iSV57 servo communication
On the topside of the iSV57 servo, the RS232 port can be found, over which the ESP can obtain servo states and parameterize its settings.
To communicate with the servo via the RS232 port, the communication structure was reverse engineered.
The picture below shows the voltage over time of the servos Rx (channel 1) and Tx (channel 2) ports, probed while the ESP was connected
The osciloscopes settings are:
5V/div
5ms/div
One can see, that the channels have low levels of -5V and high levelsd of +5V. The latency between the end of a hosts Tx burst (channel 1) and the start of the clients burst (channel 2) was up to 3.5ms.
The analog signals form a serial communication, which can be analyzed and decoded with, e.g. sigrok.
An example of the decoded bursts is shown below
The picture was taken in sigrok, where the modbus decoder was selected with the setting as shown below
With some knowledge about the data structure and the register addresses, the numbers can be interpreted like such
