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Hi James,<br>
<br>
That's really useful thanks. I have some background in USB
development so can see where you are coming from with this.<br>
<br>
Am I right in thinking that the device is a HID class device, or is
it more custom than this? (thinking about Windows driver support
here)<br>
<br>
I had assumed that it would be enumerating as a standard serial
class device and you would have a protocol running over the <br>
virtualised serial link, this being easier in terms of driver
support on host OS platforms.<br>
<br>
Was there a reason for not going down the USB serial route? I am
wondering how difficult that would be for me to put in place?<br>
<br>
Thanks!<br>
<br>
Alex<br>
<br>
<div class="moz-cite-prefix">On 06/02/2014 12:46, James Pallister
wrote:<br>
</div>
<blockquote cite="mid:52F3843C.6000305@bristol.ac.uk" type="cite">
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
<div class="moz-cite-prefix">Hi Alex,<br>
<br>
I haven't gotten round to writing up the protocol yet, but it is
reasonably simple. Here is a fairly long and detailed email,
which will probably be copied to the wiki at some point.<br>
<br>
<br>
The device appears as a custom USB device, and all of the
commands are sent as control transfers. There is almost a
one-to-one mapping between the methods in the <tt>pyenergy.EnergyMonitor</tt>
class and the control transfers performed to the device. The
only slight complication is there are 3 ADCs and 4 measurement
points, the mapping of which ADC measures which measurement
point is done in the <tt>enableMeasurementPoint</tt> method
(with request number 7).<br>
<br>
For the exact details, see: <a moz-do-not-send="true"
href="https://github.com/jpallister/stm32f4-energy-monitor/blob/pyusb/src/python/pyenergy.py">https://github.com/jpallister/stm32f4-energy-monitor/blob/pyusb/src/python/pyenergy.py</a><br>
<br>
The actual control transfers themselves use the <tt>bRequest</tt>
parameter of the control transfer to differentiate between types
of action. The <tt>wValue</tt> and <tt>wIndex</tt> parameters
both specify data for that particular request. There are many
possible requests:<br>
<br>
<table cellpadding="2" cellspacing="2" width="100%" border="1">
<tbody>
<tr>
<td valign="top">Request
<meta http-equiv="content-type" content="text/html;
charset=ISO-8859-1">
<br>
</td>
<td valign="top">bRequest</td>
<td valign="top">wValue</td>
<td valign="top">wIndex</td>
<td valign="top">Description</td>
</tr>
<tr>
<td valign="top">Toggle LEDS<br>
</td>
<td valign="top">0<br>
</td>
<td valign="top">N/A<br>
</td>
<td valign="top">N/A<br>
</td>
<td valign="top">Toggle one of the LEDs on the board<br>
</td>
</tr>
<tr>
<td valign="top">Start Measurement<br>
</td>
<td valign="top">1<br>
</td>
<td valign="top">Measurement point<br>
</td>
<td valign="top">N/A<br>
</td>
<td valign="top">Start measuring the measurement point
specified by wValue<br>
</td>
</tr>
<tr>
<td valign="top">Stop Measurement<br>
</td>
<td valign="top">2<br>
</td>
<td valign="top">Measurement point<br>
</td>
<td valign="top">N/A<br>
</td>
<td valign="top">Stop measurement the measurement point
specified by wValue<br>
</td>
</tr>
<tr>
<td valign="top">Set Serial<br>
</td>
<td valign="top">3<br>
</td>
<td valign="top">Low chars<br>
</td>
<td valign="top">High chars<br>
</td>
<td valign="top">Set the 4 character serial of the device.
<br>
<br>
Bottom 8 bits of wValue is ASCII, character 0. Top 8
bits is character 1. <br>
Bottom 8 bits of wIndex is character 2 and top is
character 3<br>
</td>
</tr>
<tr>
<td valign="top">Set Trigger<br>
</td>
<td valign="top">4<br>
</td>
<td valign="top">Measurement point and pin<br>
</td>
<td valign="top">Port<br>
</td>
<td valign="top">Set a trigger on a pin, so that
measurement is automatically triggered on a rising edge,
and stopped on a falling edge.<br>
<br>
Bottom 8 bits is the pin number (wValue).<br>
Top 8 bits is the measurement point number.<br>
wIndex is the ASCII representation of the port (A, B,
C...)<br>
Currently I have only tested this with PA0.<br>
</td>
</tr>
<tr>
<td valign="top">Get Energy<br>
</td>
<td valign="top">6<br>
</td>
<td valign="top">Measurement point<br>
</td>
<td valign="top">N/A<br>
</td>
<td valign="top">Get the accumulated energy figures.<br>
<br>
Returns a 48 byte structure.<br>
<br>
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charset=ISO-8859-1">
<pre style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Courier, monospace; font-size: 12px; margin-top: 0px; margin-bottom: 0px; color: rgb(51, 51, 51); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 18px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div class="line" id="LC107" style="box-sizing: border-box; padding-left: 10px;"><span class="k" style="box-sizing: border-box; font-weight: bold;">typedef</span> <span class="k" style="box-sizing: border-box; font-weight: bold;">struct</span> <span class="p" style="box-sizing: border-box;">{</span></div><div class="line" id="LC108" style="box-sizing: border-box; padding-left: 10px;"> <span class="kt" style="box-sizing: border-box; color: rgb(68, 85, 136); font-weight: bold;">uint64_t</span> <span class="n" style="box-sizing: bord
er-b
ox; color: rgb(51, 51, 51);">energy_accum</span><span class="p" style="box-sizing: border-box;">;</span></div><div class="line" id="LC109" style="box-sizing: border-box; padding-left: 10px;"> <span class="kt" style="box-sizing: border-box; color: rgb(68, 85, 136); font-weight: bold;">uint64_t</span> <span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">elapsed_time</span><span class="p" style="box-sizing: border-box;">;</span></div><div class="line" id="LC110" style="box-sizing: border-box; padding-left: 10px;"> <span class="kt" style="box-sizing: border-box; color: rgb(68, 85, 136); font-weight: bold;">unsigned</span> <span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">peak_power</span><span class="p" style="box-sizing: border-box;">;</span></div><div class="line" id="LC111" style="box-sizing: border-box; padding-left: 10px;"> <span class="kt" style="box-sizing: border-box; co
lo
r: rgb(68, 85, 136); font-weight: bold;">unsigned</span> <span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">peak_voltage</span><span class="p" style="box-sizing: border-box;">;</span></div><div class="line" id="LC112" style="box-sizing: border-box; padding-left: 10px;"> <span class="kt" style="box-sizing: border-box; color: rgb(68, 85, 136); font-weight: bold;">unsigned</span> <span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">peak_current</span><span class="p" style="box-sizing: border-box;">;</span></div><div class="line" id="LC113" style="box-sizing: border-box; padding-left: 10px;"> <span class="kt" style="box-sizing: border-box; color: rgb(68, 85, 136); font-weight: bold;">unsigned</span> <span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">n_samples</span><span class="p" style="box-sizing: border-box;">;</span></div><div class="line" id="LC114" style="box-sizing: border-b
ox
; padding-left: 10px;"> <span class="kt" style="box-sizing: border-box; color: rgb(68, 85, 136); font-weight: bold;">uint64_t</span> <span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">avg_current</span><span class="p" style="box-sizing: border-box;">;</span></div><div class="line" id="LC115" style="box-sizing: border-box; padding-left: 10px;"> <span class="kt" style="box-sizing: border-box; color: rgb(68, 85, 136); font-weight: bold;">uint64_t</span> <span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">avg_voltage</span><span class="p" style="box-sizing: border-box;">;</span></div><div class="line" id="LC116" style="box-sizing: border-box; padding-left: 10px;"><span class="p" style="box-sizing: border-box;">}</span> <span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">accumulated_data</span><span class="p" style="box-sizing: border-box;">;</span></div></pre>
<br>
Have a look at the convertData method in pyenergy.py for
how to convert these figures to real units.<br>
<br>
</td>
</tr>
<tr>
<td valign="top">Map ADC to measurement point<br>
</td>
<td valign="top">7<br>
</td>
<td valign="top">Measurement point<br>
</td>
<td valign="top">ADC<br>
</td>
<td valign="top">Map an ADC to a measurement point.<br>
<br>
ADC = number 0-2.<br>
Probably best not to do this while the measurement is
running<br>
</td>
</tr>
<tr>
<td valign="top">Is running<br>
</td>
<td valign="top">8<br>
</td>
<td valign="top">Measurement point<br>
</td>
<td valign="top">N/A<br>
</td>
<td valign="top">Checks whether the measurement point is
running or not. Useful for when triggers are being used.<br>
<br>
Returns 4 bytes, integer. <br>
1 = Running<br>
0 = Not running<br>
</td>
</tr>
<tr>
<td valign="top">Get number of runs<br>
</td>
<td valign="top">9<br>
</td>
<td valign="top">Measurement point<br>
</td>
<td valign="top">N/A<br>
</td>
<td valign="top">Reports back the number of completed runs
performed. This is mainly a sanity check, so that the
host will know if it has 'missed' a measurement.<br>
<br>
Returns 4 bytes, integer = number of runs.<br>
</td>
</tr>
<tr>
<td valign="top">Clear number of runs<br>
</td>
<td valign="top">10<br>
</td>
<td valign="top">Measurement point<br>
</td>
<td valign="top">N/A<br>
</td>
<td valign="top">Resets the number of runs counter to 0.<br>
</td>
</tr>
<tr>
<td valign="top">Get instantaneous<br>
</td>
<td valign="top">11<br>
</td>
<td valign="top">Measurement point<br>
</td>
<td valign="top">N/A<br>
</td>
<td valign="top">This returns the most recent raw ADC
values for voltage and current. This is useful for
graphs.<br>
<br>
24 byte result structure.<br>
<br>
<meta http-equiv="content-type" content="text/html;
charset=ISO-8859-1">
<pre style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Courier, monospace; font-size: 12px; margin-top: 0px; margin-bottom: 0px; color: rgb(51, 51, 51); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 18px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div class="line" id="LC118" style="box-sizing: border-box; padding-left: 10px;"><span class="k" style="box-sizing: border-box; font-weight: bold;">typedef</span> <span class="k" style="box-sizing: border-box; font-weight: bold;">struct</span> <span class="p" style="box-sizing: border-box;">{</span></div><div class="line" id="LC119" style="box-sizing: border-box; padding-left: 10px;"> <span class="kt" style="box-sizing: border-box; color: rgb(68, 85, 136); font-weight: bold;">unsigned</span> <span class="n" style="box-sizing: bord
er-b
ox; color: rgb(51, 51, 51);">voltage</span><span class="p" style="box-sizing: border-box;">;</span></div><div class="line" id="LC120" style="box-sizing: border-box; padding-left: 10px;"> <span class="kt" style="box-sizing: border-box; color: rgb(68, 85, 136); font-weight: bold;">unsigned</span> <span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">current</span><span class="p" style="box-sizing: border-box;">;</span></div><div class="line" id="LC121" style="box-sizing: border-box; padding-left: 10px;"> <span class="kt" style="box-sizing: border-box; color: rgb(68, 85, 136); font-weight: bold;">unsigned</span> <span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">average_voltage</span><span class="p" style="box-sizing: border-box;">;</span></div><div class="line" id="LC122" style="box-sizing: border-box; padding-left: 10px;"> <span class="kt" style="box-sizing: border-box; color:
rg
b(68, 85, 136); font-weight: bold;">unsigned</span> <span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">average_current</span><span class="p" style="box-sizing: border-box;">;</span></div><div class="line" id="LC123" style="box-sizing: border-box; padding-left: 10px;"> <span class="kt" style="box-sizing: border-box; color: rgb(68, 85, 136); font-weight: bold;">uint64_t</span> <span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">current_time</span><span class="p" style="box-sizing: border-box;">;</span></div><div class="line" id="LC124" style="box-sizing: border-box; padding-left: 10px;"><span class="p" style="box-sizing: border-box;">}</span> <span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">instant_data</span><span class="p" style="box-sizing: border-box;">;</span></div></pre>
<br>
The current and voltage are both fairly noisey, so they
are averaged over the last 32 samples. This provides
much smoother results.<br>
<br>
Have a look at the convertData method in pyenergy.py for
how to convert these figures to real units.<br>
</td>
</tr>
</tbody>
</table>
<br>
I'm not sure how this would be implemented in .NET, however if
there are bindings for libusb, then it boils down to some fairly
easy control transfers. The USB device appears as ID
0xf539:0xf539.<br>
<br>
For example in python:<br>
<meta http-equiv="content-type" content="text/html;
charset=ISO-8859-1">
<pre style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Courier, monospace; font-size: 12px; margin-top: 0px; margin-bottom: 0px; color: rgb(51, 51, 51); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 18px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div class="line" id="LC72" style="box-sizing: border-box; padding-left: 10px;"><span class="c" style="box-sizing: border-box; color: rgb(153, 153, 136); font-style: italic;"># Return whether the measurement point is currently taking</span></div><div class="line" id="LC73" style="box-sizing: border-box; padding-left: 10px;"><span class="c" style="box-sizing: border-box; color: rgb(153, 153, 136); font-style: italic;"># measurements or not</span></div><div class="line" id="LC74" style="box-sizing: border-box; padding-left: 10px;"><span class="k" style="box-sizin
g: b
order-box; font-weight: bold;">def</span> <span class="nf" style="box-sizing: border-box; color: rgb(153, 0, 0); font-weight: bold;">isRunning</span><span class="p" style="box-sizing: border-box;">(</span><span class="bp" style="box-sizing: border-box; color: rgb(153, 153, 153);">self</span><span class="p" style="box-sizing: border-box;">,</span> <span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">m_point</span><span class="o" style="box-sizing: border-box; font-weight: bold;">=</span><span class="mi" style="box-sizing: border-box; color: rgb(0, 153, 153);">1</span><span class="p" style="box-sizing: border-box;">):</span></div><div class="line" id="LC75" style="box-sizing: border-box; padding-left: 10px;"> <span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">b</span> <span class="o" style="box-sizing: border-box; font-weight: bold;">=</span> <span class="bp" style="box-sizing: border-box; color: rgb(153, 153, 153);">self</span
><
span class="o" style="box-sizing: border-box; font-weight: bold;">.<span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">dev</span><span class="o" style="box-sizing: border-box; font-weight: bold;">.</span><span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">ctrl_transfer</span><span class="p" style="box-sizing: border-box;">(</span><span class="mh" style="box-sizing: border-box; color: rgb(0, 153, 153);">0xc1</span><span class="p" style="box-sizing: border-box;">,</span> <span class="mi" style="box-sizing: border-box; color: rgb(0, 153, 153);">8</span><span class="p" style="box-sizing: border-box;">,</span> <span class="nb" style="box-sizing: border-box; color: rgb(0, 134, 179);">int</span><span class="p" style="box-sizing: border-box;">(</span><span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">m_point</span><span class="p" style="box-sizing: border-box;">),</span> <span class="mi" style="box-sizing: border-box; color:
rgb(0, 153, 153);">0</span><span class="p" style="box-sizing: border-box;">,</span> <span class="mi" style="box-sizing: border-box; color: rgb(0, 153, 153);">4</span><span class="p" style="box-sizing: border-box;">)</span></div><div class="line" id="LC76" style="box-sizing: border-box; padding-left: 10px;">
</div><div class="line" id="LC77" style="box-sizing: border-box; padding-left: 10px;"> <span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">running</span> <span class="o" style="box-sizing: border-box; font-weight: bold;">=</span> <span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">unpack</span><span class="p" style="box-sizing: border-box;">(</span><span class="s" style="box-sizing: border-box; color: rgb(221, 17, 68);">"=L"</span><span class="p" style="box-sizing: border-box;">,</span> <span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">b</span><span class="p" style="box-sizing: border-box;">)</span></div><div class="line" id="LC78" style="box-sizing: border-box; padding-left: 10px;"> <span class="k" style="box-sizing: border-box; font-weight: bold;">return</span> <span class="nb" style="box-sizing: border-box; color: rgb(0, 134, 179);">bool</span><span class="p" style="box-sizing: borde
r-
box;">(</span><span class="n" style="box-sizing: border-box; color: rgb(51, 51, 51);">running</span><span class="p" style="box-sizing: border-box;">[</span><span class="mi" style="box-sizing: border-box; color: rgb(0, 153, 153);">0</span><span class="p" style="box-sizing: border-box;">])</span></div></pre>
<br>
Here the code is performing a control transfer on endpoint 0xC1
(indicating there is data to receive, endpoint 0x41 is used when
no data needs to be returned). Request type 8, for "is running",
then the measurement point as wValue. The final parameter
indicates 4 bytes to be returned. This is converted to a
boolean. I suspect it would be similar in .NET.<br>
<br>
The board should be fairly forgiving about the sequencing of
requests sent to it, with the exception that Bad Things will
happen if different ADCs are mapped to the same measurement
point in request 7.<br>
<br>
If anything is unclear, or I've missed out some vital bit of
information, just shout.<br>
<br>
Cheers,<br>
James<br>
<br>
On 06/02/14 09:14, Alex J Lennon wrote:<br>
</div>
<blockquote cite="mid:52F35271.3080806@dynamicdevices.co.uk"
type="cite">
<pre wrap="">Hi all,
Could anybody point me to a breakdown of the comms. protocol between
the data gatherer and the host PC, if there is such a thing?
I'm interested in putting together a simple .NET application, perhaps
involving
ZedGraph, having one foot on the dark-side as it were.
Many thanks!
Alex Lennon
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