Analog vs Digital Mode on SOLO: When to Use Which

Digital Control and Data Packets in SOLO using USB & UART

Introduction

The same SOLO controller can run your motor in two completely different ways, and picking the wrong one wastes hours. Wire up a potentiometer while the controller waits for digital packets, and the knob does nothing. Send UART commands while the controller reads its analog pins, and your packets get ignored. Both setups look correct on the bench. Only one matches the command mode you actually selected.

This article shows you when analog mode is the right call and when digital mode wins. The short answer: use analog for a standalone motor with no host, and use digital when a microcontroller, PLC, or PC drives the motor and you want telemetry back. The rest is detail.

What Command Mode Means on SOLO

The command mode decides who sets the motor setpoints. It is the single switch between “a voltage on a pin tells the motor what to do” and “a data packet on a bus tells the motor what to do”. Nothing else about the control loop changes. The current loop, the FOC math, and the safety limits run the same way in both modes. What changes is the source of the command.

In analog mode, the controller reads a voltage on its analog input pins and turns that into a speed, torque, or position setpoint. In digital mode, the controller reads and writes registers over UART, USB, or CAN, so a host sets the same values as numbers in a packet. You pick one mode, set it once, and the controller listens only to that source.

Takeaway: command mode is the input source, not the control method. The loop is identical, the way you talk to it is not.

Analog Mode

How Analog Inputs Work

In analog mode, the motor follows a voltage. You feed the SOLO analog input pin a signal between 0 and 3.3 V, and the controller maps that range to your setpoint, low voltage for low command, full voltage for full command. The classic source is a potentiometer wired across the supply and ground, with the wiper going to the input pin. Turn the knob, the voltage changes, the motor responds.

The point of analog mode is that it needs no host. There is no microcontroller, no firmware to write, no protocol to debug. A throttle, a hand-held pot, or a 0-3.3 V signal from another board is enough to run the motor. SOLO can run a full closed-loop FOC setup this way, with a potentiometer setting the command and an encoder or Hall sensors closing the loop, all standalone.

When Analog Mode Is the Right Choice

Reach for analog mode when the application is standalone and the command is naturally a single varying signal. Good fits include:

• A throttle or pedal on an e-bike, scooter, or small EV, where a hall-effect throttle already gives you 0-3.3 V.
• Rapid prototyping, when you want a motor spinning in minutes without writing host code.
• A fixed-function machine that runs one speed or torque set by an operator’s knob.
• Any case where you have a 0-3.3 V control signal from a sensor or another board and no reason to add a bus.

Analog mode is simple and fast to bring up. The trade-off is that one voltage carries one command, and the controller has no easy way to talk back over that pin.

Takeaway: pick analog when a single voltage sets the command and no computer needs to be in the loop.

Digital Mode

UART, USB and CAN Control

In digital mode, a host sends data packets over UART, USB, or CAN to read and write the controller’s registers. Each packet carries an address and a command, so the host can set the speed reference, change the torque limit, switch the control mode, or read back live values, all as numbers. This is the mode you use when a microcontroller, a PLC, or a PC runs the show.

The big win over analog is the return channel. Because the link is two-way, the host does not just command the motor, it reads telemetry back: actual speed, Iq and Id currents, bus voltage, temperature, and fault flags. That makes digital mode the natural choice for closed-loop supervision, logging, and any system that has to react to what the motor is doing. SOLO exposes the same register set across UART, USB, and CAN, so the commands you learn on one bus carry over to the others.

When Digital Mode Is the Right Choice

Choose digital mode when a controller or computer is already part of the system, or when you need more than one command at a time. Typical cases:

• Integration with an MCU, PLC, or PC that runs your application logic.
• Telemetry and logging, where you need actual currents, speed, and faults streamed back.
• Multi-axis setups, where one CAN bus addresses several SOLO units on the same wire.
• Automation, where setpoints, limits, and modes change during a run without a person at a knob.
• Switching between torque, speed, and position control on the fly. See torque, speed and position control for how the modes differ.

Digital mode costs a little more setup, you need a host and you write some code, but it pays back in precision, visibility, and control.

Takeaway: pick digital when a host is in the loop, when you need telemetry, or when one command is not enough.

Side-by-Side Comparison

Here is the quick decision table. Map your project against each row and the mode usually picks itself.

Takeaway: analog wins on simplicity and cost, digital wins on precision, telemetry, and scale.

Switching Command Mode in Motion Terminal

You set the command mode in the SOLO Motion Terminal, the same place you configure the motor and the control loop. The mode is a single parameter. Connect to the controller, pick analog or digital as the command source, and write it to the device. From that point the controller listens only to the source you chose, so a pot will not move a motor set to digital, and packets will not move a motor set to analog.

If you are setting the controller up for the first time, it helps to confirm the command mode as part of the wider configuration, motor type, sensor, control mode, and limits, rather than in isolation. You can also watch the result live: in digital mode the Motion Terminal reads telemetry back while you command the motor, which is the fastest way to confirm the mode took effect. See monitoring mode on SOLO for how that live view works.

Takeaway: command mode is one parameter in the Motion Terminal, set it once and the controller obeys only that source.

Pros, Cons & Trade-offs

Neither mode is better in the abstract. They solve different problems, and the right pick depends on whether a host is in your system and how much you need to see back from the motor.

Analog mode

• Pros: simplest to wire, lowest hardware cost, runs standalone, brings a motor up in minutes with no code.
• Cons: precision is limited by signal noise and ADC resolution, no telemetry over the command pin, one signal carries one command, awkward for multi-axis.

Digital mode

• Pros: exact numeric setpoints, two-way telemetry, several axes on one CAN bus, full automation and on-the-fly mode changes.
• Cons: needs a host (MCU, PLC, or PC), more setup and some code, slightly higher cost to get started.

The trade-off is rarely close once you ask one question: is there already a computer in the loop? If yes, digital almost always pays back its setup cost in precision and visibility. If no, and a knob or throttle is enough, analog keeps the system lean. A common middle path is to prototype in analog to get the motor turning, then move to digital once the application logic and telemetry matter.

How SOLO Supports Both Command Modes

SOLO controllers support both analog and digital command modes from the same hardware, so the choice stays a configuration setting rather than a hardware commitment. You can wire a potentiometer to the analog inputs for a standalone build, or talk to the controller over UART, USB, or CAN when a host drives it, and switch between them in the Motion Terminal. The same controller that runs a throttle-driven prototype today can move to a CAN-based multi-axis system later without new hardware. You can explore the workflow on the SOLO Motion Terminal page.

Conclusion

Command mode comes down to one question: who sets the setpoint. Use analog mode when a voltage from a pot, throttle, or sensor is enough and the motor runs standalone with no host. Use digital mode when a microcontroller, PLC, or PC is in the loop and you need precise setpoints, live telemetry, or several axes on one bus. Both run the same control loop underneath, so you are picking an input source, not a different motor controller. A good way to start is to prototype in analog, then move to digital as your automation and logging needs grow. When you are ready to set it, the SOLO Motion Terminal is where you choose the mode and confirm it works.

FAQ