From 882f4d2d63272abce8c1966983aa10178e2e971f Mon Sep 17 00:00:00 2001 From: Alberto Bursi Date: Mon, 28 Nov 2016 20:28:12 +0100 Subject: docs: deleting docs because they are obsolete the docs in /docs folder are pretty much obsolete and in a not very friendly format (latex, that requires to be compiled), leaving them there only causes confusion. LEDE documentation's place is the wiki, or the site. Signed-off-by: Alberto Bursi --- docs/debugging.tex | 61 ------------------------------------------------------ 1 file changed, 61 deletions(-) delete mode 100644 docs/debugging.tex (limited to 'docs/debugging.tex') diff --git a/docs/debugging.tex b/docs/debugging.tex deleted file mode 100644 index 2d2a5d3909..0000000000 --- a/docs/debugging.tex +++ /dev/null @@ -1,61 +0,0 @@ -Debugging hardware can be tricky especially when doing kernel and drivers -development. It might become handy for you to add serial console to your -device as well as using JTAG to debug your code. - -\subsection{Adding a serial port} - -Most routers come with an UART integrated into the System-on-chip -and its pins are routed on the Printed Circuit Board to allow -debugging, firmware replacement or serial device connection (like -modems). - -Finding an UART on a router is fairly easy since it only needs at -least 4 signals (without modem signaling) to work : VCC, GND, TX and -RX. Since your router is very likely to have its I/O pins working at -3.3V (TTL level), you will need a level shifter such as a Maxim MAX232 -to change the level from 3.3V to your computer level which is usually -at 12V. - -To find out the serial console pins on the PCB, you will be looking -for a populated or unpopulated 4-pin header, which can be far from -the SoC (signals are relatively slow) and usually with tracks on -the top or bottom layer of the PCB, and connected to the TX and RX. - -Once found, you can easily check where is GND, which is connected to -the same ground layer than the power connector. VCC should be fixed -at 3.3V and connected to the supply layer, TX is also at 3.3V level -but using a multimeter as an ohm-meter and showing an infinite -value between TX and VCC pins will tell you about them being different -signals (or not). RX and GND are by default at 0V, so using the same -technique you can determine the remaining pins like this. - -If you do not have a multimeter a simple trick that usually works is -using a speaker or a LED to determine the 3.3V signals. Additionnaly -most PCB designer will draw a square pad to indicate ping number 1. - -Once found, just interface your level shifter with the device and the -serial port on the PC on the other side. Most common baudrates for the -off-the-shelf devices are 9600, 38400 and 115200 with 8-bits data, no -parity, 1-bit stop. - -\subsection{JTAG} - -JTAG stands for Joint Test Action Group, which is an IEEE workgroup -defining an electrical interface for integrated circuit testing and -programming. - -There is usually a JTAG automate integrated into your System-on-Chip -or CPU which allows an external software, controlling the JTAG adapter -to make it perform commands like reads and writes at arbitray locations. -Additionnaly it can be useful to recover your devices if you erased the -bootloader resident on the flash. - -Different CPUs have different automates behavior and reset sequence, -most likely you will find ARM and MIPS CPUs, both having their standard -to allow controlling the CPU behavior using JTAG. - -Finding JTAG connector on a PCB can be a little easier than finding the -UART since most vendors leave those headers unpopulated after production. -JTAG connectors are usually 12, 14, or 20-pins headers with one side of -the connector having some signals at 3.3V and the other side being -connected to GND. -- cgit v1.2.3