comparison: content/hp34970a_protocol.rst
content/hp34970a_protocol.rst
- changeset 111
- 25cae2c53694
- parent 69
- 56bcb94f6ff5
- child 115
- 6b6e13653348
equal
deleted
inserted
replaced
| 110:64b852fb7470 | 111:25cae2c53694 |
|---|---|
| 5 :Author: David Douard | 5 :Author: David Douard |
| 6 :Category: Electronics | 6 :Category: Electronics |
| 7 :Tags: HP, 34970A, DMM, repair, test equipment | 7 :Tags: HP, 34970A, DMM, repair, test equipment |
| 8 :series: HP 34970A repair | 8 :series: HP 34970A repair |
| 9 :JavaScripts: default.js, WaveDrom.js | 9 :JavaScripts: default.js, WaveDrom.js |
| 10 | 10 |
| 11 In order to build a replacement display for the HP34970A data | 11 In order to build a replacement display for the HP34970A data |
| 12 acquisition unit, I needed to understand the communication protocol | 12 acquisition unit, I needed to understand the communication protocol |
| 13 between the CPU board and the front panel assembly. | 13 between the CPU board and the front panel assembly. |
| 14 | 14 |
| 15 General description | 15 General description |
| 26 - A4 is the (optional) internal 6.5 digits DMM. | 26 - A4 is the (optional) internal 6.5 digits DMM. |
| 27 | 27 |
| 28 .. image:: {filename}/images/hp34970a/block_diagram.svg | 28 .. image:: {filename}/images/hp34970a/block_diagram.svg |
| 29 :alt: System Block Diagram of the HP34970A. | 29 :alt: System Block Diagram of the HP34970A. |
| 30 | 30 |
| 31 | 31 |
| 32 The commnucation between the different system blocks is done with | 32 The commnucation between the different system blocks is done with |
| 33 asynchronous serial links. They use the rather uncommon bit rate of | 33 asynchronous serial links. They use the rather uncommon bit rate of |
| 34 187500 baud, with a classic 8N1 schema. | 34 187500 baud, with a classic 8N1 schema. |
| 35 | 35 |
| 36 | 36 |
| 54 not acknowledge a received byte, but sending a SoT instead of the | 54 not acknowledge a received byte, but sending a SoT instead of the |
| 55 expected ACK value, | 55 expected ACK value, |
| 56 | 56 |
| 57 - acknowledge values are: | 57 - acknowledge values are: |
| 58 | 58 |
| 59 - 0x99 as a response to the SoT, | 59 - one-complement of the received SoT byte, so |
| 60 | |
| 61 - 0x99 for the 0x66 SoT byte and | |
| 62 - 0xCC for the 0x33 SoT byte. | |
| 60 | 63 |
| 61 - 0x00 otherise | 64 - 0x00 otherise |
| 62 | 65 |
| 66 - a special packet is sent by the Display Panel at startup, which SoT value is | |
| 67 ``0x33``, which does not seem to follow the general pattern in which the first | |
| 68 value after the SoT byte is the number of arguments. | |
| 69 | |
| 70 Initialization sequence | |
| 71 ----------------------- | |
| 72 | |
| 73 The initialization transmission is: | |
| 74 | |
| 75 .. wavedrom:: | |
| 76 | |
| 77 { signal: [ | |
| 78 {name: "CPU", wave: "zz5x5x5xx", data: ["0xCC", "0x00", "0x00"]}, | |
| 79 {name: "DP", wave: "z3x4x4x3x", data: ["0x33", "0x02", "0x00", "0x55"]}, | |
| 80 ]} | |
| 81 | |
| 82 If a key is pressed during while powering the unit on, then the initialization | |
| 83 of the Display Panel is frozen (with all elements of the display lit) until the | |
| 84 key is released. In this case, the initialization packet adds the key code of | |
| 85 that key, typically used with the Shift key pressed in to force a full test of | |
| 86 the device (in this datagram, ``0x0C`` is the keycode of the Shift key): | |
| 87 | |
| 88 .. wavedrom:: | |
| 89 | |
| 90 { signal: [ | |
| 91 {name: "CPU", wave: "zz5x5x5x5xx", data: ["0xCC", "0x00", "0x00", "0x00"]}, | |
| 92 {name: "DP", wave: "z3x4x4x4x3x", data: ["0x33", "0x02", "0xFF", "0x0C", "0x55"]}, | |
| 93 ]} | |
| 94 | |
| 95 | |
| 96 Shutdown sequence | |
| 97 ----------------- | |
| 98 | |
| 99 .. wavedrom:: | |
| 100 | |
| 101 { signal: [ | |
| 102 {name: "Rx", wave: "z3x4x44|=4", data: ["0x66", "0x86", "0x55", "0x55","0x55"] }, | |
| 103 {name: "Tx", wave: "zx5x5xx", data: ["0x99", "0x00"] }, | |
| 104 ]} | |
| 105 | |
| 106 | |
| 107 CPU -> DP trasmission | |
| 108 --------------------- | |
| 63 | 109 |
| 64 The CPU->DP transmission protocol looks like: | 110 The CPU->DP transmission protocol looks like: |
| 65 | 111 |
| 66 .. wavedrom:: | 112 .. wavedrom:: |
| 67 | 113 |
| 74 ie. without sending the EoT byte, eg.: | 120 ie. without sending the EoT byte, eg.: |
| 75 | 121 |
| 76 .. wavedrom:: | 122 .. wavedrom:: |
| 77 | 123 |
| 78 { signal: [ | 124 { signal: [ |
| 79 {name: "Rx", wave: "z3x4x4x|=x3x4x|3x", | 125 {name: "Rx", wave: "z3x4x4x|=x3x4x|3x", |
| 80 data: ["0x66", "0x0C", "0x03", "D3", "0x66", "0x0A", "0x55"] }, | 126 data: ["0x66", "0x0C", "0x03", "D3", "0x66", "0x0A", "0x55"] }, |
| 81 {name: "Tx", wave: "zx5x5x5x|5x5x5x|x", | 127 {name: "Tx", wave: "zx5x5x5x|5x5x5x|x", |
| 82 data: ["0x99", "0x00", "0x00", "0x00", "0x99", "0x00"] }, | 128 data: ["0x99", "0x00", "0x00", "0x00", "0x99", "0x00"] }, |
| 83 ]} | 129 ]} |
| 84 | 130 |
| 85 | 131 |
| 132 DP -> CPU transmission | |
| 133 ---------------------- | |
| 134 | |
| 86 When the user press a key on the front panel, a slightly simpler "packet transmission" occurs: | 135 When the user press a key on the front panel, a slightly simpler "packet transmission" occurs: |
| 87 | 136 |
| 88 .. wavedrom:: | 137 .. wavedrom:: |
| 89 | 138 |
| 90 { signal: [ | 139 { signal: [ |
| 91 {name: "Rx", wave: "zz5x5xx", data: ["0x99", "0x00"]}, | 140 {name: "Rx", wave: "zz5x5xx", data: ["0x99", "0x00"]}, |
| 92 {name: "Tx", wave: "z3x4x3x", data: ["0x66", "KP", "0x55"]}, | 141 {name: "Tx", wave: "z3x4x3x", data: ["0x66", "KP", "0x55"]}, |
| 93 ]} | 142 ]} |
| 94 | 143 |
| 144 | |
| 145 Commands | |
| 146 ======== | |
| 147 | |
| 148 The known command bytes sent by the CPU for now are: | |
| 149 | |
| 150 :0x00: show text on the main display. N arguments; the characters to display. | |
| 151 | |
| 152 :0x0C: show text in the 'channels' area. 3 arguments; the digits to display. | |
| 153 | |
| 154 :0x0A: indicators (or flags) to display. 4 arguments; the flag bytes. | |
| 155 | |
| 156 :0x08: to set an indicator in low bright mode. 1 argument; the number of the | |
| 157 indicator dimm. | |
| 158 | |
| 159 :0x09: to set an indicator in hight bright mode. 1 argument; the number of the | |
| 160 indicator to highlight. | |
| 161 | |
| 162 :0x01: clear the 'shift' button. Typically sent as ``0x01 0x01 0x0E``. 1 | |
| 163 argument; 0x0E to clear the 'shift' flag. Other values unknown. | |
| 164 | |
| 165 :0x02: might be a reset or clear for the front panel (typically sent as | |
| 166 ``0x02 0x01 0x0C`` packet). 1 argument; unknown. | |
| 167 | |
| 168 :0x86: shutdown. 0 argument. | |
| 169 | |
| 170 :0x0D: set char at pos dimm (eg 0D 01 02 55 = cursor on the 3rd char) | |
| 95 | 171 |
| 96 Sending data to the main display | 172 Sending data to the main display |
| 97 ================================ | 173 ================================ |
| 98 | 174 |
| 99 The main display consist in 13 17-segments digits, in which the | 175 The main display consist in 13 17-segments digits, in which the |
| 102 ",", ":" and ";"). Punctuation signs are also very close to the | 178 ",", ":" and ";"). Punctuation signs are also very close to the |
| 103 preceding chracters. | 179 preceding chracters. |
| 104 | 180 |
| 105 .. image:: {filename}/images/hp34970a/digit.jpg | 181 .. image:: {filename}/images/hp34970a/digit.jpg |
| 106 :alt: 17-segments digit of the main display. | 182 :alt: 17-segments digit of the main display. |
| 107 | 183 |
| 108 The command used to send text to the main display is ``0x00``. The | 184 The command used to send text to the main display is ``0x00``. The |
| 109 character ``0x09`` (tabulation) has a special meaning: it marks the | 185 character ``0x09`` (tabulation) has a special meaning: it marks the |
| 110 beginning and the end of a part of the text to be displayed darker | 186 beginning and the end of a part of the text to be displayed darker |
| 111 than the usual. This is used to emphasis a portion of the displayed | 187 than the usual. This is used to emphasis a portion of the displayed |
| 112 text. Also, as the punctuation signs do not consume a digit, the | 188 text. Also, as the punctuation signs do not consume a digit, the |
| 137 { signal: [ | 213 { signal: [ |
| 138 {name: "Rx", wave: "z344====3x", | 214 {name: "Rx", wave: "z344====3x", |
| 139 data: ["0x66", "0x0A", "0x04", "F1", "F2", "F3", "F4", "0x55"]} | 215 data: ["0x66", "0x0A", "0x04", "F1", "F2", "F3", "F4", "0x55"]} |
| 140 ]} | 216 ]} |
| 141 | 217 |
| 142 Then the flags I've identified so far are: | 218 The 29 flags I've identified are (should be complete): |
| 143 | 219 |
| 144 .. wavedrom:: | 220 .. wavedrom:: |
| 145 | 221 |
| 146 { signal: [ | 222 { signal: [ |
| 147 {name: "bit", wave: "z========z", | 223 {name: "bit", wave: "z========z", |
| 148 data: ["7", "6", "5", "4", "3", "2", "1", "0"]}, | 224 data: ["7", "6", "5", "4", "3", "2", "1", "0"]}, |
| 149 | 225 |
| 150 {name: "F1", wave: "z=3333333z", | 226 {name: "F1", wave: "z=3333333z", |
| 151 data: ["", "HI", "Alarm", "LO", "Channels", "Ch. frame", "Mx+B", "<Bell>"]}, | 227 data: ["Al. frame", "HI", "Alarm", "LO", "Channel", "Ch. frame", "Mx+B", "<Bell>"]}, |
| 152 {name: "F2", wave: "z===33333z", | 228 {name: "F2", wave: "z===33333z", |
| 153 data: ["", "", "", "4W", "1", "3", "4", "2"]}, | 229 data: ["AVG", "", "OC", "4W", "1", "3", "4", "2"]}, |
| 154 {name: "F3", wave: "z========z", | 230 {name: "F3", wave: "z========z", |
| 155 data: ["", "", "", "", "", "", "", ""]}, | 231 data: ["ERROR", "EXT", "ONCE", "", "MEM", "LAST", "MIN", "MAX"]}, |
| 156 {name: "F4", wave: "z=3=333==z", | 232 {name: "F4", wave: "z=3=333==z", |
| 157 data: ["", "CONFIG", "", "MON", "VIEW", "*", "", ""]}, | 233 data: ["", "CONFIG", "SCAN", "MON", "VIEW", "*", "ADRS", "REMOTE"]}, |
| 158 ], | 234 ], |
| 159 config: { hscale: 2 }, | 235 config: { hscale: 2 }, |
| 160 } | 236 } |
| 161 | 237 |
| 162 | |
| 163 | |
| 164 | |
| 165 | 238 |
| 166 Keypad | 239 Keypad |
| 167 ====== | 240 ====== |
| 168 | 241 |
| 169 Note that the front panel sends a "key press event" and a "key | 242 the keycode byte consists in: |
| 170 released event", depending on the value of the bit 7: | |
| 171 | |
| 172 :0: key pressed | |
| 173 :1: key released | |
| 174 | |
| 175 The bit 8 of the key event byte is set high for the knob. | |
| 176 | 243 |
| 177 .. wavedrom:: | 244 .. wavedrom:: |
| 178 | 245 |
| 179 {signal: [ | 246 {signal: [ |
| 180 | 247 |
| 181 {name: "bit", wave: "z========z", | 248 {name: "bit", wave: "z========z", |
| 182 data: ["7", "6", "5", "4", "3", "2", "1", "0"]}, | 249 data: ["7", "6", "5", "4", "3", "2", "1", "0"]}, |
| 183 {name: "KP", wave: "z34=.....z", | 250 {name: "KP", wave: "z344=....z", |
| 184 data: ["Knob", "Key", "Key Code"]}, | 251 data: ["Knob", "Rel.", "Shift", "Key Code"]}, |
| 185 ], | 252 ], |
| 186 config: { hscale: 1 }, | 253 config: { hscale: 1 }, |
| 187 } | 254 } |
| 255 | |
| 256 :Bit 5: is set when the key has been pressed while 'shift' indicator was stil | |
| 257 active. | |
| 258 | |
| 259 :Bit 6: is set when the key is released, and clear for the key pressed event. | |
| 260 | |
| 261 :Bit 7: of the key event byte is set high for the knob key events. | |
| 188 | 262 |
| 189 | 263 |
| 190 The key codes are: | 264 The key codes are: |
| 191 | 265 |
| 192 :0x00: View | 266 :0x00: View |
| 207 :0x0F: Right | 281 :0x0F: Right |
| 208 | 282 |
| 209 :0x10: Advanced | 283 :0x10: Advanced |
| 210 :0x11: Step | 284 :0x11: Step |
| 211 | 285 |
| 212 For the knob (including the "Knob" bit): | 286 :0x80: Knob right |
| 213 :0x80: Knob left | 287 :0x81: Knob left |
| 214 :0x81: Knob right |
