Radio | Speed Controller (ESC) | Servo Output | Input/Output - GPIO | General Configuration | Programming
Micron receivers implement a set of features for model rail
locomotives and land-based vehicles.
The majority of features are common to all receivers, but some will
be specific - refer to a receiver's user manual and programming table for details:
Although most users will not need
all functionality, it is there and easily accessed
by programming the receiver.
Each receiver is configured with a default set of features which is described
on the receiver's web page and in the user manual for the receiver.
Most receivers contain 4 pre-set configurations which can be selected
using a power-on jumper or by programming the receiver (see the user manual for details).
Different configurations are always available to special order
- contact us.
The radio part of the receiver is responsible for connecting with a transmitter
and decoding the control data.
Some receivers have a separate RF module with its own LED to indicate signal
quality, others integrate the RF and receiver behaviour into one chip with
a common status LED.
Almost all Micron model rail and land vehicle components use the
Spektrum DSM2/DSMX protocols which gives access to a wide variety
of 3rd party products.
it also means that a Micron receiver can be used with any real Spektrum
or third party transmitter that implements the Spektrum protocols.
This includes all Micron model rail transmitters.
DSM2/DSMX uses a spread-spectrum type radio protocol where the
contol information is 'encrypted' using the transmitter ID. Thus, only a receiver
which has stored a transmitter's ID is able to decode the control data.
That is how many R/C systems can be used within a small space without
interferring with each other.
The controls on a transmitter (knobs, switches, push buttons, joysticks, ...)
are encoded into separate R/C channels which are combined into the radio signal.
The way that this is done is called the 'over-the-air protocol' - e.g
DSM2 and DSMX. The channels are numbered (ch1, ch2, etc) and are
represented as a digital value, usually 0..1023 but can be a higher precision
0..2047 or 0..4095.
The association of transmitter control to R/C channel convention for a model
aircraft transmitter is:
The association of control to R/C channel mapping for Micron model
rail transmitters is described in the user manual for each transmitter.
All of them provide these common mappings:
|ch2:||Selecta (if implemented on that transmitter)|
|ch3:||direction (if low-off throttle) or auxiliary functions|
Micron receivers have a variety of outputs, each type is denoted by
a letter (H, F, P, etc):
The receiver firmware associates each of these outputs with a
R/C channel so that changing values on the channel (i.e. moving
the transmitter control) affects the output state.
For example, R/C ch1 is usually mapped onto H1 so that the transmitter
throttle/regulator knob changes the motor speed.
The mapping for each output is independent and
multiple outputs can use the same R/C channel.
- H: one or more fwd/rev motor speed controllers
- F: switch (usually 2A capable), used as an
on/off switch to control an external device (e.g. high current LED,
smoke generator, ...) or with PWM as a single direction motor
speed controller or light dimmer
- P: low current logic level, usually 0V when off and 3.3V when on;
used to control low-current LEDs or can output a servo signal
Receivers are provided with a set of predefined R/C channel to
output mappings - the configuration. Most receivers have 4
selectable configurations for common usage.
BINDING WITH A TRANSMITTER
A receiver has to be linked to a transmitter before it can be used.
This process is called 'binding' and involves the transmitter
transferring a piece of data (the ID) to the receiver which the receiver uses
to identify 'its' transmitter and ignore all others.
Binding has to be done only once, unless you need to change to
a different transmitter - in that case, you simply bind to the new transmitter.
A transmitter can be bound with any number of receivers, so long as they
use compatible protocols, but a receiver can normally be bound to only
All receivers will respond to the transmitter,
so only one receiver should normally be switched on at any time.
An exception to this is for receivers and transmitters that support
the Selecta feature (all Micron receivers
support Selecta and some of the Micron transmitters
also support Selecta).
The general process for binding is:
- receiver is placed into bind mode - usually indicated by
a rapid LED flash
- the transmitter is then switched on in bind mode - the method
for doing this varies, refer to the transmitter manual
Most Micron receivers support manual and auto binding:
Manual Bind: either a jumper plug is inserted or
2 pads must be connected and then the receiver switched on. The receiver
enters bind mode immediately and the jumper or pad connection
can be removed.
Auto Bind: the receiver enters bind mode automatically
after a few seconds if it is unable to find a previously bound transmitter.
'SELECTA' OR LOCO SELECTION
Selecta allows receivers to be made active or inactive from the transmitter.
This allows the number of functions controlled to be expanded
using two or more receivers, or allows multiple models to have
control switched between them.
Selecta uses one of the R/C channel (default 2), to carry the selection
data; only when a receiver gets its selection code does it respond to the
Selecta enabled transmitters have a 12-way rotary switch for controlling the value
(i.e. code) sent on the Selecta channel.
A receiver's Selecta code is store during bind.
Simply rebind if you need to change Selecta switch position for a model.
The default receiver action when deselected is to maintain all outputs,
including the speed controller, at the current setting.
This is useful on a continuous run type layout allowing a deselected
loco to continue running. The deselection behaviour can be changed to
stop so that the loco decelerates smoothly to a stop when deselected
- see the programming table for your receiver for details on how
to change the Selecta behaviour.
Micron receivers have at least one integrated
bi-directional ESC (Electronic Speed Controller)
for brushed motors. Some receivers also support the connection of
an external ESC for either brushed or brushless motors - this is done
by configuring an output as a SERVO-ESC.
MOTOR CONTROL, CENTRE-OFF
One R/C channel is used to control the motor in both directions.
With a rotary control, centre is off, left is reverse, right is forward.
With a joystick transmitter, up is forward, down is reverse.
MOTOR CONTROL, LOW-OFF
One R/C channel is used to control the motor speed and another
R/C channel is used to control motor direction: the default is ch1 and ch3.
Direction can be changed at any time but only takes effect when the throttle
is closed. On a joystick transmitter, direction is usually the elevator control
which is self-centring; the stick is simply pushed in the desired direction
and then released. Model rail transmitters either have a toggle switch
or a rotary control (e.g. Tx24v2) for direction.
MOTOR CONTROL, CENTRE-OFF SPLIT
This is like low-off with separate speed and direction controls, but
the output is connected to an external forward/reverse ESC.
This is useful for large battery electric locos where the operator
prefers low-off control for compatibility with their live-steam locos.
ESC START/MIN POWER
The motor power level can be made to go quickly to a minimum value
as the throttle is opened. It can be set from 0 to 100% and is useful
when a motor requires a high starting voltage.
The default is 0%.
ESC MAX POWER
The maximum power level available at full throttle can be reduced;
the reduced range is spread over the full throttle control.
This can be used to match engine speeds for a consist or to reduce
the maximum speed of an overpowered vehicle or when children are
controlling the locomotive.
The maximum power can be set from 0 to 100%, the default is 100%.
ESC PWM FREQUENCY
Motor speed is controlled using Pulse Width Modulation (PWM). This works
by rapidly switching the motor voltage on and off, the ratio between
on and off giving an effective lower voltage.
The PWM frequency can be varied by programming a receiver; the default
is the maximum supported by a particular receiver (usually 16kHz, which
is silent). Lower frequencies produce more torque but the motor runs
less smoothly and can make a noise if the frequency is within hearing range.
The motor rotation direction can be reversed by programming the receiver.
This can be useful if the motor has been wired incorrectly or
to make a temporary change when a locos are coupled into a consist.
Reversing motor direction does not change the directional lighting operation.
ESC SOFT START/STOP (INERTIA)
Soft start/stop alters the rate of acceleration and deceleration.
It can be used to simulate the inertia of a heavy train when moving off
or its momentum when slowing down. Many Micron transmitters include an
inertia facility which is applied equally to start and stop.
Micron receivers have an inertia function which can either be
the same for start/stop or specified separately for start and stop.
In order to prevent a model moving off as soon as a receiver is switched
on, the speed controller is disabled until an off/stop throttle signal
The speed controller will be disarmed should any of LVC,
Emergency Stop, or Sleep conditions be triggered.
THIS IS A SAFETY FEATURE AND DISABLING IS DISCOURAGED.
Any P output can be configured as a servo with the normal 1ms-2ms pulse
width signal repeated every 20ms. For rotary or stick-type transmitter
controls, the position of the servo arm is proportional to the position
of the controlling channel. Transmitter push buttons and toggle switches
may also be used to control a servo output, in this case the servo arm
moves immediately to the low, mid or high position as specified
in the transmitter user manual.
Many Micron receivers have a 3.3V output which can be used to power
a small servo.
The maxium current is usually limited to no more than 200mA - see
the receiver user manual for the specific max current.
This is normal servo operation where the rotation is directly proportional
to transmitter control movement.
Servo rotation speed can be slowed by programming the receiver.
Speed setting '1' is normal, settings 2 to 6 make the servo move more slowly;
the actual speed depends on the type of servo.
This is a P output connected to an external ESC.
maps this to a virtual ESC (aka throttle) so that changes to the ESC
behaviour (centre-off, split, inertia, emergency stop, etc) affect the
servo output signal.
This feature supports servos on 2 P outputs with travel controlled by
the mixing of 2 R/C channels.
A typical use is to drive 2 external ESC mixing throttle and steering R/C
channels for differential steering on a boat or tracked vehicle.
This feature gives full servo proportional travel over half transmitter control movement.
It is useful for controlling 2 servos from one R/C channel; one servo moving
for control value low to mid and the other moving for mid to high.
The servo moves over its full travel when the transmitter control is set
low or high. When the control is centred (mid value), the servo is at the low
end (1ms) of its travel; when the control is low or high, the servo is at
the high end (2ms) of its travel.
The servo end points can be adjusted using
Servo Travel Adjustment.
SERVO TRAVEL ADJUSTMENT
Servo throws (low and high end points) can be adjusted using a transmitter,
the servo centre position will always be at the mid-point of the low and high travel. To adjust a servo, the servo output is selected first and then the travel adjusted using
either the throttle control or direction toggle if the throttle servo is being adjusted.
One servo output may be adjusted at a time. The output is first selected by
programming and then the transmitter control is used to increase or decrease
the servo throw:
Consult the programming table for the program
sequence to access servo adjustment, enter this sequence and then:
- R/C channel 3 (toggle switch on most Micron transmitters, elevator on
stick type transmitters) is used for most outputs
- R/C channel 1 (throttle) is used when adjusting a servo on R/C channel 3
- within 5 seconds, move the control for the output being adjusted to the end that needs adjustment
- increase or decrease the servo end-point:
- on Micron or stick type transmitters, use the throttle control if a
servo on R/C channel 3 is being adjusted:
- hold throttle knob fully CCW or throttle stick at low throttle
to decrease travel
- hold throttle knob fully CW or throttle stick at high throttle
to increase travel
- use the direction toggle, reverser control or elevator stick for
servos on all other R/C channels:
The receiver LED will flash twice per second as the servo travel is
being adjusted and stop flashing when the limit is reached.
Take care: the servo may reach its mechanical stop before the increase
side adjustment limit is reached.
- hold toggle down, reverser to REV or elevator stick
down to decrease travel
- hold toggle up, reverser to FWD or elevator stick up
to increase travel
- move the servo control to the opposite side if you also
need to adjust that end-point
- centre both controls to finish the adjustment, the receiver will
return to normal operating mode after the control
corresponding to the P port being adjusted has been centred for 5 seconds.
Go through the above steps to adjust a different servo output pin.
Receivers have a number of general purpose input and outputs (GPIO) ports, mostly used
There are 2 types:
- P - these are logic level outputs that can supply a low current
(typically 20mA max), 0V when off and 3.3V when on. They can be used
to power LEDs via a series resistor suitable for the desired LED current
and for driving servos where the P pad provides the control signal to
the white or yellow wire of the servo lead. Some receivers are able to provide
3.3V to micro servos, larger servos must be powered from a separate source
- e.g. a 5V regulator connected to the battery.
P pads can also be used for input - e.g. shuttle control, remote sensors;
see the receiver user manual for information.
- F - these are switches and can control up to 2A; they are open
when off and connected to negative when on.
For programming, F switches are given numbers sequentially after all P outputs,
e.g. if a receiver has 6 x P and 4 x F, the F outputs are numbered 7 to 10.
For compatibility with Deltang receivers, F outputs are also labeled with letters,
e.g. F1 is A, F2 is B, etc.
Momentary outputs are activated when a transmitter control is at the specified value.
They can be set normally on or normally off and switched to the opposite
by the transmitter control, e.g.:
- prog 3,4,1,5,1 = P4, normally off, on when Ch5 is low
- prog 3,6,1,3,6 = P6, normally on, off when Ch3 is high
LATCHING ACTION - TYPE 1
Outputs switch state (toggle on and off) each time the transmitter control
is actioned. Most transmitter controls may be set to low, mid and high values
and this allows them to control 2 outputs - one toggled at low and the other
toggled at high. The initial output state can be set to on or off.
LATCHING ACTION - TYPE 2
This feature uses time as well as control value to toggle up to 4 outputs:
2 outputs are toggled by control actions < 1 second and another 2 outputs by control
actions > 2 seconds.
The initial state of all outputs is off.
Outputs may be assigned as front, rear, brake and reversing lights.
They are controlled by the state of the speed controller (or servo output
for type SERVO-ESC).
Front and rear lights are switched based on motor direction. Both start off
and either the front or rear light is switched on when the throttle is opened
for the first time and stays on when the loco/vehicle stops, changing
when the motor direction is changed.
The brake light comes on briefly when the motor stops. The on duration defaults
to 1 second and can be set using one of the General Configuration program options.
The reverse light is similar to the rear light and is on when the motor
is moving in reverse. It goes off when the vehicle stops.
All auto-light action can be disabled and enabled using a transmitter
control by programming the receiver.
This feature is off by default and can be configured by programming the receiver.
This section comprises a collection of functions that apply to the
receiver as a whole.
The LED on the receiver indicates the state it is in but it cannot be seen
if the receiver is enclosed within a model.
LED2 allows another LED attached to one of the P or F outputs to mirror
the onboard LED.
As this second LED may also be used for directional lighting, the default behaviour
is to stop mirroring once the speed controller arms; thus, the front light
on a vehicle or loco can show what the receiver is doing as it starts up,
during bind, while programming and then operate as a front light
in normal use.
LED2 mode options:
- normal (as described above)
- as above including when deselected
LOW VOLTAGE CUT-OFF (LVC)
The receiver provides low voltage detection to protect batteries that
must not be discharged too far; these are mostly lithium based (LiIon or LiPo).
The receiver cuts power and disables the motor when the voltage falls too low.
As the battery voltage will usually recover when the load is removed,
the motor may be restarted by closing the throttle and re-opening.
This should not be done too often as the battery is near exhaustion and should
The LVC trigger point is set automatically based on the battery voltage
measured on start-up.
The trigger threshold can also be set automatically in 0.1V increments with
a minimum of 2.5V.
- 3V for < 6V at start-up
- 6V for 6V to 9V
- 9V for 9V to 12V
- 12V for 12V and above
Receivers also have an 'L' input which is used when an external booster module
is used to raise a low voltage battery to a higher voltage (e.g. single LiPo
cell to 12V).
The 'L' input takes priority over the main positive pad.
The receiver will go into sleep mode if the throttle is not moved for
an extended period - the default is 1 hour and can be programmed up to 6 hours
The receiver must be switched off and on again to get out of sleep mode.
Although the receiver draws a low current in sleep mode, this is not a
substitute for an on/off switch.
Sleep mode can also be configured to be activated after the LVC has triggered.
When enabled, the receiver goes into sleep mode 5 minutes after LVC to avoid
further draining the battery.
CRUISE / FAILSAFE
Cruise control keeps the motor running if the transmitter signal is
lost - e.g. if the loco goes through a tunnel or behind a large bush.
If cruise control is disabled, the receiver enters failsafe mode
several seconds after no signal.
Failsafe stops the motor and can be used as a form of emergency stop.
The default configuration for all receivers has cruise control enabled
'cruise control' and allows the loco to keep running if the transmitter is
The cruise control / failsafe mode can be set either using
a power-on change or by programming.
The emergency stop function uses a transmitter control to rapidly bring
all vehicles controlled with that transmitter to a halt.
The throttle must be closed and the triggering control released to
start the motor again.
When arming is enabled, the speed controller will not start the motor
until a 'off' throttle signal is received.
This is a safety feature and should not be disabled unless really necessary.
Selecta allows receivers to be made active or inactive from the transmitter.
Selecta operates using one of the R/C channels (default is 2);
the value of which is stored by a receiver when bound.
During normal operation, a receiver responds to
transmitter controls only when the received Selecta channel value matches
its stored value, +/- a small delta.
The default action when deselected is for the motor to continue running
at the last setting; this is appropriate for a continuous loop type layout.
This behaviour can be changed to stop when deselected by programming
BACKUP AND RESET CONFIGURATION
Configuration data is stored in non-volatile memory - a type of stable storage
that is retained when the receiver is not powered. Any changes you make, either
using a power-on change or by programming, is also written to the memory.
When the receiver is first powered, or when an alternative configuration is
selected, the data is also written to a backup store.
A reset (power-on change or programming) copies the backup data over the top
of the current configuration; thus any modifications are are lost.
You can update the backup at any time by programming.
Receivers contains several alternative configurations - a preset collection of
features. These can be selected by a power-on jumper setting or by programming
the receiver. Once selected, the receiver will use that configuration
each time it is powered on; any changes made to the previous configuraion
(e.g. by programming) are lost when an alternative configuration is selected.
See the receiver user manual for details of the configurations.
The receiver firmware version comprises 2 numbers separated by a dot (e.g. 1.6). This
will be written onto the receiver label or, if no label, onto one of the larger chips.
If this information is lost (or rubbed off the chip), the program
sequence 4,14 can be used to display the version as 2 sets of repeated LED flashes:
1-flash 6-flash, for 1.6.
Receiver behaviour can be changed using the transmitter to which the receiver is bound.
The receiver must first be put into programming mode and then the
direction toggle switch, or reverser knob on Tx24v2, or elevator on a stick type
transmitter, is used to enter a program sequence one digit at a time.
The receiver LED (and LED2 if enabled) flashes to indicate the
value of the current step in the programming sequence.
For example, if the current value is 4, the CPU LED flashes 4 times, pauses
and repeats - this is called a 4-flash.
Where it is possible for the current value to be zero (e.g. low voltage
cut-off tenths), this is shown as a single brief flash much shorter than the
normal value flash.
The receiver feature set and, hence, the programming table is large.
It is presented in a separate document
which lists all functions that may be changed by programming.
The table is split into 5 blocks of related functions each with the same value in
the first column.
The table columns contain the program values which must be entered to change
a particular function. For example, to change the throttle behaviour
from centre-off (forward and reverse on one control) to low-off
(separate throttle/regulator and direction/reverser controls)
the program sequence 1, 1, 2, 1, 3 is entered. Each digit of this
program sequence is taken from the columns, left to right:
1 = ESC Configuration
1 = H1 (most receivers contains only only 1 ESC)
2 = Low Off Throttle
1 = Throttle on R/C channel 1
3 = Direction control on R/C channel 3
One function can be changed at a time. The general method is:
- set receiver into programming mode
- enter a program sequence
- repeat until all programming changes have been made
Enter Programming Mode
There are 2 methods of getting a MR6xx receiver into programming mode:
- hold the transmitter channel 2 and channel 4 controls at
high or low extremes and then switch the receiver on;
these are the F1 and F2 buttons on a Tx20v2
and the Selecta switch and S2 button on a Tx22X;
the receiver LED will flash rapidly shortly after switch on,
centre one or both channel 2 & 4 controls (e.g. release the buttons
on Tx20v2 or the S2 button on Tx22X)
- switch the transmitter and receiver on (they must be bound),
wait 5 seconds without touching any controls and then tap out morse
SOS (... --- ...) on the transmitter bind
button (or toggle the gear switch high to low for a stick transmitter);
- dots (…) will be a quick press of the button and must be
less than 1 second in duration
- dashes (---) must be greater than 1 second and shorter
than 5 seconds – 2 seconds is a reliable time
- the time between each dot or dash must be less than 5 seconds
When programming mode has been successfully entered, the receiver LED
will show a 1-flash - this is the 1 from the first column
of the programming table.
If you do not get the 1-flash, repeat the procedure to enter
programming mode. It usually takes a couple of
attempts to get the SOS method correct if you have never done it before.
Enter a Program Sequence
One programming change requires up to five choices to be made.
These are called 'levels' and each has several options.
They are documented in the programming table.
Completion of a programming change exits programming mode and requires the
receiver to be placed into programming mode again for the next change.
It is a good idea to write the programming sequence on a piece of scrap
paper and cross off each digit as it is entered so that you
don't lose track of where you are in the sequence.
You always start at the top of the first column and 1-flash is
displayed on entering programming mode.
- The flash count for a level is incremented by setting the
R/C channel 3 control low and back to mid.
- The flash count for a level may be decremented by holding
the R/C channel 4 control low while operating the R/C channel 3
control; R/C channel 4 is available on some Micron transmitters
- e.g. F2 on Tx20v2 and S2 on Tx22X and Tx42v2
- The level value is accepted and the flash count for the next
level is displayed by setting the R/C channel 3 control
high and back to mid.
Most Micron transmitters have a toggle switch on R/C channel 3
which is marked A/B, or forward/reverse for a low-off transmitter:
Always return the toggle switch to centre after pushing down or up.
Refer to the transmitter user manual for specific information
on the R/C channel 3 control - Tx24 has a rotary reverser control.
- pushing the switch down (or toward 'reverse' for a low-off transmitter)
sets the R/C channel to a low value and increments the flash count,
- pushing the switch up (or toward 'forward') sets the
R/C channel to a high value,
accepts the flash count and moves the program sequence
on to next level or exits programming mode if the current level is
the last in the sequence.
The receiver LED will flash rapidly while R/C channel 3 is high or low and
then return to a slower repeated flash when the control
is back to the middle.
After accepting the flash count for a level, the receiver LED displays
a flash count for the current value of the next level. This could be
higher than 1-flash if the function is set in the receiver configuration
or has been previously programmed. For example:
- the default Selecta R/C channel is 2, so a 2-flash will be
displayed after entering 4,8,2
- P1 is configured as a front light, so a 4-flash will be
displayed after entering 3,1
When the last level for a sequence has been accepted, the receiver LED
will light continously and the receiver is back in normal operating mode.
The maximum number of levels is 5, but not all sequences use all 5;
if level 5 in the table is blank, the CPU LED will light continously
after level 4 is accepted.
Programming changes are accepted only when the receiver LED lights solid
at the end of the sequence.
If a mistake is made mid way through a sequence,
switch the receiver off to abort.