From 367fb9d40ef58d4ba4df156f41f356633319ae18 Mon Sep 17 00:00:00 2001
From: soypat <graded.sp@gmail.com>
Date: Sat, 29 Jan 2022 14:10:05 -0300
Subject: [PATCH] machine/rp2040: whole now correctly set at minimum 1 value
 for high frequency PWM

---
 src/machine/machine_rp2040_pwm.go | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/machine/machine_rp2040_pwm.go b/src/machine/machine_rp2040_pwm.go
index 525ea731..a355be4c 100644
--- a/src/machine/machine_rp2040_pwm.go
+++ b/src/machine/machine_rp2040_pwm.go
@@ -278,8 +278,14 @@ func (pwm *pwmGroup) setPeriod(period uint64) error {
 	rhs := 16 * period / ((1 + phc) * periodPerCycle * (1 + topStart)) // right-hand-side of equation, scaled so frac is not divided
 	whole := rhs / 16
 	frac := rhs % 16
-	if whole > 0xff {
+	switch {
+	case whole > 0xff:
 		whole = 0xff
+	case whole == 0:
+		// whole calculation underflowed so setting to minimum
+		// permissible value in DIV_INT register.
+		whole = 1
+		frac = 0
 	}
 
 	// Step 2 is acquiring a better top value. Clearing the equation: