As RAMPS-FD v2 is nearing tape out, I have been wondering if we can take advantage of some of the faster ARM cores around, and get some more bang for the buck.
Of particular interest are the Cortex-M4 with hardware FPU, and other DSP like features. The two I have been looking at closely based on availability and cost are STM32F4xx and LPC43xx.
The STM32F407VET6 has an M4F core at 168MHz, 1MB Flash 192KB RAM, USB in a 100 pin LQFP package, about $11 one off. There is a also a dev board for $15, the STM32F4Discovery. For an extra $2 there is an ethernet variant.
So that would be a pretty fast chip compared to the Due.
NXP have something even more interesting, a dual core chip with a Cortex M4F and a Cortex M0. Both clock at 204Mhz. The LPC4333JBD is 144 LQFP also about $11.
The dual core architecture allows the M0 to be dedicated to driving the steppers and doing acceleration profiles, while the M4 handles the user interface and number crunching. We could use separate M4F and M0/3, but having them in one die means they can share memory and avoids the need for high speed comms interface, and one package is easier to deal with physically.
Another advantage of these chips is that some of them have an external memory interface, which allows several MB of RAM to be attached. This would allow some very long lookahead buffers.
Overall, I think the LPC4300 series is the best available at the price point and the most interesting at the moment. Freescale also have some good value chips in the M4/M0 range.
From the software point of view, NXP, Freescale and STM all seem to be throwing their hat into the mbed arena. If anyone hasn't used mbed, it's like a much better version of Arduino.
Of particular interest are the Cortex-M4 with hardware FPU, and other DSP like features. The two I have been looking at closely based on availability and cost are STM32F4xx and LPC43xx.
The STM32F407VET6 has an M4F core at 168MHz, 1MB Flash 192KB RAM, USB in a 100 pin LQFP package, about $11 one off. There is a also a dev board for $15, the STM32F4Discovery. For an extra $2 there is an ethernet variant.
So that would be a pretty fast chip compared to the Due.
NXP have something even more interesting, a dual core chip with a Cortex M4F and a Cortex M0. Both clock at 204Mhz. The LPC4333JBD is 144 LQFP also about $11.
The dual core architecture allows the M0 to be dedicated to driving the steppers and doing acceleration profiles, while the M4 handles the user interface and number crunching. We could use separate M4F and M0/3, but having them in one die means they can share memory and avoids the need for high speed comms interface, and one package is easier to deal with physically.
Another advantage of these chips is that some of them have an external memory interface, which allows several MB of RAM to be attached. This would allow some very long lookahead buffers.
Overall, I think the LPC4300 series is the best available at the price point and the most interesting at the moment. Freescale also have some good value chips in the M4/M0 range.
From the software point of view, NXP, Freescale and STM all seem to be throwing their hat into the mbed arena. If anyone hasn't used mbed, it's like a much better version of Arduino.
