Next part of board bringup: reset and power cycling.

- atusd/ERRATA: one more problem: the transistor footprint is wrong
- atusd/tools/lib/atusd.c (atusd_cycle, atusd_reset): added power cycling and
  hardware reset
- atusd/tools/lib/atusd.h: be nice and make a header file
- atusd/tools/try.c: be nice and use header files (caught a bug as well)

atusd/ERRATA

@@ -3,3 +3,6 @@
 
 - added wire connecting uSD-side ground plane to ground plane at outer edge,
   to improve CLK signal return. (Probably unnecessary, too.)
+
+- the footprint of the transistor (Q1) is reversed :-( It works after
+  converting the chip from SOT to PLCC.

atusd/tools/lib/atusd.c

@@ -1,6 +1,7 @@
 #include <stdint.h>
 #include <stdlib.h>
 #include <stdio.h>
+#include <unistd.h>
 #include <fcntl.h>
 #include <sys/mman.h>
 
@@ -102,7 +103,7 @@ struct atusd_dsc *atusd_open(void)
 
 void atusd_close(struct atusd_dsc *dsc)
 {
-	/* stop the MMC clock */
+	/* stop the MMC bus clock */
 	MSC_STRPCL = 1;
 
 	/* cut the power */
@@ -111,3 +112,52 @@ void atusd_close(struct atusd_dsc *dsc)
 	/* make all MMC pins inputs */
 	PDDIRC = MxSx | CLK | SCLK | SLP_TR | IRQ | nSEL;
 }
+
+
+void atusd_cycle(struct atusd_dsc *dsc)
+{
+	/* stop the MMC bus clock */
+	MSC_STRPCL = 1;
+
+	/* drive all outputs low (including the MMC bus clock) */
+	PDDATC = MxSx | CLK | SCLK | SLP_TR | nSEL;
+
+	/* make the MMC bus clock a regular output */
+	PDFUNC = CLK;
+
+	/* cut the power */
+	PDDATS = VDD_OFF;
+
+	/* Power drains within about 20 ms. Wait 100 ms to be sure. */
+	usleep(100*1000);
+
+	/* drive nSS high */
+	PDDATS = nSEL;
+
+	/* supply power */
+	PDDATS = VDD_OFF;
+
+	/* return the bus clock output to the MMC controller */
+	PDFUNS = CLK;
+
+	/* start MMC clock output */
+	MSC_STRPCL = 2;
+}
+
+
+void atusd_reset(struct atusd_dsc *dsc)
+{
+	/* activate reset */
+	PDDATS = SLP_TR;
+	PDDATC = nSEL;
+
+	/*
+	 * Data sheet says 625 ns, programmer's guide says 6 us. Whom do we
+	 * trust ?
+	 */
+	usleep(6);
+
+	/* release reset */
+	PDDATS = nSEL;
+	PDDATC = SLP_TR;
+}

atusd/tools/lib/atusd.h

@@ -0,0 +1,7 @@
+struct atusd_dsc;
+
+
+struct atusd_dsc *atusd_open(void);
+void atusd_close(struct atusd_dsc *dsc);
+void atusd_cycle(struct atusd_dsc *dsc);
+void atusd_reset(struct atusd_dsc *dsc);

atusd/tools/try.c

@@ -1,4 +1,7 @@
-struct atusd_dsc;
+#include <stdio.h>
+#include <unistd.h>
+
+#include "lib/atusd.h"
 
 
 int main(void)
@@ -7,7 +10,10 @@ int main(void)
 	char tmp;
 
 	dsc = atusd_open();
-	read(1, tmp, 1);
+	read(1, &tmp, 1);
+fprintf(stderr, "cycling\n");
+	atusd_cycle(dsc);
+	read(1, &tmp, 1);
 	atusd_close(dsc);
 
 	return 0;