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JerryR
Joined: 07 Feb 2008
Posts: 170
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| No SPI clocks |
 Posted: Tue Jul 15, 2025 9:58 am |
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Hi Group, thanks for your help on this-
I am using PCWH v5.093 to compile code for a PIC18F86J60. I am posting a small snippet of code below. I am using the hardware SPI1 to talk to two external SPI devices
The problem is that using either of the use_spi setups, results in no clocks being issue when attempting to write to a SPI device. The Data Out looks reasonable, however, but no clock pulses.
If I comment out both spi_setup statements, I can generate clock pulses on the clock pin (PIN_C3), so there's nothing in the hardware blocking the clock pin.
This is probably something very simple, but I just can't see it. Here's the code:
| Code: |
#include <18F86J60.h>
#device ADC=10
#FUSES NOWDT //No Watch Dog Timer
#use delay(crystal=25000000)
#use spi (MASTER, DI=PIN_C4, DO= PIN_C5, CLK= PIN_C3, BITS=8, MODE=0)
//#use spi (MASTER, SPI1, BITS=8, MODE=0)
void main()
{
setup_adc_ports(AN0_TO_AN1, VSS_VDD);
setup_adc(ADC_CLOCK_INTERNAL | ADC_TAD_MUL_0);
output_high(PIN_A3);
output_low(PIN_A3);
delay_us(10);
spi_write (0x50);
spi_write(0x00);
spi_write(0xFF);
delay_us(10);
output_high(PIN_A3);
while(TRUE)
{
}
}
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Ttelmah
Joined: 11 Mar 2010
Posts: 19898
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| Posted: Thu Jul 17, 2025 5:54 am |
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Key thing. With #use SPI, you have to use spy_xfer, not spi_write.
You are mixing commands from setup_spi, with those from #use SPI.
You should also specify a clock rate. The default is as fast as possible.
If you look in the manual, under #use spi, you will have listed at the
bottom of the page, the commands that work with this. |
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JerryR
Joined: 07 Feb 2008
Posts: 170
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| Posted: Thu Jul 17, 2025 7:45 am |
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Hello Ttelmah:
Thank you so much for your interest!
Yes, the current version of my code uses the correct method and calls, thanks for your clairification. I see from research you have been kind to mention this to quite a few in the group.
Should have posted this yesterday, but my problem with no clocks was solved. BAD LOGIC ANALYSER PROBE! I actually did have clocks using a scope.
Sorry to have raised the question to the group. Lessons here is don't always trust your equipment.
Best regards! |
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JerryR
Joined: 07 Feb 2008
Posts: 170
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| Posted: Sat Jul 19, 2025 11:37 am |
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All:
I am trying to use "#USE_SPI" commands to read a MCP23S08 inputs. I can successfully set output to a MCP23S17 using SPI_XFER command, but can't seem to understand how to read inputs on a MCP23S08.
I have used the older method "SETUP_SPI" sucessfully with both MCP23S08 and MCP23S17, however can't seem to get my head around using SPI_XFER to read data. Result of attempting to read always generates clocks and transfers "0".
Any help is much appreciated
My SPI setup is:
#use spi(MASTER, SPI1, BITS=8, BAUD=100000, MODE=0)
And my code to read MCP23S08 is:
| Code: |
#define IODIR 0x00
#define IPOL 0x01
#define GPINTEN 0x02
#define DEFVAL 0x03
#define INTCON 0x04
#define THERM_IOCON 0x05
#define GPPU 0x06
#define INTF 0x07
#define INTCAP 0x08
#define GPIO 0x09
#define OLAT 0x0A
/**************************************************************/
#define CONTROL_REG_VAL 0x40 //// these two defines are used here
#define CONTROL_REG_VAL_Read 0x41
#define GPIO_CONFIG_VAL 0x09 //// just to do very simple serial to parallel output transfer
void setup_MCP23S08(void){
int8 dummy;
output_low(THERM_CS);
delay_us(100);
dummy= spi_xfer(CONTROL_REG_VAL); // control register setup
dummy= spi_xfer (IODIR); // GPIO set to all inputs
dummy= spi_xfer (0xFF); // GPIO set to all inputs
delay_us(100);
output_high(THERM_CS);
}
//=============================================================================
int8 ReadFrom_Thermo_Exp(void)
{
int8 received_Therm_data;
int8 dummy;
output_low(THERM_CS);
delay_us(10);
dummy= spi_xfer(CONTROL_REG_VAL_Read);
dummy= spi_xfer(GPIO_CONFIG_VAL);
received_Therm_data = spi_xfer(0);
delay_us(10);
output_high(THERM_CS);
return received_Therm_data;
}
//=============================================================================
void WriteToExpanderPort(unsigned char data){
int8 dummy;
output_low(THERM_CS);
delay_us(10);
dummy= spi_xfer(CONTROL_REG_VAL); // control register setup
dummy= spi_xfer(GPIO_CONFIG_VAL); // GPIO configuration
dummy= spi_xfer(data); // value to I/O
delay_us(10);
output_high(THERM_CS);
}
//=============================================================================
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