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Documentation is now handled by the same processes we use for code: Add something to the Documentation/ directory in the coreboot repo, and it will be rendered to https://doc.coreboot.org/. Contributions welcome!
This page describes a tester device, which is capable of programming a BIOS ROM chip while it is connected to a live mainboard. The tester is controlled by a host PC via USB. The purpose of this tester device is to provide a do-it-yourself hardware for testing Coreboot builds. The goal is to support automated builds and tests from version control repository.
The tester is built around the Atmel AT90USB162 microcontroller, which is programmed using avr-gcc and the LUFA library. The host-side software is currently Flashrom.
- Tester consists of two circuit boards: main and auxiliary board. Main tester board connects to host via USB, and to aux board via ribbon cable.
- Optionally, the main tester board can be connected to the reset and ATX power pins of the target mainboard. All common sense voltages (1..5V) are supported.
- The main tester board has a standard serial port for reading debug output from the target mainbaord.
- PCB layout is kept simple, so that it can be built using hobbyist methods, e.g. toner transfer PCB etching. The parts have been chosen so that they should be quite well available and inexpensive.
- Designed using open source tools.
- Currently supports SPI ROMs only.
- Current firmware and flashrom extension do not support serial port or reset/power switch operation.
In the images shown are two-sides circuit boards. Red mask shows component-side copper and blue mask shows solder-side copper.
- R1,R2: USB line termination resistors. 22 ohm.
- R3,R4: LED current limiters. 270 ohm.
- R5,R6,R7: Pull-ups. 10k ohm.
- C1,C2: Oscillator capacitors. 22 pF.
- U2: Crystal oscillator. 16 MHz.
- C3,C4,C5,C6: Charge pump capacitors. About 100 nF.
- C7: Power bypass. Used 1 microF.
- J1: 2x5 pin header. Pins 1-6 are used to load AVR firmware. Pins 1-6,9,10 connect to aux PCB.
- J2: Alternative connector for RS232.
- CONN4: 2x2 pin header
- CONN2: USB B (device-side) connector.
- CONN3: DB-9 male connector with 90° angle.
- U1: Atmel AT90USB162 in TQFP-32.
- U3: Texas Instruments MAX3232ECDG4 in SOIC-16.
- U4: Texas Instruments SN74CBT3306D Dual FET bus switch in SOIC-8.
- D1,D2: LEDs. Used green and yellow.
- U1: DIP-8 socket for SPI ROM chip.
- U2: SOIC-16 Texas Instruments SN74CBTLV3257D FET Multiplexer
- U3: DIP-8 pin header on the solder-side of the board (plugs to mainboard ROM socket)
- C1,C2: Power bypass capacitors. 100nF worked fine.
- D1,D2: Schottky diodes with low forward voltage drop. Here SD103A-T/R
- R1: Pull-up resistor. 120 kohm was used.
- J1: 2x5 pin header for connecting to tester main PCB. Pins 7 and 8 are not used.