Hyperload Protocol

From Embedded Systems Learning Academy
Jump to: navigation, search


Hyperload is a program based off of UART to program a CPU at a very high speed. Typically, this is 10-20 times faster than using other flash programming programs such as FlashMagic. This is a good way to write your own bootloader for your own CPU. It is recommended to test your bootloader by not doing any real programming and once you are past the protocol, then add your code to perform real flash programming within your CPU.

Hyperload Protocol

The Hyperload protocol is derived from the original "Megaload" program

Protocol Phase 1 : Handshake

  1. Upon bootup, initialize your UART at either 4800, 9600, 19200 or 38400bps
  2. Send 0xFF over UART
    Regardless of your speed, Hyperload will detect your baud rate and send 0x55 back to you.
    When you receive 0x55, it is an indication that Hyperload is present
  3. Send 0xAA back over UART
  4. Hyperload will now send a baud rate control word to switch over to high speed mode.
    This control word is based on the following formula and the speed of CPU set @ Hyperload itself:
    Baud Rate = (CPU Speed / (Control Word + 1)) / 16
    Note that this control word dictates future speed, so if you want to continue at your original baud rate, be sure to choose that speed @ Hyperload COM Port speed.
  5. Echo back the Control Word Hyperload sent while maintaining original baud rate
  6. Switch over to the new baud rate or optionally if Hyperload COM Port speed is chosen as your original baud rate, disregard this control word.

Protocol Phase 2 : Block size Setup & Bootloader Blocks

  1. Send a CPU description string to Hyperload:
    $CPU Name:Block Size:Boot Size in Words:Flash Size in Kilobytes
    Example: "$LPC1758:4096:2048:512\n"
    This means your block(chunk) size is 4096 bytes, your bootloader size is 2048*2 bytes, and your flash size is 512Kbytes
    The block size is the chunks Hyperload will now send out of the HEX Programming file in "One shot"
  2. Send Hyperload "OK" Character: "!" to continue
  3. Hyperload will now send you empty blocks which span the size of your bootloader
    Each block will contain 2 byte block number, and also contain 1 byte checksum (see Phase 3 below)
    Send Hyperload_OK for each block for this dummy bootloader blocks

Protocol Phase 3 : The Flash Program Blocks

  1. Based on your block size, hyperload will now send you block numbers followed by programming file contents (.Hex file)
    • Hyperload will send you 16-bit block number, MSB first
    Hyperload will now send you the chunk of programming data, 4096 bytes according to the CPU description string above.
    Hyperload will now send you 1 byte checksum of the programming chunk:
    Checksum is simply all the programming bytes added up
  2. Send back your status after you program this chunk in your processor:
    •  ! for OK when checksum passes and you program and verify your flash correctly.
    • @ for checksum validation failure
    • ^ for any other error you experience during programming
    • Note: If ! is not sent, Hyperload will send you previous block again
  3. If ! was received, Hyperload will send you the rest of the chunks
  4. When no more chunks remain in your .Hex file, Hyperload will send you 0xFFFF for block number
    At this point, send back "*" finish character and jump to your application code.

Sample Code

int main(void)
	int blockNumber = 0;
	uart0Getchar(100);  // Flushes UART and also provides delay of 100ms
	uart0Putchar(0xff); // Send 0xFF for Hyperload to sync with our baud rate
	// Hyperload will send 0x55 to notify that it is alive!
	if (0x55 == uart0Getchar(500))
		// Notify Hyperload that we're alive too!

		char baudRateControlWord = uart0Getchar(500); // Get new baud rate control word
		uart0Putchar(baudRateControlWord);		      // Echo it back to verify

		 * Hyperload Frequency should be set to 48,000,000 for this to work correctly
		 * It calculates the baud rate by: 48Mhz/(16*BAUD) - 1 = CW (control word)
		 * So we solve for BAUD:  BAUD = (48/(CW + 1))/16
		long baudRate = (48000000UL/(baudRateControlWord+1))/16;

		// Send our CPU information along with data parameters:
		// Name:Blocksize:Bootsize/2:FlashSize

		uart0Putchar(HYPERLOAD_OK); // Now start programming...
			blockNumber = (((int) uart0Getchar(500) & 0xff) << 8) | (uart0Getchar(100) & 0xff);

			if(0xffff == blockNumber) {
			else {
			    // Get 1 block + checksum and program this block number

	delay_ms(5); // Need this to finish sending previous char.

	// Jump to application code
	uart0Puts("\nBooting Application . . .");
	return 0;


Uart Get Char Delay

Implement a getchar() that times out after 300-1000 milliseconds, if you don't receive anything when you expect, start your application code or restart the entire bootloader process.

High Speed Mode

High Speed Mode and baud rate switch is present to start handshake at a default rate and switch to an optional high speed COM port rate if the device supports it. Since this is configurable in Hyperload, you can OPTIONALLY take advantage of this.

Why send dummy bootloader blocks?

In a CPU like NXP, your bootloader lives at first 4K or so, and the programming .Hex file you want to program lives at an offset of 4K from the flash location 0x000.0000 Taking this in account, Hyperload sends the first 4K of data regardless and this leaves the protocol with more flexibility. Since it is hard to change this standard without breaking the protocol and existing compiled program, the best option is simply to ignore this first chunk of data.