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README.md: mention xmodem #10

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dancrossnyc merged 1 commit into from
Apr 15, 2025
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README.md: mention xmodem #10

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Expand Up @@ -96,6 +96,44 @@ equivalent to:
rz | @inflate | mount | load /platform/oxide/kernel/amd64/unix | call
```

## Transferring with XMODEM

Note that ZMODEM hasn't been completely reliable in testing. If
things appear to hang, try sending a BREAK. If that fails,
there is an XMODEM fallback in `bldb`, invoked via the `rx`
command at the REPL. XMODEM is a receiver-initiated protocol,
and to avoid a race condition between the receiver issuing the
transfer handshake and the sender invoking the XMODEM send
program (e.g., `sx`), `bldb` will wait for a single character to
arrive on the UART before starting the protocol. This character
must be the ASCII lower-case letter 'g'; any other letter will
abort the transfer and return to the REPL.

One may use a script to automate this, such as
[`sxmodem`](https://github.com/oxidecomputer/bldb/blob/main/sxmodem)
in this repository:

```
#!/bin/ksh93
printf g
exec sx -vv -Xk "$@"
```

With this, one can transfer, inflate, mount, load, and call into Unix as:

```
call . load /platform/oxide/kernel/amd64/unix . mount . @inflate . rx
```

Or, if one prefers,

```
rx | @inflate | mount | load /platform/oxide/kernel/amd64/unix | call
```

See also the
[`rconsx` script](https://github.com/oxidecomputer/bldb/blob/main/rconsx).

## Commands

The reader supports a handful of "reader commands":
Expand Down