Charge Cable and Supplied Battery

The supplied USB to 9v barrel-jack is rated for 5v on the USB end, and outputs 9v on the barrel jack, centre pin positive. The supplied rechargeable LiPo battery has a nominal charged voltage 8.4v. The battery’s capacity is 1400mAh.

The supplied cable can provide adequate voltage to charge the battery through rick, but using an equivalent mains-powered 9v DC charger the battery can charge faster. For the fastest charging an external LiPo battery charger, commonly used for Remote-Control applications can be used to charge the battery, but you do this at your own risk, and should always read the charger manufacturer’s instructions.

Our batteries are equipped with a Low Voltage Cutout safety feature, meaning that when discharged below a level of around 6v the battery will cut-out and register 0V. The charger on-board Rick can recover the battery by slowly trickle charging it.

Lithium polymer batteries (LiPo) can be dangerous if abused. Do not overcharge the battery or discharge it below the minimum safe voltage of 6.4v. Don’t disassemble or pierce the battery, leave it charging unattended or dispose of it in regular household waste or by burning.

Rick - Ratings and Maximums

Rick’s logic level is 3v3. The GPIOs and Serial lines are 5v tolerant but the I²C ports SDA1 and SCL1 are not. Rick has a maximum power output of 3A per each of the two 5v channel, maximum operational temperature of 50°C, thermal cut-out at 90°C and an on-board dual-cell 7.4v LiPo battery charger with __A peak charge current. Nominal battery voltage is between 6.4v and 18v. A discharged battery below 4.15v will not be charged by the board. Nominal charge voltage is between 8v and 12v. The two 5v regulators will be disabled when the battery voltage is below 6.4v, powering Rick off.

Rick has three on-board power regulators: two ST1S10 switch-mode 5v regulators, and one LD3905PU33R 3v3 LDO regulator. The battery charge IC is a mcp73213 dual-cell BCM Controller. See each manufacturer’s datasheet for exact ratings and capabilities.

One of the ST1S10 regulators powers the servo motor channels directly on the M0 through M8 pin-headers on Rick, with the name +5VM. Its 3 Amp capacity applies solely to the load on these motor channels, independently of any loads attached to the GPIO pins. The nominal voltage in our testing is 5.2v, (±0.2v). The voltage between the +5VM pins and MGND pins may be slightly less than this as each motor channel except M8 has a 0.1Ω current sense resistor between it and GND.

Do not connect the Motor’s MGND pins to the GND pins elsewhere on Rick or each-other, or any other attached grounded device as this may damage the control board. This is because each is connected to a current sense resistor and GPIO pin.

Rick has some basic reverse-polarisation protection, with two Q-FETs that prevent current flow when either the Battery BAT or Charger CHG are connected the wrong way around through the 4 pin JST connector P5. However the charging chip U7 is NOT protected and will be destroyed if the board is reversely polarised. If you’re not using the supplied connectors then take care to check polarisation.

The reverse polarity protection is also not designed to protect against sustained or out-of-nominal voltages in a reverse-polarised mode, i.e. anything above 8v. The protection is provided by two NTR4101PT1G Q-FETs, Q1 and Q2.

The 5v regulators have internal thermal-cutouts to protect against sustained high loads. They will cut out when at 90°C, dissipating a lot of power. Be careful and do not touch the PCB if driving high loads as it can cause injury. The Battery Charge chip also has a built in thermal cutout at 85°C. Frequent or sustained high loads could also permanently damage your control board.

Rick - Major Chipsets & Programming

Rick has two microcontrollers on-board, a STM32F446RE ARM Cortex M-4 core (U1 on the PCB), and an ESP8266 on a ESP-12 integrated WiFi module (U2 on the PCB).

The JTAG header P2 targets the STM32 and can be used to reflash it’s firmware with a compatible programmer (ST Link) and the ST’s boot select pin BOOT0 is broken out to testpoint TP6, while the testpoint TP7 connects the ESP’s GPIO0 pin, TP3 the TXDO port, TP4 the RXDI port on the ESP. These can be used to reflash the ESP’s firmware.

Also on-board are a MMA8652FC accelerometer and a small speaker attached to the ST’s DAC.

Note that the factory firmware on Rick’s main ST chip and ESP is not currently available so if you reprogram the board you won’t be able to restore it’s original firmware and function later.