I’ve been looking at the code for sending Miis to the remote and I discovered it’s not as simple as receiving a Mii. You can request a single Mii, but you can’t send only a single Mii – you need to send the entire block of 10 Miis with the properly calculated CRC. That means I need to read all of the Miis, overwrite the one I want to send, calculate the CRC and send either only that one Mii + the CRC or the entire block.
I really love MiiTransferX! I've been using it tonight to make desktops of my Miis for my friends. Thank you so much!
Read all of the data. Set the bytes in the mii data for the new mii in the correct slot. Set the parade bit. Calculate the CRC. Then send the mii for the slot. Then send the parade bytes. Finally send the CRC. I know it is not much simpler, but you only send the crc, parade, and single slot this way. Don't forget about the parade bit.