PCBs¶
Prototype (03/2021)¶
This is the first prototype board. All my prototypes are made with red soldermask. The board was used during the first year of development. The only real issue was two missing pullup resistors. Otherwise it worked as expected.
Revision 1 (03/2022)¶
After the hardware handshake of the PCB was confirmed to be working and the design of the mechanical part of the interface was finished, I’ve finalized the design of the board and ordered the first production units. The following two images show the top and bottom side of the board.
It’s a two layer design. The SMD parts were soldered by the manufacturer of the PCB. My job was to add the radial electrolytic capacitor and the sockets for the battery and the Teensy.
Revision 2 (01/2024)¶
Although the first generation of the P7001 USB interface worked very well, some minor problems came to light over time.
The first problem was that the interrupt detection did not work reliably when one of the DATA MODE buttons was pressed. It turned out that some signals on the front panel of the P7001 are clamped to 3V instead of 5V. And the level shifters on the USB Interface board do not reliably recognize 3V as “High” when they are referenced to 5V. This problem was solved by reducing the reference voltage of the affected level shifters.
The next problem was the Teensy’s on-board RTC. The standby current consumption of the RTC was much higher than expected. The data sheet of the Cortex-M7 processor states a typical standby current of 6.5µA - but without specifying a maximum limit. The result was that the CR2032 coin cell had to be replaced approximately every 3 months. The use of an RV-3028 RTC module reduced the standby current to about 45nA.
The last problem has a name: WP1000AF. This DPO system contains a set of factory modifications that add remote control functionality to the components. I added a second USB port on the P7001 USB Interface to be able to communicate with these other devices.
I’ve also added some more testpoints for debugging purposes.
