We are running a survey to help us improve the experience for all of our members. If you see the survey appear, please take the time to tell us about your experience if you can.
I've read the posts here, and searched the internet. How does one READ from a slave using a processor with SPI? I can write just fine. I tell my slave that I'm going to write, then I put bits on the bus, and the processor sends out the data with each clock. For reading, I tell my slave that I'm going to read... then when I read the input buffer, it is just equal to my "I'm going to read" instruction fed back to me. How do I tell the processor to start sending clocks for a read so that my slave will start shifting out data?? If I can provide more details, please ask. Any reference to C code that reads from a slave over SPI, or any comments about what my stupid mistake is, would be greatly appreciated. Thanks
Check the datasheet for the device you are using. For example, the Analog Devices ADuC812 states: "SPI is an industry standard synchronous serial interface that allows eight bits of data to be synchronously transmitted and received simultaneously, i.e., full duplex." and "In master mode, the SCLOCK pin is always an output and generates a burst of eight clocks whenever user code writes to the SPIDAT register." So, it sounds like you should receive SPI data from a slave when you first select the slave and then transmit a byte. Jon
Thanks, I've been thinking about that. Since data is sent and received at the same time, I could send "dummy" bits to get the clock going. However, my slave has one pin for input/output and this is switched by another chip. I've been having problems with overwriting data... but now that you mention it, I could write dummy bits to a disabled (disconnected from the slave input/output pin) MOSI line, and read in my data on an enabled MISO line. Hmm, I hope it works... Thanks for the help!
We are developing a project with ADuC812 in Federal University of Campina Grande, and I wish to communicate two microconverters using the SPI. I have some problems becouse with the flag ISPI becouse the flag don't change in the end of the transmission. Is necessary to use any interrupt routine for to use the flag ISPI? I need more information about this problem. I am sending my code used for transmit a caracter C and to monitore the change in flag ISPI. I noted that the flag don't change. Please look my code, is it wrong? Send me some information, and if possible change the code. If possible, answer me how I may to transmit a byte in a master( micriconverter) for a slave(microconverter). Sincerely, Jaidilson Jó. //Master #include <aduc812.h> #include <stdio.h> #define SPICON_MR 0x33 sbit P3_5 = 0xB5; sbit P3_4 = 0xB4; int i; void main () { P3_5 = 1; // Serial SCON = 0x50; TMOD = 0x20; TR1 = 1; TH1 = 0xFD; IE2 = 0x01; IE = 0x81; TCON = 0x01; IT0 = 1; SPICON = SPICON_MR; P3_5 = 0; P3_4 = 0; SPIDAT = 'C'; //writing a character C for to transmit while((SPICON & 0x80) == 0) { TI=0; SBUF='\n'; while(TI != 1){} printf("%\n",SPICON); while(TI!=1) { } } TI=0; SBUF='\n'; while(TI != 1){} printf("%\n",SPICON); while(TI!=1) { } P3_4 = 1; P3_5 = 1; }