Recent Posts

1

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by Mechatrommer on Today at 10:53:50 am »

this is +1 imho in rigol, lets not forget, the 2 scopes discussed here got pros and cons.

Since the Siglent can into 2 Gsa/s, it could potentially be modded to support at least 800 MHz single-channel bandwidth, if there are no further limitations in digital signal processing and/or software. I don't recall anyone mentioning or trying this though.

i posted this earlier in this thread, some people said its very rare case. now we have 2 person asking for it so i'm not so rare, lets wait HAM fellows (names with numbers and who build their own radio) to chime in what they have to say, cheers.

2

Beginners / Re: Convert US standard 115V to International 230V

« Last post by radiolistener on Today at 10:50:55 am »

I believe the OP is just not qualified or certified and should not be making this type of decisions.

Completely agree. I wanted to politely bring the topic to the point that this is not easy decision for medical devices, because there are too many pitfalls which is not visible for non medical devices staff, but it appears that discussion going into wrong direction and my attempt was failed. Unfortunately some users decided that since they see simple and easy solution, they can just ignore medical devices specific and advocate their solution as the best solution and fiercely rejecting and criticizing all arguments against.

3

Beginners / Re: Why are thermal jumpers so expensive?

« Last post by tooki on Today at 10:45:26 am »

AFAIK AlN ceramic is used for ceramic knifes, though the requitements on the material could be a little different.

Nope. They’re zirconia (zirconium dioxide).

4

Test Equipment / Fluke PM6304 serial interface card RS232

« Last post by minolta on Today at 10:45:14 am »

Hello,
who has downloaded firmware (EPROM dump 27C1001 - OTP) for serial interface card RS232 (label on my eprom is PM9549 v 2.2 , but probably could be used similar version too).
Has anybody it?
I have unit that can not receive command, sending is OK. I have tested all possible, now I need to check FW.

I can upload main firmware (from the main board) v. 1.8 (EPROM 27C512) if somebody needs this.

Thank you for help!
..

5

Beginners / Re: Why are thermal jumpers so expensive?

« Last post by tooki on Today at 10:44:16 am »

Somewhat similar and a possible replacement could be a high resistance SMD resistor, like this: https://www.digikey.de/de/products/detail/vishay-beyschlag-draloric-bc-components/MCA1206MD1005BP100/11196602.
Price is similar, too: 33 cents in 1000s.

Regards, Dieter

Nonsense.

If you look at the datasheet, those resistors are made on Al₂O₃ ceramic, which is a very different material (aluminum oxide) from aluminum nitride. Aluminum oxide ceramic has thermal conductivity 2-10 times worse than aluminum nitride. Sure, either is better than the FR-4 PCB substrate, but they aren’t substitutes for thermal jumpers.

6

Other Equipment & Products / Re: Any opinions on the Aixun T420D?

« Last post by Tor Björn on Today at 10:43:43 am »

The c115 handle is connected directly to the station?

Yes, T115A handle with modified plug (with added "stanby" pin #4 and wire soldered to it) is connected directly to the host. Other end of the added wire must be connected to mast with bracket for T115A handle.
Yellow pair must be disconnected from mast's nut because this pair is "standby" pin signal of cradle's plug that also connected with T245/210 bracket and work with other channel (T245A handle in my case).
Sorry for my English, I can't explain it in any more detail or more clearly. 
...

Also I'm impressed you were able to get the device for so cheap. The cheapest I could find before aliexpress coupons was $210 for a T420 with single C245 handle.
Did you purchase a C115 handle version (T405) (which I saw for around $170 on the store you mentioned) and then bought a separate C245 handle?

Astray,

I bought a T420 in the T245A configuration at a bestboard Store for $161.

T420 in the T245A configuration (with T245A handle included, but without specific mast with hangle bracket for T115A handle) have a regular price for $181.48 at this store. I used a $20 coupon at "anniversary sale". But similar coupones or promocodes you can get it very often. Aliexpress holds different sales almost every month.

I bought the hangle (mast) with suspension (bracket) for the T115A separately at the same store, $6.67 with coins per pair. The T115A handle cost $5.75.

The T115A handle i bought at the China DIYPHONE Store aslo with coins. Regular price was $8.19.








Additional cheapest T245 handle I bought for $3.03 with coins just to have a "donor's pin".

7

Power/Renewable Energy/EV's / Re: Power supply EMC document is erroneous?

« Last post by Faringdon on Today at 10:42:22 am »

 

Add an EMI ground or chassis ground and connect a Y cap, it's no longer a two-lead supply.

Thanks,  and if a metal chassis is added to a DCDC, (ie its enclosure or heatsink) then its a very good idea to always connect Y caps from DCDC circuit to that  chassis anyway, for noise mitigation issues.

I dont  know if there is anyway that would say "i have not connected my metal enclosure  to the DCDC inside it and therefore i dont need a common mode filter"
....this wouldnt happen, you would always connect  DCDC circuit (usually its ground)  to chassis with y caps.

Now if the DCDC's enclosure was entirely all plastic, then it would be a different story. However, the problem is that a DCDC does not  "know" whether it has an enclosure or not. If it exists somewhere on the planet earth, then the DCDC "thinks" that the surrounding earth is its enclosure.....and due to the earths enormous mass, it has low effective conductivity, and so even if inside a plastic enclosure, the DCDC needs a common mode choke in its 2 lead input. The Y caps will be provided by the stray Y caps.

Here we see a common mode filter being designed for a DCDC

(3:10  onwards)

8

Projects, Designs, and Technical Stuff / Re: role of optocoupler for biasing drain of amplifiers

« Last post by xvr on Today at 10:36:14 am »

You don't need 24V, it should be 20V. This is a amplifier power. You didn't specify power voltage for amplifier in first post, but label it as +24V, so I decided that your amplifier powered by 24V.
There are 3 voltage source in scheme in total: logic side power supply, floating power supply (from DC/DC) and amplifier power supply. That is all, bo more power supplies (no any +24V)

9

Microcontrollers / STM32H7 CortexM4 USART DMA issue

« Last post by Diego_2024 on Today at 10:32:11 am »

I'm trying to use USART + RTS only + DMA(non circular, peripheral to memory, DMA1 Stram0) on STM32H755ZIT6's M4 processor. I and D caches are enabled on M7. My code is working on M7 but it does not works on M4.

// u8* dma_rx_buffer_ = (u8*)((u32)0x24000000);
// u8* dma_rx_buffer_ = (u8*)((u32)0x38000000);
u8* dma_rx_buffer_ = (u8*)((u32)0x30000000);

int main(void)
{
    //SCB_InvalidateDCache_by_Addr((u32*)dma_rx_buffer_, 14);
    error = HAL_UART_Receive_DMA(&usart2_dma_, dma_rx_buffer_, 14);
}

as you can see I'm setting RAM_D2's address to the dma_rx_buffer_, but I can't use SCB_InvalidateDCache_by_Addr on M4.

This is M7's Flash.ld

MEMORY {   
         RAM_D1 (xrw)   : ORIGIN = 0x24000000, LENGTH =  512K
         FLASH   (rx)   : ORIGIN = 0x08000000, LENGTH = 1024K
         DTCMRAM (xrw)  : ORIGIN = 0x20000000, LENGTH = 128K
         RAM_D2 (xrw)   : ORIGIN = 0x30000000, LENGTH = 288K
         RAM_D3 (xrw)   : ORIGIN = 0x38000000, LENGTH = 64K
         ITCMRAM (xrw)  : ORIGIN = 0x00000000, LENGTH = 64K
      }

this is M4's Flash.ld

MEMORY
    {
       FLASH (rx)     : ORIGIN = 0x08100000, LENGTH = 1024K
       RAM (xrw)      : ORIGIN = 0x10000000, LENGTH = 288K
       //RAM_D2 (xrw)   : ORIGIN = 0x30000000, LENGTH = 288K
       //RAM_D3 (xrw)   : ORIGIN = 0x38000000, LENGTH = 64K
    }

I also tried to add RAM_D1 and RAM_D2 inside M4's Flash.ld file and use it like this `attribute ((section(".RAM_D2"))) attribute ((aligned (32))) u8* dma_rx_buffer_;

but no result.

I also read DMA is not working on STM32H7 devices, but can't find solution.

P.S all configurations, including DMA are correct .

Also when I'm setting different addresses for dma_rx_buffer_ then I'm getting different data.

Do I need to add MPU region for CortexM4?

Update: Configured MPU region accrding DRAM addresses, but no result, with RAM_D1, RAM_D2 or RAM_D3.

/* Disable fault exceptions */
SCB->SHCSR &= ~SCB_SHCSR_MEMFAULTENA_Msk;

/* Disable the MPU and clear the control register*/
MPU->CTRL = 0;

MPU->CTRL = MPU_PRIVILEGED_DEFAULT | MPU_CTRL_ENABLE_Msk;

SCB->SHCSR |= SCB_SHCSR_MEMFAULTENA_Msk;

__DSB();
__ISB();

MPU->RNR = MPU_REGION_NUMBER8;

//MPU->RBAR = 0x24000000;
//MPU->RBAR = 0x38000000;
MPU->RBAR = 0x30000000;
MPU->RASR = ((uint32_t)MPU_INSTRUCTION_ACCESS_ENABLE << MPU_RASR_XN_Pos)   |
            ((uint32_t)MPU_REGION_FULL_ACCESS << MPU_RASR_AP_Pos)   |
            ((uint32_t)MPU_TEX_LEVEL0 << MPU_RASR_TEX_Pos)  |
            ((uint32_t)MPU_ACCESS_SHAREABLE << MPU_RASR_S_Pos)    |
            ((uint32_t)MPU_ACCESS_CACHEABLE << MPU_RASR_C_Pos)    |
            ((uint32_t)MPU_ACCESS_BUFFERABLE << MPU_RASR_B_Pos)    |
            ((uint32_t)0x00 << MPU_RASR_SRD_Pos)  |
            ((uint32_t)MPU_REGION_SIZE_32B << MPU_RASR_SIZE_Pos) |
            ((uint32_t)MPU_REGION_ENABLE << MPU_RASR_ENABLE_Pos);

What else can I do? 

10

Beginners / Re: Automatic golf ball dispenser

« Last post by soldar on Today at 10:30:29 am »

The reason why I want to move away from the leaver is that it moves the bucket. Gradually over time which means it loses alignment with the tee.

Make a base that holds the tee and the dispenser in place? Or just secure the dispenser in place?

And I hate it when people come in and propose a microcontroller for something which very clearly does not require a microcontroller at all. It's like someone with a hammer looking for nails to pound.