Curiosity HPC v2: a short review

Today, I will show you a development board from Microchip that I will use in programming lessons on eight-bit PIC microcontrollers. This board is called Curiosity HPC and has part number DM164136. At TME, where I usually shop, Curiosity HPC costs around $65 plus VAT. Microchip boards have always been expensive. When I selected this board, I looked for a compromise between the ability to develop complex projects and the price I would have to pay.

Curiosity HPC allows the development of projects with eight-bit PIC microcontrollers in 28- or 40-pin packages. I will use the second hardware version of this board in my projects. This hardware version comes with a current limiting circuit that can be drawn from the USB port. This limiting circuit is absent in the first version of the board.

Therefore, I recommend you avoid the old version because there is a higher chance of damaging the USB port if you make a mistake and cause a short circuit. The second significant improvement over the first version of the board is the implementation of a USB-to-serial converter, which allows us to connect to the board with a program like TeraTerm.

Old version (Rev 1) of Curiosity HPC.

The programmer side: PKOB4 and power circuits

I'll start introducing the board by going from left to right, and we see two different areas of this board. On the left side, we have the PKOB4 (PicKit On Board 4) programmer, a simplified version of the PICKIT4 programmer. Also, on the left side, we have the power circuits, and we notice that this board can only be powered from the USB port. The maximum current that can be drawn from the USB port is limited by a MIC2042 integrated circuit.

If we study the schematic of the Curiosity HPC board and the MIC2042 datasheet, we can calculate the current limit at 840mA. Given that the MIC2042 has a 20% tolerance, the current limit can vary from board to board in the range of 650mA to 1.03A.

These values exceed the limits set by standards for USB1 and USB 2.0, and only USB3 ports can deliver such high currents.

The same MIC2042 circuitry also monitors the supply voltage and generates a Power Good signal, which is sent to the microcontroller in the PKOB4. The development board will operate correctly if the supply voltage is above 4.4 V and will be stopped if the supply voltage drops below 4.1 V.

All these protections should ensure we don't destroy the USB port if we make the wrong connections and have a short circuit. However, the practice has often shown me that the protections aren't fast enough to protect the USB ports, and, like with the Arduino boards, I recommend using a separately powered USB hub between the PC and the board. That way, in case of problems, it's preferable to damage a cheap USB hub instead of destroying the USB ports in the computer.

On the power side, we also have a second voltage regulator that takes the 5V voltage from the USB and generates the 3.3V voltage. With a jumper, we can change the supply voltage of the microcontroller we are programming as needed.

Also, in the programmer area, we have the reset button. It is connected to the microcontroller in the programmer, so pressing the button will reset both microcontrollers. Here, we also find two LEDs used to display various error codes.

Next, we see the white line separating the programmer area from the area dedicated to the microcontroller we will be programming. Supply voltages and the ground cross this line. Also, we have the signals needed to program the microcontroller and the serial port. The signals for programming are PGD or Program Data, PGC or Program Clock, and /MCLR or Memory Clear or Reset. /MCLR is a pin with multiple functionalities to reset and switch the microcontroller to programming mode.

Curiosity HPC uses only LVP or "Low-Voltage Programming", which allows the microcontroller to be programmed using the VDD supply voltage.

Note here that all new PIC microcontrollers come with LVP active. We cannot exit LVP mode as long as we use LVP programming. To get the microcontroller out of LVP mode, we need a programmer that uses HVP, or High Voltage Programming. This way, we can't make a mistake and end up with a microcontroller that can no longer be programmed.

The two serial port lines are marked RX and TX. After loading the program into the microcontroller's memory, the programmer acts as a USB-to-serial converter. 

The microcontroller side

On the right side of the board, we will find the microcontroller that we will program and use in all the programming lessons.

The board I'm using came equipped with a PIC18F47Q10, a microcontroller based on the PIC18 core, with 83 instructions and 31 stack levels. The internal oscillator can be configured up to a frequency of 64 MHz. PIC microcontrollers need four clock cycles to execute an instruction.

Memory includes 128 KB FLASH memory for storing code, 3728 bits of SRAM memory, and 1024 bytes of EEPROM memory.

Among the peripherals I will mention here:

• 10-bit resolution analog-to-digital converter
• Two I2C/SPI communication ports
• Two EUSART ports
• 5-bit resolution digital-to-analog converter
• Two comparators
• Two 10-bit resolution PWM ports
• Three 8-bit resolution timers
• Four 16-bit resolution timers

The PIC18F47Q10 microcontroller is part of the new generation of PIC microcontrollers equipped with Peripheral Pin Select.

PPS allows for a flexible allocation of digital I/O peripheral pins to the physical pins of the microcontroller. In older 8-bit devices, a peripheral was assigned to a specific pin (example: PWM1 output on pin RC5). PPS gives the developer a broader basis for selecting the output and input pins to which a peripheral can be connected.

In addition to the microcontroller provided with the board, in a 40-pin package, we also have the option of using 28-pin PIC microcontrollers. Inside the 40-pin socket, we find a second 28-pin socket. I'll show you the picture because removing the microcontroller from the board and inserting it back in without bending or breaking a pin is difficult.

When we use microcontrollers in a 28-pin package, we won't be able to take advantage of all the features offered by the Curiosity HPC board.

Also, in this area of the board, we find a potentiometer, two buttons, and four LEDs. One can deactivate them by removing these little solder blobs.

The Curiosity HPC board comes with two mikroBUS sockets, an open standard developed by the Serbian company MikroElektronika for their extension modules, called Click boards (TM). These modules have been designed to offer SPI, I2C, UART, PWM, ADC, reset, interrupt, and power (3.3V and 5V) for the extension modules in a small footprint.

More than a thousand Click board modules are currently available, performing various functions. I use these kinds of modules a lot, and I'm a big fan of the mikroBUS system, especially as I can use adapters to use   Click modules on Arduino and other development systems I work with. Thus, I have a unified system of extension modules.

For those who have sensors from other manufacturers, there are two modules in the Click boards range with connectors from which we can run cables to our modules. One is with pins; the other has terminal blocks for wires. There is also a Proto Click, which we can use as an adapter for various small modules.

Click boards to expand the connectivity of Curiosity HPC

For those who want to avoid using mikroBUS modules, there is the option of using the two extension connectors located next to the microcontroller. From where we can run wires to a breadboard on which we develop our projects. By their nature, these breadboards are intended for building non-permanent projects. Suppose we want to achieve a permanent assembly. In that case, there are prototype development boards with a similar layout of connections as breadboards, so we can use such boards and make permanent connections for our project.

To make working with this board easier, I have prepared a pinout where I have shown the PIC18F47Q10 microcontroller. I have drawn its capsule and shown how each pin connects to the various elements on the Curiosity HPC board and the mikroBUS sockets. I used yellow for the elements on the Curiosity board, pink for the connections to the programmer, green for the connections to the first mikroBUS socket, and purple for the second one.

As you can see, several elements share some pins. In certain instances, like with I2C and SPI interfaces, this overlapping is not problematic. However, a conflict arises between serial communication with a PC and serial communication with the first mikroBUS module. To mitigate this issue, one viable strategy is to refrain from inserting modules that require serial communication into the first mikroBUS socket.

I'd like to add a note on the terminology for SPI pin labeling. Initially, SPI signals were known as MISO (Master In Slave Out), MOSI (Master Out Slave In), SCK (the clock signal), and CS (Chip Select). However, due to the politically sensitive and dehumanizing nature of the terms "master" and "slave," these have been updated. The terminology has shifted to "controller" in place of "master" and "peripheral" replacing "slave." Accordingly, the pin labels have also been revised to COPI (Controller Out Peripheral In) and CIPO (Controller In Peripheral Out), reflecting this change.

Similarly, the terminology for the I2C interface has been updated. "Controller" now replaces the term "master," and "target" is used in place of "slave," reflecting a shift towards more inclusive language.

In my context, thankfully, slavery is a historical concept encountered only through literature. I don't have a direct personal connection with the terminology discussed. I have to say, though, I'm not too fond of the new terminology because it creates confusion. 

While I'm open to adopting the term "controller," the distinction between "peripheral" in one communication protocol and "target" in another, despite referring to similar concepts, seems problematic. The challenge is compounded by the extensive legacy of articles, documentation, and educational materials that utilize the traditional terminology. Additionally, the transition poses practical difficulties, particularly when interfacing older development boards, which use MOSI/MISO labels, with newer ones adopting COPI/CIPO terminology, potentially leading to confusion during connections.

While I did not set these standards, I recognize the importance of adhering to them. Therefore, I plan to use both the new and old terminologies concurrently, particularly when working on projects that integrate modules following both naming conventions. This approach will continue until there is a universal shift away from the traditional "master/slave" terminology.

Conclusion

Given its robust hardware capabilities, the Curiosity HPC board is intricately designed for developing 8-bit PIC microcontroller projects, particularly when utilizing MikroElektronika's Click Board modules.

Its design, which accommodates both 28- and 40-pin PIC microcontrollers and significant upgrades compared to the first hardware version, makes it a robust platform for developing complex projects.

Despite its relatively high cost, the board's features, including the integration with mikroBUS sockets, justify the investment by providing enhanced versatility and ease of use. Curiosity HPC will prove its utility as a valuable education tool for those looking to deepen their understanding and skills in 8-bit PIC microcontroller programming, offering a balance between cost and functionality that is hard to match among PIC microcontroller development boards.

In conclusion, considering these hardware features, Curiosity HPC is a board complex enough to develop 8-bit PIC projects, especially if we use Click Board modules from MikroElektronika.

Note: I originally wanted to write this review for my new YouTube channel, but there was too much talk and too little movement in the video, so I transformed it into a blog post.