Hardware FAQs¶

This section contains questions received related to hardware utilization and design of the MityDSP-L138 / MityARM-1808 family of SoMS.

I'm looking for the Port B of pwma1 (eHRPWM1B), where is it on the edge connector?¶

The EHRPWM1 peripheral has 3 pins, described below. Currently, you could use EPWM1A with this family of modules, but not the other two pins. Here is a description of where each of the peripheral pins are located:

1. EPWM1A : This is a PWM output and is pin-muxed with SPI1 chip select 1. It is brought out to the SO-DIMM connector (pin 51), and could be used as we don't need it by default.
2. EPWM1B : This is a PWM output and is pin-muxed with SPI1 chip select 0. We use this to read / access the on-board SPI flash for boot up as the chip select line. While it is brought to the SO-DIMM connector (marked as reserved, pin 53), it should not be used for other functions as it may corrupt the SPI-NOR device. We will use that pin for external programming at factory.
3. EPWM1TZ : This is an input signal, and is pin-muxed with AXR7 and a GPIO. On FPGA-based modules, it is used during FPGA initializion and is not brought out to an edge connector. On non-FPGA modules, it is used to detect low-battery status from on-board power managment RTC battery monitor.

Why does our custom carrier board will connect to a PC 100% of the time but only 50% or less to some switches and other devices?¶

This specific issue has not been in relation to the module in the past but the Phy (TLK100 in this case) located on a custom carrier board.

It has been observed that if a 50ppm crystal is used, within spec of the TLK100 component, in some cases a link will not be established to all devices. As such we recommend a 30ppm crystal (like the one used on our development board ECS-250-18-5PX-F-TR) or better.