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If your RPM shows "dips" (sometimes jumping, usually to 0), use the latest firmware, at least [http://www.vems.hu/download/round/ 2009-10-12] ---- To understand more of the analog and rpm input, a schematic would really help. * the RPM input is divided internally towards 5V, so about 0.6V on RPM input will be about 2.8V internally, equal the RPMref threshold. * RPMref (often around 2.8V), can be changed with pulldown resistor to GND, or pullup to eg 4V ---- == RPM and wheelspeed input == '''Beware that using the RPM input might require input voltage threshold adjustment with a simple pullup / pulldown resistor in some cases, depending on input voltage level. It is easy, but not plugandplay in all cases.''' === RPM input HW === '''rpm_input''' measures 5V if left open * connect the signal input here '''rpm_gndref''' to adjust voltage threshold with pullup/pulldown resistor * Devices with serial_nr >= 100 have appr 0.6V threshold by default that is suitable for the common voltage level thresholds (notably VR / HALL / logiclevel) without pullup/pulldown resistor applied to rpm_gndref. ** pulldown (eg. 100k to GND) for lower voltage threshold (hardly ever needed) ** pullup (eg. 510k to +12V for higher voltage threshold): might be needed in very rare cases when the negative peak of the input signal is higher than +0.55V, like: 2V / 10V squarewave input signal. * devices with serial_nr < 100 measures 2.5V on rpm_gndref input if left open ** if the zero-crossing negative edge is to be detected (standard VR sensor, eg. typical magnetic wheel-speed sensor or 60-2 wheel), leave it open. ** if you want higher threshold, eg. for a 0V / 5V HALL sensor, connect rpm_gndref with a 220k pullup resistor to a 5V (or 510k to 12V) === RPM input config === Known as "RPM settings" in megatune. * rpm_toothcount. The number of pulses per crank rotation. ** 02 for a 4 cyl 2 events per rotation ** 3a (decimal 58) for a 60-2 wheel ** or 23 (decimal 35) for a 35-1 wheel ** set with (Man)mttg19c.. like mttg19c02 or with MegaTune * rpm_multiplier ** set with (Man)mttg1amttc.. like mttg1amttce5 or with MegaTune ** 229 - 0xe5 default for RPM display. Different value can be used to cheat, or for vehicle-speed. The precision is 1 RPM. Note that display from 230 .. 15999 is possible. Above 9999 the first digit is hexa, so * a845 (=10845 RPM) * b231 (=11231 RPM) * c000 (=12000 RPM) * d888 (=13888 RPM) * e792 (=14792 RPM) * f999 (=15999 RPM) * fffu (above 16000 RPM) '''For wheelspeed input''' * set rpm_multiplier=FF (255) first, than adjust according to shown value (calibrate) ** Or you can calculate from the pulses / km. ** '''example: 10 pulses / m = 10000 pulses / km''' *** => 1km/h = 10000 pulses / hour = 166.67 pulses / minute (to be displayed as "0001") *** with tooth_count=0xa7 (decimal 167) *** and rpm_multiplier=0xe5 (decimal 229, same as used for RPM) To support 1 pulse per cam-rotation: experimental [http://www.vems.hu/files/Firmware/Round/round_2005-05-03-doubleRPM_firmwareonly.zip doubleRPM-firmware] * rpm_toothcount=1, rpm_multiplier=229 needed for 1 pulse per camrot. * rpm_multiplier=114 for rpm_toothcount pulse per (crank-)rotation. === RPM tricks === * don't forget to adjust toothcount according to the trigger pattern (pulses per rotation) ** if displayed RPM with toothcount=01 is half of real, see double-RPM experimental firmware that supports 1 pulse every second crankrot (1 every camrot). Normally it shouldn't be needed The sensing '''voltage-level-threshold is adjusted with RPM-gndref pulldown/pullup resistor''' (yes, soldered; not configurable in software) value. Depending on the input signal specs, you might not need to connect RPM-gndref at all (eg. for 5..10V amplitude AC signal). The round device will not be harmed if you first try with RPM-gndref not connected. First measure DC voltage on the output RPM signal (that you want to measure) when connected to nothing, but engine running. '''Measure DC voltage''' * '''between GND and the RPM-input pin'''. With nothing connected expect 4.8 .. 5.2V. * '''between GND and RPM-gndref pin'''. With nothing connected expect 2.4 .. 2.8V ** if the voltage is below 2.6V, you likely need pullup resistor (old standard) ** if the voltage is appr 2.8V, you don't need pullup nor pulldown in most cases. Low amplitude VR-type signal might become more stable with 100..270k pulldown resistor (pulldown means between RPM-gndref and GND). '''Mega Tune Setup''' RPM gauge range (max RPM) can be increased in ''round.ini'' file, change the line: <code> tachometer = rpm, "Engine Speed", "RPM", 0, 8000, 300, 600, 3000, 5000, 0, 0 to tachometer = rpm, "Engine Speed", "RPM", 0, 11000, 300, 600, 3000, 7000, 0, 0 </code> or whatever max RPM you find appropriate if 11000 is not enough. The last values are responsible for the color-"alarms". ----
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