Available on Github.
I had to make a new iteration of my alternative electronics hat for the Turtle Rover. On the former revision G I run into trouble with external I2C due to level shifting issues. Took the chance to simplify the circuit and route I2C and RS232 directly to the Raspberry Pi header instead through ARM micro-controller. So the server software can directly access any external peripherals through kernel drivers. Hardware description available on Github.
In addition I created a experimental motor driver board with dual ST L6206 DMOS full bridge driver as a direct drop-in replacement for the L298.
Both, the BQ40Z80 battery management system and long range RC receiver are connected by I2C/SMB, routed to Turtle Rover electronics hat. That allows readout of all battery parameters as well as RC receiver parameters like link status, link quality, channel values etc. Hence a fully transparent and monitorable system. There is a provision for RS232 that may connect additional equipment inside the box to the electronic hat in the future (e.g. GPS).
The external charger or power socket has a direct battery management system connection. That allows an external power supply to charge the battery or power the entire Turtle Rover, e.g. from a solar panel or auxiliary battery. But external equipment (top mount) can also draw battery power for its own supply.
Additional press nuts on the rovers rear bracket allowing easy installation of equipment on top and in combination with the main bracket fix points.
The WLAN cable uses a U.FL (IPEX) connector for a direct connection the modified Raspberry Pi 3 with external antenna socket. This way, no additional WLAN module is required.
In difference to the original Turtle Rover battery I run a custom battery pack in a 6S3P configuration of Samsung 18650-35E cells. That’s 22.2V/10.2Ah in total. The brand new, yet to be released, Texas Instruments BQ40Z80, a 2 to 7 series battery pack manager with impedance track gas gauge, takes care of the entire pack. Its protection and balancing features guarantee safe handling of this energy source. The SMBus interface allows readout and indication of all battery lifetime parameters in the Rovers mission control software.