Hardware Overview - Kestrel280/MZST GitHub Wiki

The Z-Speed system is split up into four modules. A transmitter module, receiver module, a sensor module, and a feedback module. The receiver, sensor, and feedback modules are combined currently, but the logic is split up in a way such that it will be easy to separate them as more input and output devices are adopted.

Receiver/Sensor/Feedback Module

MZST_Rev_3_2025-May-22_03-52-small

Each receiver module is built around an ESP32-S3 and a RXM-433-KH3. The built-in feedback module is a 5V RGB LED strip driven by MOSFETs, as well as an 8-ohm speaker driven by an LM386 audio amplifier. The audio has an enable feature to cut down on unwanted noise during startup and shutdown. The "sensor module" is a capacitive touch sensor driven by a built in touch pin of the ESP32-S3. The electrode is the metal shell of the module.

Part of the way that Z Speed achieves such exceptional accuracy and precision is a low-drift TCXO, the SIT1566. This is hooked up to the 32K RTC pins of the ESP32 (IO15 and IO16). The clocks of all receiver modules are also synchronized as often as possible by the RF system. The RF system has a baud rate of 4600 and due to the packet construction there is a ~35ms propagation delay (see references for details). The data pins and the VT pin will be held high for 130ms after there is no more valid data being received. Despite the propagation delay, this system makes for excellent synchronization -- the encoders/decoders are entirely hardware based, so there will be very little discrepancy between modules (<100us).

The ESP32 connects with a w.FL/MHF3/IPEX3 Connector, and the 433MHZ RF module uses a standard 50 ohm SMA connection.

When looking at the "front" of the board (into the USB-C connector) the BOOT button is on the right, and the RESET button is on the left.

Schematics

Receiver Module

Screenshot 2025-05-22 110520

Feedback Module

Screenshot 2025-05-22 114459

Pin definitions

Feedback

RED_PIN 2
GREEN_PIN 3
BLUE_PIN 4
AUDIO_PIN 1
AUDIO_EN_PIN 5

Sensor

CAPSENSE_PIN 7

RF Receiver

RF_VT 45
RF_D0 42
RF_D1 41
RF_D2 40
RF_D3 39
RF_D4 38
RF_D5 37
RF_D6 36
RF_D7 35

Transmitter Module

The sole purpose of the transmitter module is to send RF blasts to synchronize the clocks of the receiver modules as often as possible.

The transmitter module is comparably very simple, it is based on a Xiao ESP32-S3 module, along with a TXM-433-KH3. It also breaks out leftover I/O pins to a button, and an LED for testing and debugging purposes.

The ESP32-S3 uses a u.FL connector and the RF connector is a standard 50 ohm SMA.