December 07, 2021, 08:23:26 pm

STM32-P407 DAC Problem

Started by itisnt, December 17, 2012, 12:54:51 am

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itisnt

Hi Guys

I have a simple Program witch enables the DAC-Channel 1 on PA4 and generates with a couple of 8-bit values analog values from 0 - 3V.
This runs fine on a STM32-Discovery board. But when i use the same program on the P407 board, i only get values from 0V - 1.6V ?
It's absolutely the same program with just the clock correction (8mhz on discovery and 25mhz on P407).

- Power comes from a external 5V 850mA source
- No Jumper where changed.
- Power-Sel Jumper is still on 1-2 position

I'v also tested the DAC_SignalGeneration example from the "STM32F4xx_DSP_StdPeriph_Lib_V1.0.1" Library from ST. The same here in the "EscalatorConfig" Part.

Any ideas, what that could be ?

Regards,

Daniel

LubOlimex

Hey Daniel,

Both DACs (PA4, PA5) are connected to peripherals. The one you used is connected to the camera. The other one is connected to the display. It is not correct to expect 0-3V without disconnecting the mentioned peripheral on the DAC line used. This is so because the peripherals would draw power.

The camera can be physically disconnected and that would ensure proper levels on PA4. There is also a software workaround involving the CAM_PWR line.

Best regards,
Lub/OLIMEX
Technical support and documentation manager at Olimex

itisnt

Hey Lub

Thanks a lot for that answer. Then i will disconnect the camera, and everybody is happy.

Regards,

Daniel