docs/guides/lab-assembly/asrock_turind8ud.md: use SPI flash TPM adapters

The host BIOS SPI flash was wired to the TPM header with individual DuPont
cables, which does not work reliably at the SPI clock used for flashing. Use
a pair of SPI flash TPM adapter PCBs instead, one on the motherboard
TPM_BIOS_PH_1 header and one on the SPI extender HAT SPI_1 header, joined by
an FPC cable of around 30 cm. Longer cables may not work.

Also state that both UART output select jumpers, TX and RX, go to RS232 +
COM on J16.

Signed-off-by: Michał Iwanicki <michal.iwanicki@3mdeb.com>

Author: m-iwanicki

docs/guides/lab-assembly/asrock_turind8ud.md

@@ -21,9 +21,14 @@ for the CPU, RAM, case, power supply, and so on.
 - NOUS A1T smart outlet
 - IDC to RS232 adapter
 - RS232 null modem cable
-- DuPont 2.0mm to 2.54mm pitch cables (for the host SPI flash)
-- 3x female to female wire cables
-- 2x5 1.27mm pitch IDC connector to individual 2.54mm female DuPont connector
+- SPI flash TPM adapter set, one for the motherboard `TPM_BIOS_PH_1` header and
+    one for the SPI extender HAT
+- matching IDC or FPC cable around 30 cm long (for the host SPI flash),
+    depending on adapter used in previous point
+    * FPC: pitch 1 mm, 13 conductors, same side contacts
+    * IDC: pitch: 2.54 mm, 14 conductors
+- 3x 2.54 mm female to female jumper wire cables
+- 2x5 1.27mm pitch IDC connector to individual 2.54mm female connector
     cables (for the BMC SPI flash)
 - 3D printed RTE mount (modular base with a stackable RTE base)
 - 4x M3 6mm screws with nuts (to join the 3D printed parts)
@@ -71,9 +76,10 @@ The following sections describe how to enable all of the following features:
 
 ### Serial connection
 
-- Fit the jumpers on the RTE [UART output select
+- Fit both jumpers, the TX one and the RX one, on the RTE [UART output select
     header](../../transparent-validation/rte/v1.1.0/specification.md#uart-output-select-header)
-    to select `RS232 + COM`.
+    (`J16`) to `RS232 + COM`. That routes the serial output to the DB9
+    connector.
 - Connect the IDC to RS232 adapter to the COM1 header on the motherboard.
 
     ![](images/turind8ud_serial.jpg)
@@ -125,16 +131,50 @@ automatically.**
 #### Host boot flash
 
 The host BIOS SPI flash is programmed through the on-board TPM header, which
-exposes the SPI bus. Remove the TPM module and wire the `SPI_1` header to the
-TPM header. For the pinout and detailed wiring, refer to the
-[board's recovery section (setup with RTE)](../../variants/asrock_turind8ud/recovery.md#external-flashing).
+exposes the SPI bus. An SPI flash TPM adapter PCB set carry the bus between the
+motherboard and the RTE, one on the motherboard `TPM_BIOS_PH_1` header and one
+on the SPI extender HAT, joined by a ribbon cable. Do not wire the TPM header
+with individual jumper wires - that wiring does not work reliably at the SPI
+clock used for flashing.
+
+The adapters come in two variants, one with an IDC connector and one with an FPC
+connector:
+
+![](images/turind8ud_tpm_adapters.jpg)
+
+Pick one pair and use it on both ends. The rest of this guide uses the FPC cable:
+
+![](images/turind8ud_tpm_adapter_pair.jpg)
+
+The cable should be around 30 cm - longer cables may not work.
+
+Install the motherboard-side adapter before mounting the board in the case - it
+can also be done with the board already in the case, but it is harder. Install
+the PCB with the `TO MOBO` silkscreen (on the reverse side) onto the TPM header,
+aligned with the bolt hole, and make sure all pins sit tightly:
+
+![](images/turind8ud_tpm_adapter_close.jpg)
 
-![](images/turind8ud_tpm_flash.jpg)
+The TPM module goes back on the adapter's pass-through header, so the platform
+keeps its TPM while the flash stays reachable:
+
+![](images/turind8ud_tpm_adapter_installed.jpg)
+
+The second adapter mounts on the `SPI_1` header of the SPI extender HAT:
+
+![](images/turind8ud_tpm_adapter_hat.jpg)
+
+Route the cable from the motherboard down to the HAT:
+
+![](images/turind8ud_tpm_adapter_routing.jpg)
+
+For the TPM header pinout, refer to the
+[board's recovery section (setup with RTE)](../../variants/asrock_turind8ud/recovery.md#external-flashing).
 
 #### BMC flash
 
 `BMC_PH1` is a 2x5 1.27mm pitch header. Use the 1.27mm IDC connector to
-individual 2.54mm female DuPont connector cables to wire the `SPI_2` header to
+individual 2.54mm female connector cables to wire the `SPI_2` header to
 it according to the table:
 
 | `SPI_2` | BMC_PH1 pin |