The PEGMA boards and parts arrived this week. I was able to successfully populate the board, compile a test project and debug it using the STLINKV2 debugger from STMicro. Here are the bullets:
- Microcontroller: STMicro STM32F205VC (Originally planned on VG, 1MB flash is overkill)
- Buck Regulator: TPS62240 Stepping down 5Vusb to 3.3V for both V0 and V5 domains
- Addressable Latch: 74HCT259
- Compiler / Toolchain: Keil uVision / MDK 4.71.2
- Debugger: STMicro STLINKV2
- JTAG adapter: Olimex 20->10
Here are some of the tips I have and modifications I had to do in order to begin operation:
- The V0 domain is adjusted from a default operation of 1.8V to 3.3V by removing R4 and changing R52 to an 80k resistor.
- V6 is bridged to V0
- On the schematic/layout I have connected the two Vcap pins to Vdd. This is wrong, they each need a 2.2uF ceramic load capacitor for the internal regulator. The following picture is my solution to the problem:
- The system startup files generated by the STMicro clock excel spreadsheet worked fine. However it took me longer than it should have to realize that I needed to enable the clock to the port pins in order to make any modifications to the port (including wigging the line):
// Port C Configuration
RCC->AHB1ENR |= 0x00000004;//Enable port C interface clocks
GPIOC->MODER = 0x01151555; // IIIO IOOO IOOO OOOO
GPIOC->OTYPER = 0x00000000; // all push-pull
GPIOC->OSPEEDR = 0x00000000; // 2MHz output speed
GPIOC->PUPDR = 0; // No pullup or pulldown
Finally, we have a blinking board! I am looking forward to the next step, getting data out of the RS232 interface and then measuring the current consumption of the peripherals.
Schematics and layout are here. I will post the bill of materials as soon as I verify the functionality of the other components.