ST Microelectronics has released a new IC, the L6470, which includes a processor that controls micro-step operations and two DMOS “H” bridges for direct motor control. The chip seems easy to set up and use because it gives a host microcontroller direct access to internal registers and provides a series of high-level control instructions. Communications occur via an SPI port and four optional general-purpose I/O (GPIO) pins. STMicro also provides an evaluation kit, EVAL6470 ($US 63) and instructions in an application note, AN3103. You can download software that lets you exercise the board, but you supply a stepper motor.
So far, so good. But digging for more information led to a few problems.
First, you’ll need to buy an interface board to go between the EVAL6470 board and your host PC. The app note for the eval kit recommends either an IBU universal interface (IBU-UI) or a universal USB-to-serial communication interface (UUSCI) board. Then you must search the STMicro site for the REAL part numbers, STEVAL-PCC009V1 ($US 40) and STEVAL-PCC009V2 ($US 60) so you can decide which one to buy. The web site will direct you to a distributor, but it takes ten (10) mouse clicks to find one and the listing I found lacked a direct link to the distributor’s Web site. When I went to the distributor’s site, it didn’t recognize the part number. (The prices above come from Digi-Key; not listed by ST Micro as a distributor.)
Second, I downloaded the software for the EVAL6470 kit and ran it. It looks good, but it provides no guidance about what to use as preliminary settings for a motor nor does it create any source code based on settings you try and want to use. Maybe you write them down and pass them to a programmer. Likewise, the app note lacks a code flow chart, example code or information about what registers you MUST set and in what order.
Third, I looked on the STMicro web site for more information, such as an app note about how to use the L6470 chip and some code examples or a reference design. I found nothing except the IC data sheet and the AN3103 document.
I had hoped to write this column about the interesting L6470 chip, but information was so limited I gave up. The hardy engineers will find a data sheet for the L6470 at: www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00255075.pdf.
I don’t know why companies put roadblocks in the paths of customers who really want to evaluate or adopt an interesting device. When a company announces a product, it should have complete information ready to go. For a programmable device, the information should include examples of working code and explanations of how the code should operate, examples of simple applications, a short tutorial, etc. I understand companies want to get the word out, but why tick off possible customers who want complete information now? –Jon Titus
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