Common elements
STEP400 and STEP800 are similar boards and have the following parts in common
- Based on Arduino Zero (ATSAMD21G18A)
- Uses W5500 for Ethernet controller
- Motor drivers with built-in motion controller from STMicroelectronics
- Type and shape of input/output terminals
- DIP switch, microSD card slot
Although the motor driver chips are different, they belong to the same series by the same manufacturer, and the overall structure and instruction system are quite similar.
Different elements
| STEP400 | STEP800 | |
|---|---|---|
| Number of axes | 4 | 8 |
| Motor Driver | PowerSTEP01 | L6470 |
| Input Voltage | 12-72V | 9-32V |
| Maximum phase current (under ideal conditions) | 5A | 3A |
| Sensor inputs terminal | HOME, LIMIT | HOME |
| Voltage drive mode | Yes | Yes |
| Current drive mode | Yes | No |
There is a big difference between STEP400, which has a small number of motors that can be controlled (number of axes), but can drive larger motors, and STEP800, which has a large number of axes but cannot drive larger motors. Also, current mode is only available for STEP400. Current mode is simply put, it is a motor driving method that can rotate up to high speed range, although it makes more noise when driving. The voltage mode is suitable for quiet, clean rotation in the low speed range.
Which to choose
STEP400 
STEP800
PowerSTEP01 used in STEP400, has almost all the functions of L6470 used in STEP800, and is upward compatible in terms of functions. However, if you look at it in detail, it has some inferiorities, such as low resolution of stall detection threshold, but you can use PowerSTEP01 for any motor that can be turned by L6470.
Generally speaking, STEP400 is more versatile in a wide range of situations and can drive motors of all sizes, while STEP800 can be very useful when you have a specific project in front of you that requires a large number of motors to be run.