Twenty years ago, foundations were laid for the Arduino UNO. It was designed around the popular Atmel (Microchip) ATMega328p microcontroller.
Without question, this open-source project changed the nature of microcontroller education and DIY electronics.
It enjoys tremendous community support with an ever-growing code base, education materials, and a growing list of derivative hardware.
Last year, Arduino introduced the latest edition of the classic UNO featuring a Renesas R7FA4M1AB3CFM#AA0 packaged in a 64-pin LFQFP (10x10) SMD package. The new UNO R4 WiFi and Minima are sure to be successful as they leverage the classic UNO form factor while providing a powerful 32-bit upgrade.
This engineering brief serves as a guide for the advanced learner who has reached the limits of the UNO R4 and desires to transition to the next level while staying within the Renesas family. We explore two solutions: one small (Figure 1) with the Seeed XIAO RA4M1 and the Arduino Portenta C33 with more power (Figure 2).
Figure 1: Image of the Seeed XIAO RA4M1 installed on a breadboard.
Tech Tip: Let’s take a moment to thank the army of programmers associated with the Renesas and Arduino communities. I wonder how many human-life-equivalent hours have been dedicated to the effort. We all benefit from their work.
Figure 2: Image of the powerful Arduino Portenta C33 used to control a servomotor.
Why should we stay within the Renesas family?
A key consideration is to leverage the work of the greater Arduino community. The 8-bit ATmega328p is a perfect example. This little microcontroller has received an extraordinary amount of attention. Therefore:
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The bugs have been identified and worked out.
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Extensive education material is available.
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Forums provide a wealth of information.
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Tens of thousands of projects have been constructed, many with detailed descriptions on the ‘Net.
In short, the ATMega328p has been embraced by the community.
Will this happen with the Renesas processor? That question will be answered in the next decade. At this point, we can say there is inertia in that direction.
An example of this work is shown in Figure 3, where the Seeed microcontroller is used to drive a pair of RC servos. In this example, we leverage the community work that ported the RC Servo library to the Renesas RA4M1.
Figure 3: Image of the Seeed XIAO RA4M1 controlling a pair of RC servos. The Digilent Discovery ADP2230 was used to observe the driver waveform.
Transition to a smaller form factor
The Seeed XIAO RA4M1 as shown in Figures 1 and 3 provides a smaller alternative to the Arduino UNO R4. It features a nearly identical Renesas R7FA4M1AB3CNE#AA0 housed in a 48-pin 48-HWQFN (7x7) SMD package. This processor appears to have the same core as the 64-pin LFQFP featured on the Arduino WiFi and Minima. It has the same speed, flash memory, RAM, and EEPROM. However, it does have 31 I/O pins as compared to the 49 I/O pins available on the larger device. This is a minor concern given the desire to move to a small form factor.
Additional information may be found on the Seeed RA4M1 Wiki. This includes a guide for installing the driver so that the board may be programmed directly from the Arduino IDE.
Tech Tip: The Seeed XIAO RA4M1 features 3.3 VDC I/O while the Arduino UNO R4 pins have a 5.0 VDC output voltage. Be sure to adjust your circuit accordingly.
Transition to more power
The Arduino Portenta C33 (Figure 2) is available for those wishing for a closely related Renesas RA6M5 processor.
Strictly speaking, the Renesas RA6M5 is not in the same family as the RA4M1. However, it’s been my experience that Renesas and Arduino follow similar patterns between devices. Stated another way, as we open the hood and inspect the underlying software and hardware, we find similarities. These similarities are sure to be leveraged by the greater community to make cross-compatible design solutions.
I’ve described the C33 in previous articles such as this brushed motor controller. When I say more powerful, consider that the C33 was simultaneously running FreeRTOS, an Ethernet server, a serial interface, a PID controller to control a DC motor, and was responsive to a high-speed quadrature encoder
I’ll admit, programming isn’t my greatest strength—I’m more of an electronics generalist. Still, I suspect the Portenta C33 is capable of much greater projects. For example, it would be fun to program the C33 to conduct the operations of a three-phase motor controller.
Tech Tip: The ARM microcontrollers feature a hardware device known as the Nested Vectored Interrupt Controller (NVIC). It is responsible for determining the priority of each interrupt. For example, it decides if the FreeRTOS time tick is more important than an interrupt on change pin.
We can’t overstate the importance of community support for these little but important details. As people gravitate to the Arduino UNO R4 and Renesas platform, we can expect the knowledge base to grow, thereby making these devices even easier to use.
Parting thoughts
The Arduino UNO R4 is the latest offering from Arduino. It features a powerful 32-bit Renesas RA4M1 processor. Moving forward we can anticipate a growing level of community support for the classic form factor.
It’s good to know that developers have options that allow them to stay within the Renesas ecosystem while leveraging the Arduino community. This includes the small devices such as the Seeed XIAO RA4M1 and the powerful Arduino Portenta C33.
Horses for courses.
Please share your thoughts and experiences on this wonderfully complex topic.
Best wishes,
APDahlen
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About this author
Aaron Dahlen, LCDR USCG (Ret.), serves as an application engineer at DigiKey. He has a unique electronics and automation foundation built over a 27-year military career as a technician and engineer which was further enhanced by 12 years of teaching (interwoven). With an MSEE degree from Minnesota State University, Mankato, Dahlen has taught in an ABET-accredited EE program, served as the program coordinator for an EET program, and taught component-level repair to military electronics technicians. Dahlen has returned to his Northern Minnesota home and thoroughly enjoys researching and writing articles such as this.