#U boot raspberry pi drivers#
#U boot raspberry pi driver#

This changes some of the pins exposed on the GPIO header to their 'Alt4' modes. Edit your config.txt and add the following line: enable_jtag_gpio=1 Configuring the Pi Exposing JTAG Linesīefore we begin wiring, let's first set the Raspberry Pi up to expose the CPU's JTAG lines on the 40-pin expansion header. In addition, I'll be using OpenOCD and GDB in order to drive the JTAG debugger from a Linux workstation. I hadn't really had an excuse to break it out until now, so it is what I am using in the rest of the article, but any JTAG debugger should work.

Fiddle the program counter register to enforce a jump instruction to the newly-loaded U-Boot imageĮarlier this year, I thought I'd try the Bus Blaster v3 from Dangerous Prototypes, a simple USB-based JTAG debugger.

Load a U-Boot image into the target's RAM.

Using JTAG from an external workstation targeting the embedded board, it is entirely possible to: It turns out JTAG is the perfect solution to this problem. The code and OpenOCD configuration used in this article are kept in this git repo should you want to follow along.

If only there was a way of squirting a fresh build of U-Boot straight into the board's RAM and booting from there, removing the need for SD cards to be stressed by flash writes and insertion/removal cycles. Re-flashing the SD card with a fresh build of U-Boot.

#U boot raspberry pi drivers#

This is fine for users of stable builds, but when it comes time to start customising configurations, or worse yet, developing drivers for the bootloader, it becomes tedious to repeat the process of: Traditionally, U-Boot can be run on a Raspberry Pi by loading a suitable build of it to the SD card and adjusting the kernel parameter in config.txt.

#U boot raspberry pi driver#

I found myself needing to do so in order to more quickly iterate on changes to driver code I am developing. Also, this article won't cover the configuration of a U-Boot build itself, since there is already a defconfig for the Raspberry Pis. I should preface this with a note that JTAG isn't required to get U-Boot running on any of the Raspberry Pi boards. Written: Loading U-Boot into a Pi with JTAG Making development/iteration faster