Hi, I am trying to interface LPC2138 with micrSD card(2-GB). I picked up the demo code for LPC2148 based on Flash File system(since LPC2138 is almost the same as LPC2148 except for usb device peripheral). On running the code: I can see the menu on UART(uart is working fine). But it gives error: " MMC/SD card init failed.. Insert Card and press key... "
In SPI driver file SPI_LPC214x.c, its using SPI1/SSP port. As for the hardware, connections are perfect and i am able to read and write sectors from sd-card(using another sector read/write code ofcourse).
functions present in SPI_LPC214x.c are:
*---------------------------------------------------------------------------- * SPI Driver Functions *---------------------------------------------------------------------------- * Required functions for SPI driver module: * - void spi_init () * - void spi_ss (U32 ss) * - U8 spi_send (U8 outb) * - void spi_hi_speed (BOOL on) *---------------------------------------------------------------------------*/
I have even set the heap size to 0x1000 and all other configurations are correct. Please help if i am missing something.
I am using RL-ARM v4.12 and MDK-ARM v4.21.
Regards, Salman Liaquat.
Max current sd-card can use = 60mA Max current processor can source = 4mA at Voh = Vdd-0.4 Yes, i was wrong there.
But we can use it to power EEPROM since it uses only 3mA max (AT24512). And i said surprised because i took that as general. "How did you got anything to work at all"
And i apologize if i got that wrong.
No hard feelings.
Regards, Salman.
"How did you got anything to work at all"
Ah, yes - I did mean, "anything to do with your SD-Crd"
Sure, with a very low-power load your could get away with powering it from a GPIO.
But, even with your EEPROM at 3mA, you're getting close to the stated 4mA point at which Voh droops to Vdd-0.4.
If Vdd is 3V, that's worse than 10% load regulation - so you'd better be very sure that your EEPROM can cope with that...
It's like connecting LEDs direct to port pins with no series resistor; it can be done - but it's really not to be encouraged...
Thanks for the useful information.
It is common to use a MOS-FET transistor to drive external equipment, when there is a need to be able to cut the supply to reduce the current consumption.
You can find many MOS-FET with very low on resistance. But you have to look carefully about what voltages you need to control them - for some designs, I have to switch the processor pin between actively driven low, and changed to input with a pull-up to 5V, because the used transistor can't be fully controlled with 3.3V. That obviously requires that the processor has 5V-tolerant inputs. In the case of LPC23xx, the input must be tristated or it will clip to 3.3V.