From 007136a010c4d620d381532914e0d0b60eb79b72 Mon Sep 17 00:00:00 2001 From: Leah Rowe Date: Sun, 29 Dec 2024 15:12:25 +0000 Subject: [PATCH] thoUART t480 Signed-off-by: Leah Rowe --- site/docs/install/t480.md | 41 +++++++++++++-------------------------- 1 file changed, 14 insertions(+), 27 deletions(-) diff --git a/site/docs/install/t480.md b/site/docs/install/t480.md index 48a8880..d079828 100644 --- a/site/docs/install/t480.md +++ b/site/docs/install/t480.md @@ -356,40 +356,27 @@ the Fn keys for it don't currently work, as of 6 December 2024. You can set the backlight manually, or use a hotkey, depending on your window manager or desktop environment. -UART +UART (T480 only. Not T480S) ---- -To our knowledge, this functionality is *only* available in coreboot-based -firmware such as Libreboot. It is completely unsupported on the original -firmware! +**NOT supported on the S model (T480s). Please only do it on a T480.** -A serial console is possible via the line-out (headphone jack). Not yet tested -on the T480s (S model), nor implemented, but it is working on the regular -T480 (non-S model). +The EC on ThinkPad T480 has a UART available, and it is enabled in coreboot, +as used by Libreboot. However, you must use a *specific* EC firmware version. +Please read notes elsewhere in this page regarding Lenovo UEFI/EC BIOS updates; +an exact version number is referenced, which you must install prior to Libreboot +installation. -**TODO: show photo and wiring diagram here.** +Ways to flash the EC firmware from Libreboot have not yet been established. Now, +please observe the following photo: -Use baud rate 115200 in your favourite serial terminal client, e.g. GNU Screen. +ThinkPad T480 UART jumpers -Next to the headphone jack on the T480, you will find pads for two 0ohm jumpers, -normally unpopulated, but you can bridge each jumper yourself using a 0ohm 0201 -jumper; alternatively, simply strip a bit a wire (30awg solid core) and carefully -solder the wire across each of the pad jumpers, then carefully using a pair -of side cutters to cut off the excess wire, being careful not to rip the pads! +You will solder zero-ohm jumps on the indicated footprints. These correspond +to TX and RX, which are connected to the R and L lines on the headphone jack, +respectively; a ground will also be available. -If you do this, please make sure to have the latest EC firmware as of 5 -December 2024 (do not use older than what was latest on this day, and don't -use newer versions), because the code for this in coreboot targets a specific -area of code within the EC firmware. - -You can then wire a 3.5mm stereo plug. On the other end you will wire your -TX/RX lines as you wish, to a suitable UART adapter; any 3.3v-rated TTL -adapter should work. The Raspberry Pi Pico can be used for this, which is handy -because that can also be used as a serprog-based NOR flasher! - -The T480s (S model) schematics is a bit different and the signals are -properly muxed. Note that this is not to be confused with `spkmodem`, which -has not been tested on these boards (but could theoretically be possible too). +You can hook this up to any 3.3v TTL UART dongle, to get a serial console. Idea for 2nd NVMe mod ----------------------