Changes between Version 11 and Version 12 of WikiStart

Timestamp:

Jul 31, 2019, 5:32:05 PM (5 years ago)

Author:

bouyer

Comment:

--

WikiStart

@@ -1 +1 @@
 = A low-cost SoC power measurement platform =
+[[PageOutline]]
 
 Evaluating software impact on power consumtion is not easy. Using a simple multimeter on the power line is not accurate enough because there are big variation in input current. A higher sampling frequency is needed. Also you have to correlate the power data with the various phases of a software (separate initialisation from the computation part for example).
@@ -64 +65 @@
 
 [[Image(v_o.gif, 50%, title="tension to ADC outut",longdesc="tension to ADC output")]]
+
+== version 2 ==
+The version 2 of the hardware got several improvements:
+- as the USB part of the pic18 is not used, we switched to a pic18f27j13
+- There are now 8 GPIOs available
+- a 4th current range (up to 5A) has been added
+- The USB/serial part is electrically decoupled from the target board, to avoid
+  possible ground loop affecting current values. The USB/Serial bridge is
+  powered from USB, while the pic18 is powered from the load power supply.
+- The pic18 can power on or off the load
+- the pic18 controls two solid state relays, which can drive e.g. power or 
+  reset switches for the target board.
+- the pic18 has one optocoupled input, which can monitor e.g. a power led
+  from the target board.
+- a second serial port is available from the pic18, which can be used to
+  connect to a TTL-level serial console on the target board, avoiding an
+  extra serial/USB converter.
+
+The software also got major reworks. To use the new features, a bidirectionnal
+connection is now needed. We also used this opportunity to store calibration
+value in the pic18's flash, so we don't need to match a board with its
+calibration values on the host's side.
+The USB/serial port of the board runs at 921600 bauds. The board accepts the
+following commands from the host:
+- '''B<n>''' connect to the target's serial port at speed ''n''. If ''n'' is
+  ommited, use the previously set speed. exit with ''#.''
+- '''C''' get calibration data.
+- '''C<string>''' set calibration data string. It is just a string stored
+  in flash and echo'ed back on request; it's up to the host software to
+  interpret it. In order to keep the firmware simple, the string has to be
+  exactly 83 char longs, and can hold only digits, . or spaces.
+- '''E''' causes the firmware to exit, resetting the pic18
+- '''Mn''' with ''n'' being 1 or 0: start or stop measures.
+- '''Pn''' with ''n'' being 1 or 0: power on or off the load
+- '''Rn''' with ''r'' being 1 or 2 and ''n'' being 1 or 0: turn on/off relay
+  ''r''.
+- '''S''' get various input states
+
+Each command is replied with '''OK''', unless and error occured.
+
+Host software getting values from the board now has to start measures
+with '''M1''' first; it should also send '''M0''' before exiting.