second one then writes the UICR with the new values. Keep in mind to delete or uncomment the bsp_board_leds_init function in the boards.c file if you use a dongle. Also the LEDs will not work properly if you use the dongle with 1.8V. Regards, Michel

Unable to change VDD to 1.8V

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