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// Converts firmware files from BIN to UF2 format before flashing.
//
// For more information about the UF2 firmware file format, please see:
// https://github.com/Microsoft/uf2
//
//
package main
import (
"bytes"
"encoding/binary"
"io/ioutil"
)
// ConvertELFFileToUF2File converts an ELF file to a UF2 file.
func ConvertELFFileToUF2File(infile, outfile string) error {
// Read the .text segment.
_, data, err := ExtractROM(infile)
if err != nil {
return err
}
output, _ := ConvertBinToUF2(data)
return ioutil.WriteFile(outfile, output, 0644)
}
// ConvertBinToUF2 converts the binary bytes in input to UF2 formatted data.
func ConvertBinToUF2(input []byte) ([]byte, int) {
blocks := split(input, 256)
output := make([]byte, 0)
bl := NewUF2Block()
bl.SetNumBlocks(len(blocks))
for i := 0; i < len(blocks); i++ {
bl.SetBlockNo(i)
bl.SetData(blocks[i])
output = append(output, bl.Bytes()...)
bl.IncrementAddress(bl.payloadSize)
}
return output, len(blocks)
}
const (
uf2MagicStart0 = 0x0A324655 // "UF2\n"
uf2MagicStart1 = 0x9E5D5157 // Randomly selected
uf2MagicEnd = 0x0AB16F30 // Ditto
uf2StartAddress = 0x2000
)
// UF2Block is the structure used for each UF2 code block sent to device.
type UF2Block struct {
magicStart0 uint32
magicStart1 uint32
flags uint32
targetAddr uint32
payloadSize uint32
blockNo uint32
numBlocks uint32
familyID uint32
data []uint8
magicEnd uint32
}
// NewUF2Block returns a new UF2Block struct that has been correctly populated
func NewUF2Block() *UF2Block {
return &UF2Block{magicStart0: uf2MagicStart0,
magicStart1: uf2MagicStart1,
magicEnd: uf2MagicEnd,
targetAddr: uf2StartAddress,
flags: 0x0,
familyID: 0x0,
payloadSize: 256,
data: make([]byte, 476),
}
}
// Bytes converts the UF2Block to a slice of bytes that can be written to file.
func (b *UF2Block) Bytes() []byte {
buf := bytes.NewBuffer(make([]byte, 0, 512))
binary.Write(buf, binary.LittleEndian, b.magicStart0)
binary.Write(buf, binary.LittleEndian, b.magicStart1)
binary.Write(buf, binary.LittleEndian, b.flags)
binary.Write(buf, binary.LittleEndian, b.targetAddr)
binary.Write(buf, binary.LittleEndian, b.payloadSize)
binary.Write(buf, binary.LittleEndian, b.blockNo)
binary.Write(buf, binary.LittleEndian, b.numBlocks)
binary.Write(buf, binary.LittleEndian, b.familyID)
binary.Write(buf, binary.LittleEndian, b.data)
binary.Write(buf, binary.LittleEndian, b.magicEnd)
return buf.Bytes()
}
// IncrementAddress moves the target address pointer forward by count bytes.
func (b *UF2Block) IncrementAddress(count uint32) {
b.targetAddr += b.payloadSize
}
// SetData sets the data to be used for the current block.
func (b *UF2Block) SetData(d []byte) {
b.data = make([]byte, 476)
copy(b.data[:], d)
}
// SetBlockNo sets the current block number to be used.
func (b *UF2Block) SetBlockNo(bn int) {
b.blockNo = uint32(bn)
}
// SetNumBlocks sets the total number of blocks for this UF2 file.
func (b *UF2Block) SetNumBlocks(total int) {
b.numBlocks = uint32(total)
}
// split splits a slice of bytes into a slice of byte slices of a specific size limit.
func split(input []byte, limit int) [][]byte {
var block []byte
output := make([][]byte, 0, len(input)/limit+1)
for len(input) >= limit {
block, input = input[:limit], input[limit:]
output = append(output, block)
}
if len(input) > 0 {
output = append(output, input[:len(input)])
}
return output
}
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