Send a partial update in the date example

From what I've read it's not good to always do full updates, so for examples and
testing I figure that doing a partial update of the whole screen is also good.

configure.ac

@@ -23,7 +23,7 @@ if test "x$GUILD" = "x"; then
 fi
 
 dnl Hall auto-generated guile-module dependencies
-
+GUILE_MODULE_REQUIRED([termios])
 
 dnl Installation directories for .scm and .go files.
 guilemoduledir="${datarootdir}/guile/site/$GUILE_EFFECTIVE_VERSION"

examples/date.scm

@@ -1,4 +1,4 @@
-(use-modules ((inkplate lowlevel) #:prefix inkplate:)
+(use-modules ((inkplate) #:prefix inkplate:)
              (srfi srfi-19))
 
 (let ((my-dev (inkplate:open "/dev/ttyUSB0")))
@@ -16,7 +16,7 @@
   (inkplate:draw-rectangle my-dev 269 89 252 157 3)
   (inkplate:draw-rectangle my-dev 268 88 254 159 3)
 
-  (inkplate:update my-dev)
+  (inkplate:partial-update my-dev 15 800 600)
   (inkplate:send my-dev)
 
   (inkplate:close my-dev))

guix.scm

@@ -23,7 +23,8 @@
       ("pkg-config" ,pkg-config)
       ("texinfo" ,texinfo)))
   (inputs `(("guile" ,guile-3.0)))
-  (propagated-inputs `())
+  (propagated-inputs
+   `(("guile-termios" ,guile-termios)))
   (synopsis "")
   (description "")
   (home-page "")

hall.scm

@@ -8,7 +8,7 @@
   (description "")
   (home-page "")
   (license gpl3+)
-  (dependencies `())
+  (dependencies `(("guile-termios" (termios) ,guile-termios)))
   (skip ())
   (files (libraries ((scheme-file "inkplate")))
          (tests ((directory "tests" ((scheme-file "inkplate")))))

inkplate.scm

@@ -1,6 +1,13 @@
 (define-module (inkplate)
   #:use-module ((ice-9 format) #:select (format))
   #:use-module ((srfi srfi-9) #:select (define-record-type))
+  #:use-module ((termios system) #:select (termios-B115200))
+  #:use-module ((termios with-exceptions)
+                #:select (make-termios-struct
+                          tc-get-attr!
+                          tc-set-attr
+                          cf-make-raw!
+                          cf-set-speed!))
 
   #:export (<inkplate>
             make-inkplate
@@ -62,8 +69,13 @@
 
 (define (open device-path)
   "Open a connection to an Inkplate on the named DEVICE-PATH."
-  (let ((port (open-file device-path "r+")))
-   (make-inkplate port port)))
+  (let ((port (open-file device-path "r+"))
+        (termios (make-termios-struct)))
+    (tc-get-attr! port termios)
+    (cf-make-raw! termios)
+    (cf-set-speed! termios termios-B115200)
+    (tc-set-attr port termios)
+    (make-inkplate port port)))
 
 (define (close device)
   "Close a connection to an Inkplate in DEVICE."