diff --git a/20220405/Makefile b/20220405/Makefile
new file mode 100644
index 0000000000000000000000000000000000000000..7ae33df99f68fcf460324cfbb008f3f7a3863638
--- /dev/null
+++ b/20220405/Makefile
@@ -0,0 +1,8 @@
+%.elf: %.c
+ avr-gcc -Wall -Os -mmcu=atmega328p $< -o $@
+
+%.hex: %.elf
+ avr-objcopy -O ihex $< $@
+
+download:
+ ./download.sh
diff --git a/20220405/blink.c b/20220405/blink.c
new file mode 100644
index 0000000000000000000000000000000000000000..3970768da6772da0ccf8cbeaccbae49c200458f0
--- /dev/null
+++ b/20220405/blink.c
@@ -0,0 +1,18 @@
+#include <avr/io.h>
+
+#define F_CPU 8000000
+#include <util/delay.h>
+
+int main (void)
+{
+ DDRD = 0x01;
+ PORTD = 0x01;
+ while (1)
+ {
+ _delay_ms (500);
+ PORTD = 0x00;
+ _delay_ms (500);
+ PORTD = 0x01;
+ }
+ return 0;
+}
diff --git a/20220405/blink.hex b/20220405/blink.hex
new file mode 100644
index 0000000000000000000000000000000000000000..249b3aa15f72dc6a4f28f532fba154f486af5547
--- /dev/null
+++ b/20220405/blink.hex
@@ -0,0 +1,13 @@
+:100000000C9434000C943E000C943E000C943E0082
+:100010000C943E000C943E000C943E000C943E0068
+:100020000C943E000C943E000C943E000C943E0058
+:100030000C943E000C943E000C943E000C943E0048
+:100040000C943E000C943E000C943E000C943E0038
+:100050000C943E000C943E000C943E000C943E0028
+:100060000C943E000C943E0011241FBECFEFD8E04C
+:10007000DEBFCDBF0E9440000C9457000C940000DE
+:1000800081E08AB98BB92FEF34E39CE021503040F6
+:100090009040E1F700C000001BB82FEF34E39CE074
+:1000A000215030409040E1F700C00000EBCFF894C1
+:0200B000FFCF80
+:00000001FF
diff --git a/20220405/blink.s b/20220405/blink.s
new file mode 100644
index 0000000000000000000000000000000000000000..f3926c0f71679331dc5eff98a6605aa21b7df7aa
--- /dev/null
+++ b/20220405/blink.s
@@ -0,0 +1,40 @@
+ .file "blink.c"
+__SP_H__ = 0x3e
+__SP_L__ = 0x3d
+__SREG__ = 0x3f
+__tmp_reg__ = 0
+__zero_reg__ = 1
+ .section .text.startup,"ax",@progbits
+.global main
+ .type main, @function
+main:
+/* prologue: function */
+/* frame size = 0 */
+/* stack size = 0 */
+.L__stack_usage = 0
+ ldi r24,lo8(1)
+ out 0xa,r24
+.L3:
+ out 0xb,r24 ; #include <avr/io.h>
+ ldi r18,lo8(799999) ;
+ ldi r19,hi8(799999) ; #define F_CPU 8000000
+ ldi r25,hlo8(799999) ; #include <util/delay.h>
+1: subi r18,1 ;
+ sbci r19,0 ; int main (void)
+ sbci r25,0 ; {
+ brne 1b ; DDRD = 0x01;
+ rjmp . ; PORTD = 0x01;
+ nop ; while (1)
+ out 0xb,__zero_reg__ ; {
+ ldi r18,lo8(799999) ; _delay_ms (500);
+ ldi r19,hi8(799999) ; PORTD = 0x00;
+ ldi r25,hlo8(799999) ; _delay_ms (500);
+1: subi r18,1 ; PORTD = 0x01;
+ sbci r19,0 ; }
+ sbci r25,0 ; return 0;
+ brne 1b ; }
+ rjmp .
+ nop
+ rjmp .L3
+ .size main, .-main
+ .ident "GCC: (GNU) 5.4.0"
diff --git a/20220405/blink.txt b/20220405/blink.txt
new file mode 100644
index 0000000000000000000000000000000000000000..cfc4a99e54774d3d1f80ff3531065c43e36b8b5d
--- /dev/null
+++ b/20220405/blink.txt
@@ -0,0 +1,41 @@
+cassini/home/peter/bo/2022ss/rtech/20220405> cat blink.c
+#include <avr/io.h>
+
+#define F_CPU 8000000
+#include <util/delay.h>
+
+int main (void)
+{
+ DDRD = 0x01;
+ PORTD = 0x01;
+ while (1)
+ {
+ _delay_ms (500);
+ PORTD = 0x00;
+ _delay_ms (500);
+ PORTD = 0x01;
+ }
+ return 0;
+}
+cassini/home/peter/bo/2022ss/rtech/20220405> make blink.hex
+avr-gcc -Wall -Os -mmcu=atmega328p blink.c -o blink.elf
+avr-objcopy -O ihex blink.elf blink.hex
+rm blink.elf
+cassini/home/peter/bo/2022ss/rtech/20220405> cat blink.hex
+:100000000C9434000C943E000C943E000C943E0082
+:100010000C943E000C943E000C943E000C943E0068
+:100020000C943E000C943E000C943E000C943E0058
+:100030000C943E000C943E000C943E000C943E0048
+:100040000C943E000C943E000C943E000C943E0038
+:100050000C943E000C943E000C943E000C943E0028
+:100060000C943E000C943E0011241FBECFEFD8E04C
+:10007000DEBFCDBF0E9440000C9457000C940000DE
+:1000800081E08AB98BB92FEF34E39CE021503040F6
+:100090009040E1F700C000001BB82FEF34E39CE074
+:1000A000215030409040E1F700C00000EBCFF894C1
+:0200B000FFCF80
+:00000001FF
+cassini/home/peter/bo/2022ss/rtech/20220405> make download
+./download.sh
+avrdude -P /dev/ttyACM0 -c arduino -p m328p -U flash:w:blink.hex
+cassini/home/peter/bo/2022ss/rtech/20220405>
diff --git a/20220405/download.sh b/20220405/download.sh
new file mode 100755
index 0000000000000000000000000000000000000000..770c3b5dca74ac09778be055c9d6f5adb0df293b
--- /dev/null
+++ b/20220405/download.sh
@@ -0,0 +1,3 @@
+port=$(ls -rt /dev/ttyACM* | tail -1)
+echo avrdude -P $port -c arduino -p m328p -U flash:w:$(ls -rt *.hex | tail -1)
+avrdude -P $port -c arduino -p m328p -U flash:w:$(ls -rt *.hex | tail -1) 2>/dev/null
diff --git a/20220405/hello.c b/20220405/hello.c
new file mode 100644
index 0000000000000000000000000000000000000000..b767f77cd3a7328e5f45b60e674d32a647386509
--- /dev/null
+++ b/20220405/hello.c
@@ -0,0 +1,7 @@
+#include <stdio.h>
+
+int main (void)
+{
+ puts ("Hello, world!");
+ return 0;
+}
diff --git a/20220405/screenshot-20220405-124404.png b/20220405/screenshot-20220405-124404.png
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