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--- hidkey_gpio [2012/11/26 19:30] – [Results] steve_m
+++ hidkey_gpio [2013/02/27 00:10] (current) – [Results] steve_m
@@ Line 1: / Line 1: @@
 ====== AVR Programmer built from a USB Keyboard ======
-Recently, my old keyboard became louder and louder while typing, so I decided to buy a new one. But what to do with the old one? Ever since I saw the [[http://www.pjrc.com/hub_isp/|AVR programmer that uses a USB hub]], I thought of abusing a USB keyboard for that.
+Recently, my keyboard became louder and louder while typing, so I decided to buy a new one. But what to do with the old one? Ever since I saw the [[http://www.pjrc.com/hub_isp/|AVR programmer that uses a USB hub]], I thought of abusing a USB keyboard for that.
 ===== Theory =====
@@ Line 30: / Line 30: @@
 |Caps lock|MOSI|out|
 |Scroll lock|Reset|out|
-|row/column of right shift key|MISO|in|
+|row/column of right shift key|MISO (through optocoupler)|in|
 For the optocoupler I added a 470Ω current limiting resistor.
@@ Line 36: / Line 36: @@
 ===== Software =====
-First I wrote a small libusb-based test utility for experimenting with the keyboard. I'm directly communicating with the keyboard from userspace, unloading the kernel driver first.
+First I wrote a [[https://github.com/steve-m/hidkey_gpio|small libusb-based test utility]] for experimenting with the keyboard. I'm directly communicating with the keyboard from userspace, unloading the kernel driver first.
 ==== Speed ====
@@ Line 59: / Line 59: @@
 ==== Results ====
 <code>
-$ ./avrdude -c hidkey -C avrdude.conf -pattiny2313 -U flash:w:main.hex:i -V
+$ ./avrdude -c hidkey -C avrdude.conf -p attiny2313 -U flash:w:main.hex:i -V
 avrdude: AVR device initialized and ready to accept instructions
@@ Line 79: / Line 79: @@
 </code>
-Well, as you can see, programming takes quite a while, mainly because of the slow input speed I mentioned before, but is very reliable. Since I assume that many people have some old USB keyboard laying around collecting dust, it still could be used as a bootstrap flasher for solving the old chicken-and-egg problem when building a faster programmer ([[http://www.fischl.de/usbasp/|USBasp]], [[http://www.ladyada.net/make/usbtinyisp/|USBtinyISP]]) or as low-speed general purpose output for other applications. For example, many outputs could be driven using a simple serial-in, parallel-out shift register.
+Well, as you can see, programming takes quite a while, mainly because of the slow input speed I mentioned before, but is very reliable. Since I assume that many people have some old USB keyboard lying around collecting dust, it still could be used as a bootstrap flasher for solving the old chicken-and-egg problem when building a faster programmer ([[http://www.fischl.de/usbasp/|USBasp]], [[http://www.ladyada.net/make/usbtinyisp/|USBtinyISP]]) or as low-speed general purpose output for other applications. For example, many outputs could be driven using a simple serial-in, parallel-out shift register.
+===== Update #1 =====
+Since reading the MISO input is much slower than writing the outputs, as I mentioned above, I took a closer look at the avrdude code. As it turns out, the inputs are read every time, even if the data isn't used at all afterwards (like when writing a byte). I applied a crude hack, so that MISO is only being read if the data is used afterwards. I pushed that change to a new [[https://github.com/steve-m/avrdude/tree/speedup|speedup branch]] on github.
+With those changes, flashing my 86 byte demo application is now over ten times faster (11.75s vs. 123.79s)!
+<code>
+$ ./avrdude -c hidkey -C avrdude.conf -p attiny2313 -U flash:w:main.hex:i
+avrdude: AVR device initialized and ready to accept instructions
+Reading | ################################################## | 100% 4.33s
+avrdude: Device signature = 0x1e910a
+avrdude: NOTE: "flash" memory has been specified, an erase cycle will be performed
+         To disable this feature, specify the -D option.
+avrdude: erasing chip
+avrdude: reading input file "/home/steve/dev/hid_gpio/avr_demo/main.hex"
+avrdude: writing flash (86 bytes):
+Writing | ################################################## | 100% 11.75s
+avrdude: 86 bytes of flash written
+avrdude: verifying flash memory against /home/steve/dev/hid_gpio/avr_demo/main.hex:
+avrdude: load data flash data from input file /home/steve/dev/hid_gpio/avr_demo/main.hex:
+avrdude: input file /home/steve/dev/hid_gpio/avr_demo/main.hex contains 86 bytes
+avrdude: reading on-chip flash data:
+Reading | ################################################## | 100% 124.25s
+avrdude: verifying ...
+avrdude: 86 bytes of flash verified
+avrdude: safemode: Fuses OK
+avrdude done.  Thank you.
+</code>
+Programming the whole flash of the ATiny2313 now only takes 4 minutes 37 seconds:
+<code>
+$ ./avrdude -c hidkey -C avrdude.conf -p attiny2313 -U flash:w:/tmp/usbtiny.hex:i
+avrdude: AVR device initialized and ready to accept instructions
+Reading | ################################################## | 100% 4.33s
+avrdude: Device signature = 0x1e910a
+avrdude: NOTE: "flash" memory has been specified, an erase cycle will be performed
+         To disable this feature, specify the -D option.
+avrdude: erasing chip
+avrdude: reading input file "/tmp/usbtiny.hex"
+avrdude: writing flash (2046 bytes):
+Writing | ################################################## | 100% 276.90s
+avrdude: 2046 bytes of flash written
+avrdude: verifying flash memory against /tmp/usbtiny.hex:
+avrdude: load data flash data from input file /tmp/usbtiny.hex:
+avrdude: input file /tmp/usbtiny.hex contains 2046 bytes
+avrdude: reading on-chip flash data:
+Reading | ##########                                         | 20% 593.63s^C
+</code>
+I'd say that's quite an improvement, and very well acceptable for a chicken-and-egg bootstrap flasher :-)
+This project was featured on [[http://hackaday.com/2012/11/26/usb-keyboard-becomes-an-avr-programmer/|Hackaday]].
 == Reference Literature ==