Discovery - disabling onboard peripherals

[stefanskos9]

Posted on June 26, 2012 at 03:38

Hi,

Bit of a noob question here, but I'm planning to use a STM32F4DISCOVERY board purely for its onboard programmer and also to save space on my PCB (will connect via header). Unfortunately this means i get a bunch of things i don't really want connected to my chip - accelerometer, mic, audio DAC, etc. I have ADC/USART connections which i wish to make, but some of these pins are already connected to the peripherals. Question is, can I disable these peripherals or do I need to cut the trace? I dont actually have the board yet. For example from the schematic I see ADC PC3 (ADC123_IN13) is connected to a whole bunch of resistors and caps for the audio module. This will obviously effect my reading. Probably USART3 is the easiest to get to and only has a green LED on PD12 (USART3_RTS), will this effect its performance? What do other people do? Or should I just put the cpu on my pcb and buy an external programmer? Thanks for your help. I'm guessing i'll need to cut the traces but just wondering if there's an easier way.

[Tesla DeLorean]

Posted on June 26, 2012 at 04:43

The easiest route is to pick unused pins. Next is to find ones that don't conflict, or can be shared. Finally just desolder unwanted parts and remove them.

Part of the trick with designing with the STM32 series is to figure out what peripherals you want to escape, and what combinations will work. You won't be able to get the entire peripheral set out. USART3 is probably the most useful to escape from the board, as it supports the System Loader for programming blank chips. Check on places like eBay for STM32F2 or F4 boards that just escape chip pins to headers. They are often more expensive than the Discovery boards, but a whole lot cheaper than spinning a PCB design. The ST-Discovery boards are cheap and aimed at quick mash-up or prototype work, given the low cost it's hard to feel guilty about hacking parts off them, or tacking on other boards, sockets, or connectors.

[stefanskos9]

Posted on June 26, 2012 at 09:16

Hi,

Thanks clive1 for your reply. I looked on eBay but nothing suits at the moment. I will just desolder or cut the traces (dont want aerials). 🙂 rgds

[Tesla DeLorean]

Posted on June 26, 2012 at 16:19

I guess it would depend a lot on what your drivers are for using the F4, vs the F1 or F2 designs.

The F0-Discovery has very little in the way of external periphery, but may be underpowered for your application. Here are some example eBay boards with mostly break-out functionality.

http://www.ebay.com/itm/STM32F103ZET6-144-PIN-Core-Board-AVR-ARM-51-for-Arduino-Project-DIY-/330658037012?pt=BI_Robotics&hash=item4cfcc13d14

http://www.ebay.com/itm/Core407V-STM32F407VET6-STM32-ARM-Cortex-M4-Development-Board-Full-I-O-Expander-/261045971937?pt=LH_DefaultDomain_0&hash=item3cc78d6be1

http://www.ebay.com/itm/UET-STM32F207ZGT6-144-pin-core-board-/320738521439?pt=US_Ham_Radio_Transmitters&hash=item4aad81715f

External memories

http://www.ebay.com/itm/STM32F407-417ZG-module-HY-STM32F4xxCore144-Core-Dev-Board-/170818749248?pt=BI_Electrical_Equipment_Tools&hash=item27c5974340

Providing links for illustration, not specific recommendations. Personally I haven't had problems getting boards from Thailand, China and Hong Kong, just have to be realistic about the ship times.

[Andrew Neil]

Posted on June 26, 2012 at 20:39

''can I disable these peripherals''

Yes - most (all?) have solder-bridge links that you can un-link to disconnect the peripheral. ''do I need to cut the trace?''   (generally) no - see above!''I dont actually have the board yet.'' You can download the User Manual - it has schematics and lists all the links. In fact, you'll have to download it anyhow - there is nothing shipped with the board. If you search the forum, there's also a guy who has prepared and kindly published a spreadsheet with all the connection info...