User Tools

Site Tools


inbox:mikrotik:mikrotik_rb750gr3
This wiki is read only and for archival purposes only. >>>>>>>>>> Please use the new OpenWrt wiki at https://openwrt.org/ <<<<<<<<<<

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
inbox:mikrotik:mikrotik_rb750gr3 [2017/12/27 01:57]
semicuda [Serial]
inbox:mikrotik:mikrotik_rb750gr3 [2018/01/08 17:02] (current)
sidepipe [Flashing the image to the chip] Info on the on-board SPI header
Line 130: Line 130:
   ​   ​
 **Warning** Make sure to make a backup of the flash chips contents before flashing the image you constructed! This way, if something goes wrong, you can try flashing the stock image again. **Warning** Make sure to make a backup of the flash chips contents before flashing the image you constructed! This way, if something goes wrong, you can try flashing the stock image again.
 +
 +There is an unoccupied pin header on the PCB of the 750Gr3 which can be used to write the flash without having to de-solder it from the board. The pinout of this header is:
 +
 +^ Header Pin ^ Purpose ^
 +| 1 | CLK |
 +| 2,10 | GND |
 +| 3 | DO |
 +| 4 | VCC |
 +| 5 | CS |
 +| 6,7 | Not Connected |
 +| 8 | Program ( see note below ) |
 +| 9 | DI |
 +
 +When programming the flash chip, pin 8 should be tied to GND. This freezes operation of the SoC so that it doesn'​t interfere with the programming process. You should also NOT connect VCC to the programmer, instead power the 750gr3 using its normal power supply. This removes the possibility of overloading the USB/​Programmer supply.
 +
 +Although the original author of this section used a Bus Pirate, you can obtain CH341A type USB EEPROM programmer for very little money. There are several advantages to this, one of which being that the programmer has a 16 pin EEPROM socket on board, so you can simply wire the header of the 750gr3 to a DIL socket and plug it in. If you do this, you should wire the pins as follows:
 +
 +^ 750Gr3 Header Pin ^ DIL pin ^
 +| 1 | 10 |
 +| 2 | 1 |
 +| 3 | 6 |
 +| 5 | 5 |
 +| 8 | 8 |
 +| 9 | 9 |
 +
 +All other pins should remain disconnected. To be safe, you should first plug the DIL into the programmer - this connects pin 8 of the header to GND and prevents the 750 booting up. Then, power on the 750. Then plug the programmer into the USB. It probably doesn'​t matter, but this order prevents any signals being applied to the flash chip before the chip itself is powered.
   ​   ​
 The exact procedure for flashing the image to the W25Q128FV flash chip depends on your flasher. In this example, I used a bus pirate with flashrom. The connections and commands follow this guide: [[https://​www.flashrom.org/​Bus_Pirate]]. Using the bus pirate, reading and writing to the chip can take a very long time! The exact procedure for flashing the image to the W25Q128FV flash chip depends on your flasher. In this example, I used a bus pirate with flashrom. The connections and commands follow this guide: [[https://​www.flashrom.org/​Bus_Pirate]]. Using the bus pirate, reading and writing to the chip can take a very long time!
inbox/mikrotik/mikrotik_rb750gr3.txt · Last modified: 2018/01/08 17:02 by sidepipe