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Transactions with the Coldcard hardware wallet

Cold Card

Recently I had to move the BTCs from the Coldcard hardware wallet to another destination, for this I had several options, one was to import the seed and passphrase it into another wallet such as Wasabi or Electrum as indicated in this post “Import verification of Coldcard seed and passphrase at Electrum and Wasabi” but in the end I preferred to send them using the transaction  PSBT (Partially Signed Bitcoin Transactions) that allows the operation of the shipment while maintaining the private keys off-line, that is, without being exposed to the Internet in no time.

In the Coldcard

  • Enter the two pins and make sure you have inserted the passphrase and applied it (APPLY) it is interesting to check the master key fingerprint
  • Export the file with the xPub (new-wallet.json)

MicroSD → Export Wallet → Electrum wallet → Native Segwit

In Electrum

  • Enter the MicroSD of the Coldcard
  • Import the file with the public master key. Open an Electrum wallet and load the file new-wallet.json 

File → Open → File      

  • Generate the PSTB transaction. 

In the Address tab choose the source address right mouse button → Spen from 

  • Save the generated psbt file to the microSD card

In the Coldcard

  • Make sure you have inserted the passphrase and applied it (APPLY) 
  • Enter the microSD with the file with the transaction PSBT
  • Sign the transaction

Ready to sign -> “Ok to send?” 

In Electrum

  • Enter the microSD with the signed PSBT transaction

Tools -> Load transaction -> from file

  • In the Send tab indicate the address that will receive the bitcoins and send
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BCubium hardware

BCubium Board


  • CPU: Allwinner H5,Quad-core 64-bit high-performance Cortex A53
  • DDR3 RAM:1GB
  • Storage: 8GB eMMC
  • Network: Gbps Ethernet
  • WiFi: 802.11b/g/n
  • Bluetooth: 4.0 dual mode
  • USB Host: 2 x Independent USB Host
  • MicroSD Slot: 1 x Slot. It supports system booting or is used to hold a storage card
  • Audio Input/Output: 4-Pin, 2.54mm pitch pin-header
  • MicroUSB: power input
  • Debug Serial: 4Pin, 2.54mm pitch pin-header
  • GPIO1:24Pin, 2.54mm pitch double-row pin-header containing UART, SPI, I2C and IO
  • GPIO2:12Pin, 2.54mm pitch pin-header containing USB, IR receiver,I2S and IO
  • Power Supply: DC 5V/2A
  • PCB Dimension: 40 x 52mm
  • PCB Layer: 6-Layer


  • BCubium Box 
  • Motherboard NanoPi NEO Plus2
  • 500GB microSSD
  • Power supply (with worldwide connectors)
  • Network Cable