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   3                                                                 <Title>
   4 MBino (Rev. C)
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   7                                                                 <Body>
   8                                                                 <H1>
   9 MBino (Rev. C)
  10                                                                 </H1>
  11                                                                 <P>
  12                                                                 </P>
  13                                                                 <H2>
  14 Table of Contents
  15                                                                 </H2>
  16                                                                 <P>
  17                                                                 <UL><LI>
  18         <A HRef="#Schematic">
  19     1.0 Schematic</A>
  20                                                                 </LI><LI>
  21         <A HRef="#Design_Files">
  22     2.0 Design Files</A>
  23                                                                 </LI><LI>
  24         <A HRef="#Errata_and_Notes">
  25     3.0 Errata and Notes</A>
  26                                                                 </LI><LI>
  27         <A HRef="#Bootloader">
  28     4.0 Bootloader</A>
  29                                                                 </LI><LI>
  30         <A HRef="#IDE">
  31     5.0 IDE</A>
  32                                                                 </LI></UL>
  33                                                                 </P>
  34                                                                 <H2>
  35     <A Name="Schematic">
  36 1.0 Schematic</A>
  37                                                                 </H2>
  38                                                                 <P>
  39 The schematic is available as either a
  40     <A HRef="busduino.pdf">
  41 .pdf</A> file or as a
  42     <A HRef="busduino.svg">
  43 .svg</A> (Scalable Vector Graphics) file.
  44 The .pdf file should print reasonably well on a black
  45 and white printer.  The .svg file is embedded below:
  46                                                                 </P>
  47
  48     <Img Src="busduino.svg">
  49                                                                 <P>
  50 There are two 2.1mm power jacks , N1 and N3.
  51 N1 feeds power through protection diode D1 and
  52 protection resettable polyfuse F2 to the LPWR1
  53 and LWPR2 pins of MakeBus connector N2.  D1 protects
  54 everthing if the power accidentally comes in with
  55 reverse polarity on N1.  (Connector N2 is labeled as
  56 "Robus" which is the previous bus name to "MakerBus".)
  57 The ground line of N1 is also connected to LGND1
  58 and LGND2 of N2.  The same thing happens with N3,
  59 F1, and D2 with BPWR1, BPWR2, BGND1, and BGND2 on N2.
  60                                                                 </P><P>
  61 The LPWR1 and LPWR1 lines from N2 are further connected
  62 to the 5V linear regulator U1 and the 3.3V linear
  63 regulator U2 to provide 5 volts and 3.3 volts respectively.
  64                                                                 </P><P>
  65 CANH and CANL of N2 or connected to the 5V CAN bus
  66 transceiver chip U3.  The 1 &times; 3 jumper J1 can
  67 be jumpered to connect a 124 ohm termination resistor R6.
  68 The 24K resistor R9 enables slope control for U3.
  69 The TXD and RXD pins are connected to the microcontroller
  70 U4 pins PD3 (TXD1) and PD2 (RXD1).  Capacitors C5-C10
  71 are .1&micro;F bypass capacitors for U4 and U3.
  72 16MHz crystal X1 and crystal 22pF capactiors C4 and C5
  73 provide the 16MHz frequency reference for U4.
  74                                                                 </P><P>
  75 Connector N4 is a 2&times;8 pin combined JTAG and
  76 serial download connector that connects to the
  77 various JTAG pins on the microcontroller (U4).
  78 The serial debug lines from N4 are also connected
  79 to the 1&times;6 serial cable pin N5 before
  80 connecting to PD1 (TXD0) and PD0 (RXD0) on U4
  81 through 1K ohm resistors R2 and R3.  R2 and R3
  82 pins D0 (N9) and D1 (N9) to have priority over
  83 over both N4 and N5 is voltage sources are connected
  84 to both at the same time.  It is a really bad idea
  85 to attempt to use both N4 and N5 for serial downloading
  86 at the same time.  10K ohm resistor R1 and 1&micro;F
  87 capacitor C12 provide a simple reset circuit to trigger
  88 RESET on U4.  The reset button SW1 can also be used
  89 to manually reset U4.
  90                                                                 </P><P>
  91 470 Ohm resistor R8 and LED D4 are connected to D13
  92 (N8) to provide an on-board LED.  470 ohm resistor R7
  93 and bicolor LED D3 are only meant to be used for
  94 debugging; they are not installed in the final product.
  95 Connectors N6 (Power/Reset pins), N7 (ISP header),
  96 N8 (D0-D13, GND, AREF), N9 (D0-D7) and N10 (A0-A5)
  97 are used used to connect to Arduino compatible shields.
  98                                                                 </P><P>
  99 4.7K ohm resistors R4 and R5 are available to be used
 100 as pull up resistors for the I<Sup>2</Sup>C bus pins
 101 connected to D13 (SCK) and D12 (MISO) pins on U4.
 102                                                                 </P>
 103                                                                 <H2>
 104     <A Name="Design_Files">
 105 2.0 Design Files</A>
 106                                                                 </H2>
 107                                                                 <P>
 108 This board was designed using KiCAD.  A complete KiCAD
 109 archive of board is found in
 110     <A HRef="busduino.zip">
 111 busduino.zip</A>.  ("BusDuino" was the original name
 112 of the board before it was renamed to "MBino".)
 113 When this file is unzipped, the KiCad project file
 114 can be found down in
 115 <Code>robus/busdino/rev_b/busdino.pro</Code>.  Various
 116 shared <Code>.mod</Code> and <Code>.lib</Code> files
 117 are kept in the <Code>robus</Code> directory.  All
 118 Gerber and drill files are generated using KiCad.
 119                                                                 </P>
 120                                                                 <H2>
 121     <A Name="Errata_and_Notes">
 122 3.0 Errata and Notes</A>
 123                                                                 </H2>
 124                                                                 <P>
 125 The following errors and issues are noted:
 126                                                                 <UL><LI>
 127     U1 Vin/Vout pins are swapped
 128                                                                 </LI><LI>
 129     A reset circuit from MakerBus is needed.
 130                                                                 </LI></UL>
 131                                                                 </P><P>
 132 The design notes for the reset circuit are:
 133                                                                 <UL><LI>
 134 Use a SNLVC2G06 (dual open collector inverter):
 135                                                                 </LI><LI>
 136 At VCC = 5V:
 137                                                                 <UL><LI>
 138    V<Sub>IH</Sub> = .7 * V<Sub>CC</Sub> = 3.5V
 139                                                                 </LI><LI>
 140    V<Sub>IL</Sub> = .3 * V<Sub>CC</Sub> = 1.5V
 141                                                                 </LI><LI>
 142    V<Sub>OL</Sub> = .55V
 143                                                                 </LI><LI>
 144    I<Sub>OL</Sub> = 32mA
 145                                                                 </LI></UL>
 146                                                                 </LI><LI>
 147 Assuming that the capacitor is clamped to VOL most
 148 of the time, the R*C that corresponds to charging
 149 from VOL to VIH in T seconds is the
 150 the basic capacitor charging equation:
 151                                                                 </LI><UL><LI>
 152   V(t) = V<Sub>OL</Sub> + (V<Sub>CC</Sub> -
 153      V<Sub>OL</Sub>) * (1 - e<Sup>-t/R*C</Sup>)
 154                                                                 </LI></UL><LI>
 155 Replacing V(t) with V<Sub>IH</Sub> and T:
 156                                                                 <UL><LI>
 157   V<Sub>IH</Sub> = V<Sub>OL</Sub> + (V<Sub>CC</Sub> -
 158     V<Sub>OL</Sub>) * (1 - e<Sup>-T/R*C</Sup>)
 159                                                                 </LI></UL>
 160                                                                 </LI><LI>
 161 Solving for RC:
 162                                                                 <UL><LI>
 163   (V<Sub>IH</Sub> - V<Sub>OL</Sub>)/(V<Sub>CC</Sub> - V<Sub>L</Sub>) =
 164   1 - e<Sup>-T/R*C</Sup>
 165                                                                 </LI><LI>
 166   e<Sup>-T/R*C</Sup> = 1 - (V<Sub>IH</Sub> -
 167     V<Sub>OL</Sub>)/(V<Sub>CC</Sub> - V<Sub>OL</Sub>)
 168                                                                 </LI><LI>
 169   -T/R*C = ln(1 - (V<Sub>IH</Sub> -
 170     V<Sub>OL</Sub>)/(V<Sub>CC</Sub> - V<Sub>OL</Sub>))
 171                                                                 </LI><LI>
 172   R*C = -T/ln(1 - (V<Sub>IH</Sub> -
 173     V<Sub>OL</Sub>)/(V<Sub>CC</Sub> - V<Sub>OL</Sub>))
 174                                                                 </LI></UL>
 175                                                                 </LI><LI>
 176 Substituting in for T=1mS, V<Sub>IH</Sub>,
 177 V<Sub>OL</Sub>, and V<Sub>CC</Sub>:
 178                                                                 <UL><LI>
 179   R*C =  -.001/ln(1 - (3.5 - .55)/(5 - .55))
 180                                                                 </LI><LI>
 181   R*C = -.001/-1.08744
 182                                                                 </LI><LI>
 183   R*C = .009196
 184                                                                 </LI></UL>
 185                                                                 </LI><LI>
 186 Setting C = .1&micro;F
 187                                                                 <UL><LI>
 188   R = .009196 / .0000001 = 9196
 189                                                                 </LI></UL>
 190 Using an R near 10K should do the trick.
 191                                                                 </LI><LI>
 192 The maximum discharge current is I<Sub>OL</Sub>.  Use Ohm's law
 193 to determine determine discharge resistor:
 194                                                                 <UL><LI>
 195    V = I * R
 196                                                                 </LI><LI>
 197    R = V / I
 198      = 5 / .032
 199      = 156.25
 200                                                                 </LI></UL>
 201 Setting R<Sub>discharge</Sub> = 180 should be good enough.
 202                                                                 </LI><LI>
 203 The charge/discharge ratio is:
 204                                                                 <UL><LI>
 205   R<Sub>charge</Sub>/R<Sub>discharge</Sub> = 10K/180 = 55.5
 206                                                                 </LI></UL>
 207                                                                 </LI></UL>
 208                                                                 <P>
 209                                                                 <H2>
 210     <A Name="Bootloader">
 211 4.0 Bootloader</A>
 212                                                                 </H2>
 213                                                                 <P>
 214 {Bootloader discussion goes here!}
 215                                                                 </P>
 216                                                                 <H2>
 217     <A Name="IDE">
 218 5.0 IDE</A>                                                     </H2>
 219                                                                 <P>
 220 The following URL specifies how to add a new board:
 221                                                                 <BlockQuote>
 222
 223         <A HRef="http://www.avr-developers.com/corefiles/index.html">
 224     http://www.avr-developers.com/corefiles/index.html</A>
 225                                                                 </BlockQuote>
 226                                                                 </P><P>
 227 The short answer is:
 228                                                                 <Pre>
 229     cd .../hardware
 230     (cd arduino; tar cvf /tmp/arduino.tar .)
 231     (mkdir {your_board_dir}; tar xvf /tmp/arduino.tar)
 232     # now edit {your_board_dir}/boards.txt to configure your board
 233     # now edit {your_board_dir}/programmers.txt
 234                                                                 </Pre>
 235 The problem with this strategy is that you get a snap-shot of
 236 all the files and everything becomes out of date when the next
 237 release of the Arduino IDE comes out.  A better way is probably
 238 to have a shell script that make a copy of arduino files followed
 239 by a file that unzips the stuff that needs to be changed.  That
 240 may be just a few files.
 241                                                                 </P><P>
 242 Here are the files that have been edited so far:
 243                                                                 <DL><DT>
 244   .../MBino/variants/standard/pins_arduino.h:                   </DT><DD>
 245                                                                 <Pre>
 246     // Add 4 pins to the vector for I2C SDA, SCL, and external pull-ups
 247     SDA = 20
 248     SCL = 21
 249
 250     port_to_mode_PGM = {
 251         // Add &DDRA,   // ATmega324 has a Port A
 252
 253     port_to_output_PGM = {
 254         // Add &PORTA,  // ATmega324 has a Port A
 255
 256     port_to_input_PGM = {
 257         // Add &PINA,   // ATmega324 has a Port A
 258
 259     digital_pin_to_port_PGM = {
 260         // Remap digital pin ports
 261
 262     digital_pin_to_bit_mask_PGM = {
 263         // Remap bit masks
 264                                                                 </Pre>
 265 Obviously thes is pretty minor changes.
 266                                                                 </DD></DL>
 267                                                                 </P><P>
 268 {Create a .zip file that creates the various MBino
 269 sub-directories for the Arduino IDE.}
 270                                                                 </P>
 271                                                                 <HR>
 272                                                                 <Address>
 273     <A HRef="http://gramlich.net/copyright.html">
 274 Copyright</A> 2013 by
 275     <A HRef="http://gramlich.net/index.html">
 276 Wayne C. Gramlich</A>.
 277 All rights reserved.
 278                                                                 </Address>
 279                                                                 </Body>
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