Ascii unconditionally appends an extra newline, which prevents use for generating arbitrary byte sequences (like ascii -tx ff 0 >/dev/spi0). Man page says, under -t option newline should not be inserted, and it is not appended by the related unicode tool.

Reference: /n/sources/patch/ascii-extra-newline
Date: Thu Aug 31 01:11:06 CES 2017
Signed-off-by: antox@ml.lv

--- /sys/src/cmd/ascii.c	Thu Aug 31 00:59:26 2017
+++ /sys/src/cmd/ascii.c	Thu Aug 31 00:59:22 2017
@@ -106,7 +106,6 @@
 			else
 				putnum(*argv++);
 	}
-	Bputc(&bin, '\n');
 	exits(0);
 }
 void